Monthly Archives: December 2019

I2C Bus Sniffing with Excel VBA

In my never-ending quest to figure out why my I2C connection to an MPU6050 dies intermittently, I decided to try and record the I2C bus conversation to see if I can determine if it is the MPU6050 or the microcontroller goes tits-up on me.

Of course, this adventure turned out to be a LOT more complicated than I thought – I mean, how hard could it be to find and run one of the many (or so I thought) I2C sniffer setups out there in the i-verse? Well, after a fair bit of Googling and forum searches, I found that there just aren’t any good I2C sniffer programs out there, or at least nothing that I could find.

I did run across one promising program; it’s a Teensy 3.2 sniffer program written by ‘Kito’ and posted on the PJRC Teensy forum in this post. I also found this program written for the Arduino Mega. So, I created a small Arduino Mega test program connected to a MPU6050 using Jeff Rowberg’s I2CDev library.

/*
    Name:       I2C_SNIFFER_TEST_PGM.ino
    Created:	12/20/2019 9:56:20 PM
    Author:     FRANKNEWXPS15\Frank
*/
#include <elapsedMillis.h>
#include <PrintEx.h> //allows printf-style printout syntax
#include "MPU6050_6Axis_MotionApps_V6_12.h"  //changed to this version 10/05/19
#include "I2Cdev.h" //02/19/19: this includes SBWire.h
#include <NewPing.h> //added 01/15/15
#pragma endregion INCLUDES

StreamEx mySerial = Serial; //added 03/18/18 for printf-style printing
elapsedMillis 	sinceLastNavUpdateMsec; //added 10/15/18 to replace lastmillisec

//MPU6050 mpu(0x69); //06/23/18 chg to AD0 high addr on 2-motor robot
MPU6050 mpu(0x68); //06/23/18 chg to AD0 high addr on 2-motor robot


#pragma region MPU6050_SUPPORT
uint8_t mpuIntStatus;   // holds actual interrupt status byte from MPU. Used in Homer's Overflow routine
uint8_t devStatus;      // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize;    // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount;     // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer

						// orientation/motion vars
Quaternion q;           // [w, x, y, z]         quaternion container
VectorInt16 aa;         // [x, y, z]            accel sensor measurements
VectorInt16 aaReal;     // [x, y, z]            gravity-free accel sensor measurements
VectorInt16 aaWorld;    // [x, y, z]            world-frame accel sensor measurements
VectorFloat gravity;    // [x, y, z]            gravity vector
float euler[3];         // [psi, theta, phi]    Euler angle container
float ypr[3];           // [yaw, pitch, roll]   yaw/pitch/roll container and gravity vector
int GetPacketLoopCount = 0;
int OuterGetPacketLoopCount = 0;

//RTC/FRAM/MPU6050 status flags
bool bMPU6050Ready = true;
bool dmpReady = false;  // set true if DMP init was successful
volatile float global_yawval = 0; //updated by GetIMUHeadingDeg()
const uint16_t MAX_GETPACKET_LOOPS = 100; //10/30/19 added for backup loop exit condition in GetCurrentFIFOPacket()
uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops = MAX_GETPACKET_LOOPS); //prototype here so can define a default param
bool bFirstTime = true;
#pragma endregion MPU6050 Support


const int NAV_UPDATE_INTERVAL_MSEC = 200;

void setup()
{
	Serial.begin(115200);
	Wire.setClock(100000);

	// initialize MPU6050 added 09/03/18
	Serial.println(F("Initializing MPU6050 ..."));
	mpu.initialize();

	// verify connection
	Serial.println(F("Testing device connections..."));
	Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

	Serial.println(F("Initializing DMP..."));
	devStatus = mpu.dmpInitialize();
	// make sure it worked (returns 0 if successful)
	if (devStatus == 0)
	{
		//12/06/19 no longer needed; cal vals already acquired
		// Calibration Time: generate offsets and calibrate our MPU6050
		//mpu.CalibrateAccel(6); 
		//mpu.CalibrateGyro(6);
		//Serial.println();
		//mpu.PrintActiveOffsets();

		// turn on the DMP, now that it's ready
		Serial.println(F("Enabling DMP..."));
		mpu.setDMPEnabled(true);

		// set our DMP Ready flag so the main loop() function knows it's okay to use it
		Serial.println(F("DMP ready! Waiting for MPU6050 drift rate to settle..."));
		dmpReady = true;

		// get expected DMP packet size for later comparison
		packetSize = mpu.dmpGetFIFOPacketSize();
		bMPU6050Ready = true;
		mySerial.printf("\nMPU6050 Ready at %2.2f Sec\n", millis() / 1000.f);
	}
	else
	{
		// ERROR!
		// 1 = initial memory load failed
		// 2 = DMP configuration updates failed
		// (if it's going to break, usually the code will be 1)
		Serial.print(F("DMP Initialization failed (code "));
		Serial.print(devStatus);
		Serial.println(F(")"));

		bMPU6050Ready = false;
	}

	sinceLastNavUpdateMsec = 0;

}

void loop()
{
	if (sinceLastNavUpdateMsec >= NAV_UPDATE_INTERVAL_MSEC)
	{
		sinceLastNavUpdateMsec -= NAV_UPDATE_INTERVAL_MSEC;
		mpu.testConnection();
		mpu.resetFIFO();

		for (size_t i = 0; i < 10; i++)
		{
			int count = mpu.getFIFOCount();
			delay(10);
		}
	}
}

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Name: I2C_SNIFFER_TEST_PGM.ino

Created: 12/20/2019 9:56:20 PM

Author: FRANKNEWXPS15\Frank

#include <elapsedMillis.h>

#include <PrintEx.h> //allows printf-style printout syntax

#include "MPU6050_6Axis_MotionApps_V6_12.h" //changed to this version 10/05/19

#include "I2Cdev.h" //02/19/19: this includes SBWire.h

#include <NewPing.h> //added 01/15/15

#pragma endregion INCLUDES

StreamEx mySerial = Serial; //added 03/18/18 for printf-style printing

elapsedMillis sinceLastNavUpdateMsec; //added 10/15/18 to replace lastmillisec

//MPU6050 mpu(0x69); //06/23/18 chg to AD0 high addr on 2-motor robot

MPU6050 mpu(0x68); //06/23/18 chg to AD0 high addr on 2-motor robot

#pragma region MPU6050_SUPPORT

uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU. Used in Homer's Overflow routine

uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)

uint16_t packetSize; // expected DMP packet size (default is 42 bytes)

uint16_t fifoCount; // count of all bytes currently in FIFO

uint8_t fifoBuffer[64]; // FIFO storage buffer

// orientation/motion vars

Quaternion q; // [w, x, y, z] quaternion container

VectorInt16 aa; // [x, y, z] accel sensor measurements

VectorInt16 aaReal; // [x, y, z] gravity-free accel sensor measurements

VectorInt16 aaWorld; // [x, y, z] world-frame accel sensor measurements

VectorFloat gravity; // [x, y, z] gravity vector

float euler[3]; // [psi, theta, phi] Euler angle container

float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector

int GetPacketLoopCount = 0;

int OuterGetPacketLoopCount = 0;

//RTC/FRAM/MPU6050 status flags

bool bMPU6050Ready = true;

bool dmpReady = false; // set true if DMP init was successful

volatile float global_yawval = 0; //updated by GetIMUHeadingDeg()

const uint16_t MAX_GETPACKET_LOOPS = 100; //10/30/19 added for backup loop exit condition in GetCurrentFIFOPacket()

uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops = MAX_GETPACKET_LOOPS); //prototype here so can define a default param

bool bFirstTime = true;

#pragma endregion MPU6050 Support

const int NAV_UPDATE_INTERVAL_MSEC = 200;

void setup()

{

Serial.begin(115200);

Wire.setClock(100000);

// initialize MPU6050 added 09/03/18

Serial.println(F("Initializing MPU6050 ..."));

mpu.initialize();

// verify connection

Serial.println(F("Testing device connections..."));

Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

Serial.println(F("Initializing DMP..."));

devStatus = mpu.dmpInitialize();

// make sure it worked (returns 0 if successful)

if (devStatus == 0)

{

//12/06/19 no longer needed; cal vals already acquired

// Calibration Time: generate offsets and calibrate our MPU6050

//mpu.CalibrateAccel(6);

//mpu.CalibrateGyro(6);

//Serial.println();

//mpu.PrintActiveOffsets();

// turn on the DMP, now that it's ready

Serial.println(F("Enabling DMP..."));

mpu.setDMPEnabled(true);

// set our DMP Ready flag so the main loop() function knows it's okay to use it

Serial.println(F("DMP ready! Waiting for MPU6050 drift rate to settle..."));

dmpReady = true;

// get expected DMP packet size for later comparison

packetSize = mpu.dmpGetFIFOPacketSize();

bMPU6050Ready = true;

mySerial.printf("\nMPU6050 Ready at %2.2f Sec\n", millis() / 1000.f);

}

else

{

// ERROR!

// 1 = initial memory load failed

// 2 = DMP configuration updates failed

// (if it's going to break, usually the code will be 1)

Serial.print(F("DMP Initialization failed (code "));

Serial.print(devStatus);

Serial.println(F(")"));

bMPU6050Ready = false;

}

sinceLastNavUpdateMsec = 0;

}

void loop()

{

if (sinceLastNavUpdateMsec >= NAV_UPDATE_INTERVAL_MSEC)

{

sinceLastNavUpdateMsec -= NAV_UPDATE_INTERVAL_MSEC;

mpu.testConnection();

mpu.resetFIFO();

for (size_t i = 0; i < 10; i++)

{

int count = mpu.getFIFOCount();

delay(10);

}

This program sets up the connection to the MPU6050 and then once every 200 mSec tests the I2C connection, resets the FIFO, and then repeatedly checks the FIFO count to verify that the MPU6050 is actually doing something.

When I ran Kito’s I2C sniffer program on a Teensy 3.2 (taking care to switch the SCL & SDA lines as Kito’s code has it backwards), I get the following output

Opening port
Port open
-----------------
Legend:
 S=Start
 Sr=Start repeat
 P=stoP
 R=Read
 W=Write
 A=Ack
 N=Nak
-----------------
Addr=0x68,W,N,P
S,Addr=0x68,R,N,P
S,Addr=0x68,W,N,P
S,Addr=0x68,R,N,P
S,Addr=0x68,W,N,P
S,Addr=0x68,R,N,P
S,Addr=0x68,W,N,P
S,Addr=0x68,R,N,P
S,Addr=0x68,W,N,P
S,Addr=0x68,R,N,P
S,Addr=0x68,W,N,P

Opening port

Port open

-----------------

Legend:

S=Start

Sr=Start repeat

P=stoP

R=Read

W=Write

A=Ack

N=Nak

-----------------

Addr=0x68,W,N,P

S,Addr=0x68,R,N,P

S,Addr=0x68,W,N,P

S,Addr=0x68,R,N,P

S,Addr=0x68,W,N,P

S,Addr=0x68,R,N,P

S,Addr=0x68,W,N,P

S,Addr=0x68,R,N,P

S,Addr=0x68,W,N,P

S,Addr=0x68,R,N,P

S,Addr=0x68,W,N,P

which isn’t very useful, when compared to the debug output from Jeff Rowberg’s I2CDev program, as follows:

I2C (0x68) writing 1 bytes to 0x6A...C4. Done.
I2C (0x68) reading 2 bytes from 0x72...0 0. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 A8. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 FC. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...1 18. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...1 34. Done (2 read).
I2C (0x68) reading 1 bytes from 0x75...68. Done (1 read).
I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).
I2C (0x68) writing 1 bytes to 0x6A...C4. Done.
I2C (0x68) reading 2 bytes from 0x72...0 1C. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 A8. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 FC. Done (2 read).

I2C (0x68) writing 1 bytes to 0x6A...C4. Done.

I2C (0x68) reading 2 bytes from 0x72...0 0. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 A8. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 FC. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...1 18. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...1 34. Done (2 read).

I2C (0x68) reading 1 bytes from 0x75...68. Done (1 read).

I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).

I2C (0x68) writing 1 bytes to 0x6A...C4. Done.

I2C (0x68) reading 2 bytes from 0x72...0 1C. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 A8. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 FC. Done (2 read).

As can be seen from Jeff’s output, there is a LOT of data being missed by Kito’s program. It gets the initial sequence right (S,Addr=0x68,W,N,P), but skips the 8-bit data sequence after the ‘W’, and mis-detects the following RESTART as a STOP. The next sequence (S,Addr=0x68,R,N,P) is correct as far as the initial address is concerned, but again omits the 8-bit data value after the ‘R’ direction modifier.

Notwithstanding its problems, Kito’s program, along with this I2C bus specifications document did teach me a LOT about the I2C protocol and how to parse it effectively. In addition, Kito’s program showed me how to use direct port bus reads to bypass the overhead associated with ‘digitalRead()’ calls – nice!

I got lost pretty quickly trying to understand Kito’s programming logic, so I decided I would do what any good researcher does when trying to understand a complex situation – CHEAT!! I modified Kito’s program to simply capture the I2C bus transitions associated with my little test program into a 1024 byte buffer, then stop and print the contents of the buffer out to the serial port. Then I copy/pasted this output into an Excel spreadsheet and wrote a VBA script to parse through the output, line-by-line. By doing it this way, I could easily examine the result of each script change, and step through the script one line at a time, watching the parsing machinery run.

Here’s a partial output from the data capture program:

Buffer full - Printing 1024 byte Contents!
0xc
0x4
0x0
0x8
0xc
0x8
0xc
0x0
0x4
0x8
0xc
0x0
0x4
0x0
0x4
0x0
0x4
0x0
0x4
0x0
0x4
0x8
0x0
0x4
0x0
0x8
0xc
0x8
0xc
0x8
0xc
0x8
0x0
0x4
0x0
0x8
0xc

Buffer full - Printing 1024 byte Contents!

0xc

0x4

0x0

0x8

0xc

0x8

0xc

0x0

0x4

0x8

0xc

0x0

0x4

0x0

0x4

0x0

0x4

0x0

0x4

0x0

0x4

0x8

0x0

0x4

0x0

0x8

0xc

0x8

0xc

0x8

0xc

0x8

0x0

0x4

0x0

0x8

0xc

So then I copy/pasted this into Excel and wrote the following VBA script to parse the data:

Sub Test()
    'Purpose: Parse recorded bytes containing combined I2C SCL/SDA states
    'Inputs: recorded bytes containing combined SCL & SDA states
    'Outputs:  Decoded I2C data
    'Notes:
    '   Each I2C communication proceeds as follows:
    '       A START condition, denoted by SDA & SCL HIGH, followed by SDA LOW, SCL HIGH
    '       A 7-bit device address
    '       A R/W bit
    '       An ACK bit
    '       Data read/write, each data byte consisting of:
    '           8 data bits
    '           ACK/NACK
    '       A Repeated START or STOP
    '   Other than the START/Repeated Start and the STOP conditions, all bit definitions
    '   start with the SCL line LOW, and finish with the SCL line HIGH, as follows:
    '       SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0" or "WRITE" or "ACK"
    '           "WRITE" if it is the bit immediately following the 7 device
    '           address bits
    '           "ACK" if it is the bit immediately following 8 data bits or the
    '           bit immediately following the R/W bit
    '           Otherise it is a "0"
    '       SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1" or "READ" or "NAK"
    '           "READ" if it is the bit immediately following the 7 device
    '           address bits
    '           "NAK" if it is the bit immediately following 8 data bits or the
    '           bit immediately following the R/W bit
    '           Otherise it is a "1"
    '   A special case occurs for a transition from SDA = HIGH/LOW to "0X0" (both LOW).
    '   This means the slave isn't ready for the next bit and has pulled the SCL
    '   line LOW.  Processing has to skip bits until the next 0X0->0X4 or 0X08->0XC
    '   transition occurs to continue

    Dim startrange As Range
    Dim searchrange As Range
    Dim findrange As Range
    Dim datarange As Range
    
    With Worksheets("Sheet1")
        Set startrange = .Range("RawDataColStart")
        Set searchrange = .Range("A:A")
        
        'Find first row with no text in the 'CA Cat' column (column B) command can fail - trap error
        On Error Resume Next
        Set findrange = searchrange.Find("", startrange, xlValues, , xlByRows, xlNext)
        Set datarange = Range(startrange.Address, findrange.Address)
        'OK, now findrange.row is the row number of the first row with "" in the "CA Cat" column (column B)
        Dim datacell As Range
        Dim bitcount As Integer
        Dim startrow As Integer
        Dim startcount As Integer 'needed for repeated start detection
        Dim lastbitrow As Integer 'needed to put the byte value on correct row
        Dim Is7BitAddress As Boolean 'addresses are 7-bit, data is 8-bit
        Dim row As Integer 'needed for byRef sub/function calls
'        Dim IsSTOP As Boolean 'added 12/25/19 for better code readability
        Dim i As Integer 'backup iteration counter
        
        If datarange.Rows.Count > 1 Then
            
'            For row = 1 To datarange.Rows.Count
            row = 1
            While row < datarange.Rows.Count
                If UCase(datarange.Cells(row, 1)) = "0XC" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
                    If startcount = 0 Then
                        datarange.Cells(row + 1, 2) = "START"
                        startcount = startcount + 1 'needed for later repeated start treatment
                    Else
                        datarange.Cells(row + 1, 2) = "RE-START"
                    End If
                    bitcount = 0
                    startrow = row 'need this to tell if bit 9 is 'ACK/NACK' or 'R/W'
                    row = row + 2 'point to next line pair
                    
                    'skip any NOP rows
'                    row = SkipNOPs(row, datarange)
                    Call SkipNOPs(row, datarange)
                    
                    'Get 7-bit address
'                    row = Build7BitAddress(row + 1, datarange) 'point to line following "START" or "RESTART
                    bitcount = Build7BitAddress(row, datarange) 'point to first address line pair
                    
                    If bitcount = 7 Then 'success
                        'Read/Write
                        Call GetReadWrite(row, datarange) 'point to line following last address bit
                        
                        'ACK/NAK
                        Call GetACKNAK(row, datarange)
                        
                        'skip any NOP rows
    '                    row = SkipNOPs(row, datarange) 'points to row after "START/RE-START"
                        Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"
                        
                        '8-bit Data Byte
                        bitcount = Build8BitValue(row, datarange) ' 7-bit address always followed by an 8-bit value/addr
                            
                        If bitcount = 8 Then 'success
                            'ACK/NAK
                            Call GetACKNAK(row, datarange)
                            
                            'skip any NOP rows
                            Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"
                        End If
                            
                        'can have any number of 8-bit-ACK/NAK-SkipNOP cycles
                        While (bitcount = 8 And IsSTOP(row, datarange) = 0 And IsSTART(row, datarange) = 0)
                            
                            '8-bit Data Byte
                            bitcount = Build8BitValue(row, datarange) ' 7-bit address always followed by an 8-bit value/addr
                            
                            If bitcount = 8 Then 'success
                                'ACK/NAK
                                Call GetACKNAK(row, datarange)
                                
                                'skip any NOP rows
                                Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"
                            End If
                        Wend
                  End If
                    
                ElseIf UCase(datarange.Cells(row, 1)) = "0X4" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
                    datarange.Cells(row + 1, 2) = "STOP"
                    bitcount = 0
                    startcount = 0 'a STOP resets repeated start detection counter
'                    row = row + 1 'needed to skip the "0X0" line after STOP detection
                End If
                
                row = row + 2 'move focus to next line pair
                                
                'skip any NOP rows
                Call SkipNOPs(row, datarange)
            Wend
        End If
    End With
End Sub

Function Build8BitDataValueStr(ByVal rownum As Integer) As String
'Inputs:
'   rownum = integer denoting row containing LSB
'Outputs:
'   string containing hexidecimal representation of preceding 8 bit strings
'Plan:
'   start on this row and then every other row going backwards,
'   adding up bit positions to obtain a decimal represntation of the 7-bit value,
'   then convert to a hexidecimal number then convert the number to a string.

    Dim startrow As Integer, bitrow As Integer
    Dim bytedecval As Integer
    
    startrow = rownum
    For bitpos = 0 To 7
        bitrow = startrow - bitpos * 2
'        Debug.Print ("row " & bitrow)
        
        If Cells(bitrow, 2) = "1" Then
                bytedecval = bytedecval + 2 ^ (bitpos)
        End If
    Next bitpos
    
'    Debug.Print ("hex value = " & Hex(bytedecval))
    Build8BitDataValueStr = Hex(bytedecval)
End Function

Function Build7BitAddress(ByRef row As Integer, datarange As Range) As Integer
'Purpose:  build and display 7-bit address
'Inputs:
'   row = line number of first address pair
'   dr = datarange (column containing transition data)
'Outputs:
'   displayed bit & bitnumber values
'   displayed 7-bit address
'   line number of next line pair

    For bitcount = 1 To 7
    
'       SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0"
        If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
            datarange.Cells(row + 1, 2) = "0"
            datarange.Cells(row + 1, 3) = bitcount
            
'       SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1"
        ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
                datarange.Cells(row + 1, 2) = "1"
                datarange.Cells(row + 1, 3) = bitcount
        Else: Exit For
        End If
        row = row + 2 'skip to next bit pair
    Next bitcount
    
    If bitcount = 8 Then
    
        'Now build and display the address string
        Dim AddrStr As String
        AddrStr = Build7BitAddressStr(row - 1)
        datarange.Cells(row - 1, 4) = AddrStr
        
        bitcount = bitcount - 1
    End If

    Build7BitAddress = bitcount 'on success, should be 7

End Function

Function Build7BitAddressStr(ByVal rownum As Integer) As String
'Inputs:
'   rownum = integer denoting row containing LSB
'Outputs:
'   string containing hexidecimal representation of preceding 7 bit strings
'Plan:
'   start on this row and then every other row going backwards,
'   adding up bit positions to obtain a decimal represntation of the 7-bit value,
'   then convert to a hexidecimal number then convert the number to a string.

    Dim startrow As Integer, bitrow As Integer
    Dim bytedecval As Integer
    
'    startrow = rownum - 2 'rownum arg actually points to W/R row
    startrow = rownum
    For bitpos = 0 To 7
        bitrow = startrow - bitpos * 2
'        Debug.Print ("row " & bitrow)
        
        If Cells(bitrow, 2) = "1" Then
            If bitpos = 0 Then
                bytedecval = 1
            Else
                bytedecval = bytedecval + 2 ^ (bitpos)
            End If
        End If
    Next bitpos
    
'    Debug.Print ("hex value = " & Hex(bytedecval))
    Build7BitAddressStr = Hex(bytedecval)
End Function

Function Build8BitValue(ByRef row As Integer, datarange As Range) As Integer
'Purpose:  build & display 8-bit data bits
'Inputs:
'   row = row containing 2nd transition of ACK/NAK pair (points at the ACK/NAK display line)
'   dr = datarange (column containing transition data)
'Outputs:
'   displayed bit & bitnumber values
'   displayed 8-bit value
'   displayed ACK/NAK value
'   row number of second transition value for ACK/NAK pair (points at the ACK/NAK display line)
'Notes:
'   there may be one or more 'NOP' transitions before the first data bit transition pair

    For bitcount = 1 To 8
            
'       SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0"
        If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
            datarange.Cells(row + 1, 2) = "0"
            datarange.Cells(row + 1, 3) = bitcount
            
'       SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1"
        ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
                datarange.Cells(row + 1, 2) = "1"
                datarange.Cells(row + 1, 3) = bitcount
        Else 'oops - something went wrong
            row = row - 2 'back up row counter to start of last good pair
            Exit For
        End If
        row = row + 2 'skip to next bit pair
    Next bitcount
    
    If bitcount = 9 Then '9 here means a full 8-bit byte has been processed
        'Now build and display the address string
        Dim DataValStr As String
        DataValStr = Build8BitDataValueStr(row - 1)
        datarange.Cells(row - 1, 4) = DataValStr
    End If
    
    Build8BitValue = bitcount - 1
End Function

'Function SkipNOPs(ByVal row As Integer, datarange As Range) As Integer
Sub SkipNOPs(ByRef row As Integer, datarange As Range)
    'check for NOP transitions
    While ((UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0X0") _
            Or (UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0X4") _
            Or (UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X8") _
            )
       row = row + 1
    Wend
    
'    SkipNOPs = row
End Sub

Sub GetReadWrite(ByRef row As Integer, datarange As Range)
    'Next line pair is W/R
            
'       SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "WRITE"
    If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
        datarange.Cells(row + 1, 2) = "WRITE"
        
'       SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "READ"
    ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
            datarange.Cells(row + 1, 2) = "READ"
    End If
    
    row = row + 2
    
End Sub

Sub GetACKNAK(ByRef row As Integer, datarange As Range)

    'Next line pair is ACK/NAK

'       SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "ACK"
    If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
        datarange.Cells(row + 1, 2) = "ACK"

'       SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "NAK"
    ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
            datarange.Cells(row + 1, 2) = "NAK"
    End If
    
    row = row + 2
End Sub

Function IsSTOP(ByRef row As Integer, datarange As Range) As Boolean
    If UCase(datarange.Cells(row, 1)) = "0X4" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then
        IsSTOP = True
    Else
        IsSTOP = False
    End If
End Function
Function IsSTART(ByRef row As Integer, datarange As Range) As Boolean
    If UCase(datarange.Cells(row, 1)) = "0XC" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then
        IsSTART = True
    Else
        IsSTART = False
    End If
End Function

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Sub Test()

'Purpose: Parse recorded bytes containing combined I2C SCL/SDA states

'Inputs: recorded bytes containing combined SCL & SDA states

'Outputs: Decoded I2C data

'Notes:

' Each I2C communication proceeds as follows:

' A START condition, denoted by SDA & SCL HIGH, followed by SDA LOW, SCL HIGH

' A 7-bit device address

' A R/W bit

' An ACK bit

' Data read/write, each data byte consisting of:

' 8 data bits

' ACK/NACK

' A Repeated START or STOP

' Other than the START/Repeated Start and the STOP conditions, all bit definitions

' start with the SCL line LOW, and finish with the SCL line HIGH, as follows:

' SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0" or "WRITE" or "ACK"

' "WRITE" if it is the bit immediately following the 7 device

' address bits

' "ACK" if it is the bit immediately following 8 data bits or the

' bit immediately following the R/W bit

' Otherise it is a "0"

' SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1" or "READ" or "NAK"

' "READ" if it is the bit immediately following the 7 device

' address bits

' "NAK" if it is the bit immediately following 8 data bits or the

' bit immediately following the R/W bit

' Otherise it is a "1"

' A special case occurs for a transition from SDA = HIGH/LOW to "0X0" (both LOW).

' This means the slave isn't ready for the next bit and has pulled the SCL

' line LOW. Processing has to skip bits until the next 0X0->0X4 or 0X08->0XC

' transition occurs to continue

Dim startrange As Range

Dim searchrange As Range

Dim findrange As Range

Dim datarange As Range

With Worksheets("Sheet1")

Set startrange = .Range("RawDataColStart")

Set searchrange = .Range("A:A")

'Find first row with no text in the 'CA Cat' column (column B) command can fail - trap error

On Error Resume Next

Set findrange = searchrange.Find("", startrange, xlValues, , xlByRows, xlNext)

Set datarange = Range(startrange.Address, findrange.Address)

'OK, now findrange.row is the row number of the first row with "" in the "CA Cat" column (column B)

Dim datacell As Range

Dim bitcount As Integer

Dim startrow As Integer

Dim startcount As Integer 'needed for repeated start detection

Dim lastbitrow As Integer 'needed to put the byte value on correct row

Dim Is7BitAddress As Boolean 'addresses are 7-bit, data is 8-bit

Dim row As Integer 'needed for byRef sub/function calls

' Dim IsSTOP As Boolean 'added 12/25/19 for better code readability

Dim i As Integer 'backup iteration counter

If datarange.Rows.Count > 1 Then

' For row = 1 To datarange.Rows.Count

row = 1

While row < datarange.Rows.Count

If UCase(datarange.Cells(row, 1)) = "0XC" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

If startcount = 0 Then

datarange.Cells(row + 1, 2) = "START"

startcount = startcount + 1 'needed for later repeated start treatment

Else

datarange.Cells(row + 1, 2) = "RE-START"

End If

bitcount = 0

startrow = row 'need this to tell if bit 9 is 'ACK/NACK' or 'R/W'

row = row + 2 'point to next line pair

'skip any NOP rows

' row = SkipNOPs(row, datarange)

Call SkipNOPs(row, datarange)

'Get 7-bit address

' row = Build7BitAddress(row + 1, datarange) 'point to line following "START" or "RESTART

bitcount = Build7BitAddress(row, datarange) 'point to first address line pair

If bitcount = 7 Then 'success

'Read/Write

Call GetReadWrite(row, datarange) 'point to line following last address bit

'ACK/NAK

Call GetACKNAK(row, datarange)

'skip any NOP rows

' row = SkipNOPs(row, datarange) 'points to row after "START/RE-START"

Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"

'8-bit Data Byte

bitcount = Build8BitValue(row, datarange) ' 7-bit address always followed by an 8-bit value/addr

If bitcount = 8 Then 'success

'ACK/NAK

Call GetACKNAK(row, datarange)

'skip any NOP rows

Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"

End If

'can have any number of 8-bit-ACK/NAK-SkipNOP cycles

While (bitcount = 8 And IsSTOP(row, datarange) = 0 And IsSTART(row, datarange) = 0)

'8-bit Data Byte

bitcount = Build8BitValue(row, datarange) ' 7-bit address always followed by an 8-bit value/addr

If bitcount = 8 Then 'success

'ACK/NAK

Call GetACKNAK(row, datarange)

'skip any NOP rows

Call SkipNOPs(row, datarange) 'points to row after "START/RE-START"

End If

Wend

End If

ElseIf UCase(datarange.Cells(row, 1)) = "0X4" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

datarange.Cells(row + 1, 2) = "STOP"

bitcount = 0

startcount = 0 'a STOP resets repeated start detection counter

' row = row + 1 'needed to skip the "0X0" line after STOP detection

End If

row = row + 2 'move focus to next line pair

'skip any NOP rows

Call SkipNOPs(row, datarange)

Wend

End If

End With

End Sub

Function Build8BitDataValueStr(ByVal rownum As Integer) As String

'Inputs:

' rownum = integer denoting row containing LSB

'Outputs:

' string containing hexidecimal representation of preceding 8 bit strings

'Plan:

' start on this row and then every other row going backwards,

' adding up bit positions to obtain a decimal represntation of the 7-bit value,

' then convert to a hexidecimal number then convert the number to a string.

Dim startrow As Integer, bitrow As Integer

Dim bytedecval As Integer

startrow = rownum

For bitpos = 0 To 7

bitrow = startrow - bitpos * 2

' Debug.Print ("row " & bitrow)

If Cells(bitrow, 2) = "1" Then

bytedecval = bytedecval + 2 ^ (bitpos)

End If

Next bitpos

' Debug.Print ("hex value = " & Hex(bytedecval))

Build8BitDataValueStr = Hex(bytedecval)

End Function

Function Build7BitAddress(ByRef row As Integer, datarange As Range) As Integer

'Purpose: build and display 7-bit address

'Inputs:

' row = line number of first address pair

' dr = datarange (column containing transition data)

'Outputs:

' displayed bit & bitnumber values

' displayed 7-bit address

' line number of next line pair

For bitcount = 1 To 7

' SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0"

If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

datarange.Cells(row + 1, 2) = "0"

datarange.Cells(row + 1, 3) = bitcount

' SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1"

ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

datarange.Cells(row + 1, 2) = "1"

datarange.Cells(row + 1, 3) = bitcount

Else: Exit For

End If

row = row + 2 'skip to next bit pair

Next bitcount

If bitcount = 8 Then

'Now build and display the address string

Dim AddrStr As String

AddrStr = Build7BitAddressStr(row - 1)

datarange.Cells(row - 1, 4) = AddrStr

bitcount = bitcount - 1

End If

Build7BitAddress = bitcount 'on success, should be 7

End Function

Function Build7BitAddressStr(ByVal rownum As Integer) As String

'Inputs:

' rownum = integer denoting row containing LSB

'Outputs:

' string containing hexidecimal representation of preceding 7 bit strings

'Plan:

' start on this row and then every other row going backwards,

' adding up bit positions to obtain a decimal represntation of the 7-bit value,

' then convert to a hexidecimal number then convert the number to a string.

Dim startrow As Integer, bitrow As Integer

Dim bytedecval As Integer

' startrow = rownum - 2 'rownum arg actually points to W/R row

startrow = rownum

For bitpos = 0 To 7

bitrow = startrow - bitpos * 2

' Debug.Print ("row " & bitrow)

If Cells(bitrow, 2) = "1" Then

If bitpos = 0 Then

bytedecval = 1

Else

bytedecval = bytedecval + 2 ^ (bitpos)

End If

Next bitpos

' Debug.Print ("hex value = " & Hex(bytedecval))

Build7BitAddressStr = Hex(bytedecval)

End Function

Function Build8BitValue(ByRef row As Integer, datarange As Range) As Integer

'Purpose: build & display 8-bit data bits

'Inputs:

' row = row containing 2nd transition of ACK/NAK pair (points at the ACK/NAK display line)

' dr = datarange (column containing transition data)

'Outputs:

' displayed bit & bitnumber values

' displayed 8-bit value

' displayed ACK/NAK value

' row number of second transition value for ACK/NAK pair (points at the ACK/NAK display line)

'Notes:

' there may be one or more 'NOP' transitions before the first data bit transition pair

For bitcount = 1 To 8

' SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "0"

If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

datarange.Cells(row + 1, 2) = "0"

datarange.Cells(row + 1, 3) = bitcount

' SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "1"

ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

datarange.Cells(row + 1, 2) = "1"

datarange.Cells(row + 1, 3) = bitcount

Else 'oops - something went wrong

row = row - 2 'back up row counter to start of last good pair

Exit For

End If

row = row + 2 'skip to next bit pair

Next bitcount

If bitcount = 9 Then '9 here means a full 8-bit byte has been processed

'Now build and display the address string

Dim DataValStr As String

DataValStr = Build8BitDataValueStr(row - 1)

datarange.Cells(row - 1, 4) = DataValStr

End If

Build8BitValue = bitcount - 1

End Function

'Function SkipNOPs(ByVal row As Integer, datarange As Range) As Integer

Sub SkipNOPs(ByRef row As Integer, datarange As Range)

'check for NOP transitions

While ((UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0X0") _

Or (UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0X4") _

Or (UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X8") _

)

row = row + 1

Wend

' SkipNOPs = row

End Sub

Sub GetReadWrite(ByRef row As Integer, datarange As Range)

'Next line pair is W/R

' SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "WRITE"

If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

datarange.Cells(row + 1, 2) = "WRITE"

' SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "READ"

ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

datarange.Cells(row + 1, 2) = "READ"

End If

row = row + 2

End Sub

Sub GetACKNAK(ByRef row As Integer, datarange As Range)

'Next line pair is ACK/NAK

' SCL LOW, SDA LOW, followed by SCL HIGH, SDA LOW = "ACK"

If UCase(datarange.Cells(row, 1)) = "0X0" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

datarange.Cells(row + 1, 2) = "ACK"

' SCL LOW, SDA HIGH, followed by SCL HIGH, SDA HIGH = "NAK"

ElseIf UCase(datarange.Cells(row, 1)) = "0X8" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

datarange.Cells(row + 1, 2) = "NAK"

End If

row = row + 2

End Sub

Function IsSTOP(ByRef row As Integer, datarange As Range) As Boolean

If UCase(datarange.Cells(row, 1)) = "0X4" And UCase(datarange.Cells(row + 1, 1)) = "0XC" Then

IsSTOP = True

Else

IsSTOP = False

End If

End Function

Function IsSTART(ByRef row As Integer, datarange As Range) As Boolean

If UCase(datarange.Cells(row, 1)) = "0XC" And UCase(datarange.Cells(row + 1, 1)) = "0X4" Then

IsSTART = True

Else

IsSTART = False

End If

End Function

The above script assumes the data is in column A, starting at A1. A partial output from the program is shown below, showing the first few sequences

0xc			
0x4	START		
0x0			
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x8			
0x0			
0x4	0	1	
0x0			
0x8			
0xc			
0x8			
0xc			
0x8			
0xc			
0x8			
0x0			
0x4			
0x0			
0x8			
0xc			
0x8			
0x0			
0x4			
0x0			
0x8			
0xc			
0x8			
0x0			
0x4			
0x0			
0x4			
0xc			
0x4	RE-START		
0x0			
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x8			
0x0			
0x4			
0x0			
0x8			
0xc			
0x8			
0x0			
0x4			
0x0			
0x4			
0x0			
0x4			
0x0			
0x8			
0xc			
0x8			
0x0			
0x4			
0x0			
0x4			
0x8			
0xc			
0x8			
0xc			
0x0			
0x4			
0x8			
0xc			
0x0			
0x4			
0x0			
0x4			
0x0			
0x4			
0x8			
0xc			
0x8			
0x0			
0x4			
0xc			
0x4	RE-START		
0x0			
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x8			
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x0			
0x4	0	4	
0x8			
0xc	1	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	6A
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x0			
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	C0

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0xc

0x4 START

0x0

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x8

0x0

0x4 0 1

0x0

0x8

0xc

0x8

0xc

0x8

0xc

0x8

0x0

0x4

0x0

0x8

0xc

0x8

0x0

0x4

0x0

0x8

0xc

0x8

0x0

0x4

0x0

0x4

0xc

0x4 RE-START

0x0

0x8

0xc 1 1

0x8

0xc 1 2

0x8

0x0

0x4

0x0

0x8

0xc

0x8

0x0

0x4

0x0

0x4

0x0

0x4

0x0

0x8

0xc

0x8

0x0

0x4

0x0

0x4

0x8

0xc

0x8

0xc

0x0

0x4

0x8

0xc

0x0

0x4

0x0

0x4

0x0

0x4

0x8

0xc

0x8

0x0

0x4

0xc

0x4 RE-START

0x0

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x8

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x0

0x4 0 4

0x8

0xc 1 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 6A

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x0

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 C0

The above output corresponds to this line in the debug output from Jeff Rowberg’s I2Cdev code:

I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).

1	I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).

So, the VBA program is parsing OK-ish, but is missing big chunks, and there are some weird 1 and 2 bit sequences floating around too.

After some more research, I finally figured out that part of the problem is that the I2C protocol allows a slave device to pull the SCL line low unilaterally to temporarily suspend transmissions until the slave device catches up. This causes ‘NOP’ sequences to appear more or less randomly in the data stream. So, I again modified Kito’s program to first capture a 1024 byte data sample, and then parse through the sample, eliminating any NOP sequences. The result is a ‘clean’ data sample. Here’s the modified Kito program

/*
 Name:		MyLA3.ino
 Created:	5/28/2015 11:53:48 AM
 Author:	kito

 Sniffs i2c bus by polling SCL0(pin19)and SDA0(pin18)sda pins.
 Displays i2c commands in easy to read text output.

 //12/20/19 edited by gfp to correct SCL/SDA pin switch
 //See https://i2c.info/ for protocol details

 //12/27/19 re-written to capture a short sample and then edit the 
 //sample to remove any NOP codes

*/
#include <TimerOne.h>

#define SDA_PIN 18
#define SCL_PIN 19

void setup(void)
{
	interrupts();
	pinMode(2, OUTPUT);
	digitalWriteFast(2, LOW);
	pinMode(LED_BUILTIN, OUTPUT);
	pinMode(SDA_PIN, INPUT);
	pinMode(SCL_PIN, INPUT);
	Timer1.initialize(1); // run every mico second
	Timer1.attachInterrupt(capture_data);


	Serial.begin(115200);
	while (!Serial);

	digitalWriteFast(2, LOW);

}

#define RAWSIZE 1024
uint8_t   raw_read_data[RAWSIZE];  // buffer to capture io pin changes
uint8_t   valid_read_data[RAWSIZE];  // buffer to capture valid sequences
uint16_t  write_index = 0;
uint16_t  read_index = 0;
uint8_t   current_portb = 0xFF;
uint8_t   last_portb = 0xFF;

bool bBufferFull = false;

//12/21/19 modified to just capture one buffer load & then stop
void capture_data(void)
{
	last_portb = current_portb;
	current_portb = GPIOB_PDIR & 12; //reads state of SDA (18) & SCL (19) at same time

	if (last_portb != current_portb && !bBufferFull)
	{
		raw_read_data[write_index++] = current_portb;
		digitalWriteFast(2, !digitalReadFast(2));

	}

	if (write_index >= RAWSIZE)
		bBufferFull = true;
}

uint32_t loop_count = 0;
uint8_t data_current = 0;
uint8_t data_previous;

int     i2c_start_count = 0;
int     i2c_index = 0;
uint8_t byte_build = 0;
uint8_t byte_index = 0;

void loop(void)
{
	if (bBufferFull)
	{
		Serial.printf("Buffer full - Printing %d byte Contents!\n", write_index);
		for (size_t i = 0; i < RAWSIZE; i++)
		{
			Serial.printf("0x%x\n", raw_read_data[i]);
		}

		//OK, now go back through the array, excising invalid sequences
		uint rawidx = 0;
		data_previous = raw_read_data[rawidx];
		uint valididx = 0;
		for (rawidx = 1; rawidx < RAWSIZE;)
		{
			data_current = raw_read_data[rawidx];
			bool validpair = 				
				(
				(data_previous == 0xC && data_current == 0x4) //START or RESTART
				|| (data_previous == 0x4 && data_current == 0xC) //STOP
				|| (data_previous == 0x0 && data_current == 0x4) //0 OR ACK
				|| (data_previous == 0x8 && data_current == 0xC) //1 or NAK
				);

			Serial.printf("idx %d: Considering dp = %x, dc = %x: validity = %d\n", 
				rawidx, data_previous, data_current, validpair);
			if (validpair)
			{
				valid_read_data[valididx] = data_previous;
				Serial.printf("Wrote %x into %d, ", valid_read_data[valididx], valididx);
				valididx++; //bump counter to next pair
				valid_read_data[valididx] = data_current;
				Serial.printf("Wrote %x into %d\n", valid_read_data[valididx], valididx);
				valididx++; //pont to next blank entry

				rawidx++;
				data_previous = raw_read_data[rawidx];
				rawidx++;

			}
			else
			{
				data_previous = data_current;
				rawidx++; //only bump 1
			}
		}

		delay(1000);

		Serial.printf("Buffer processed - Printing %d byte Contents of valid_read_data array\n", valididx);
		for (size_t i = 0; i < valididx; i++)
		{
			Serial.printf("0x%x\n", valid_read_data[i]);
		}



		Serial.printf("\n\nDone - Stopping Program!\n");
		while (1)
		{

		}
	}
}

100

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Name: MyLA3.ino

Created: 5/28/2015 11:53:48 AM

Author: kito

Sniffs i2c bus by polling SCL0(pin19)and SDA0(pin18)sda pins.

Displays i2c commands in easy to read text output.

//12/20/19 edited by gfp to correct SCL/SDA pin switch

//See https://i2c.info/ for protocol details

//12/27/19 re-written to capture a short sample and then edit the

//sample to remove any NOP codes

#include <TimerOne.h>

#define SDA_PIN 18

#define SCL_PIN 19

void setup(void)

{

interrupts();

pinMode(2, OUTPUT);

digitalWriteFast(2, LOW);

pinMode(LED_BUILTIN, OUTPUT);

pinMode(SDA_PIN, INPUT);

pinMode(SCL_PIN, INPUT);

Timer1.initialize(1); // run every mico second

Timer1.attachInterrupt(capture_data);

Serial.begin(115200);

while (!Serial);

digitalWriteFast(2, LOW);

}

#define RAWSIZE 1024

uint8_t raw_read_data[RAWSIZE]; // buffer to capture io pin changes

uint8_t valid_read_data[RAWSIZE]; // buffer to capture valid sequences

uint16_t write_index = 0;

uint16_t read_index = 0;

uint8_t current_portb = 0xFF;

uint8_t last_portb = 0xFF;

bool bBufferFull = false;

//12/21/19 modified to just capture one buffer load & then stop

void capture_data(void)

{

last_portb = current_portb;

current_portb = GPIOB_PDIR & 12; //reads state of SDA (18) & SCL (19) at same time

if (last_portb != current_portb && !bBufferFull)

{

raw_read_data[write_index++] = current_portb;

digitalWriteFast(2, !digitalReadFast(2));

}

if (write_index >= RAWSIZE)

bBufferFull = true;

}

uint32_t loop_count = 0;

uint8_t data_current = 0;

uint8_t data_previous;

int i2c_start_count = 0;

int i2c_index = 0;

uint8_t byte_build = 0;

uint8_t byte_index = 0;

void loop(void)

{

if (bBufferFull)

{

Serial.printf("Buffer full - Printing %d byte Contents!\n", write_index);

for (size_t i = 0; i < RAWSIZE; i++)

{

Serial.printf("0x%x\n", raw_read_data[i]);

}

//OK, now go back through the array, excising invalid sequences

uint rawidx = 0;

data_previous = raw_read_data[rawidx];

uint valididx = 0;

for (rawidx = 1; rawidx < RAWSIZE;)

{

data_current = raw_read_data[rawidx];

bool validpair =

(

(data_previous == 0xC && data_current == 0x4) //START or RESTART

|| (data_previous == 0x4 && data_current == 0xC) //STOP

|| (data_previous == 0x0 && data_current == 0x4) //0 OR ACK

|| (data_previous == 0x8 && data_current == 0xC) //1 or NAK

);

Serial.printf("idx %d: Considering dp = %x, dc = %x: validity = %d\n",

rawidx, data_previous, data_current, validpair);

if (validpair)

{

valid_read_data[valididx] = data_previous;

Serial.printf("Wrote %x into %d, ", valid_read_data[valididx], valididx);

valididx++; //bump counter to next pair

valid_read_data[valididx] = data_current;

Serial.printf("Wrote %x into %d\n", valid_read_data[valididx], valididx);

valididx++; //pont to next blank entry

rawidx++;

data_previous = raw_read_data[rawidx];

rawidx++;

}

else

{

data_previous = data_current;

rawidx++; //only bump 1

}

delay(1000);

Serial.printf("Buffer processed - Printing %d byte Contents of valid_read_data array\n", valididx);

for (size_t i = 0; i < valididx; i++)

{

Serial.printf("0x%x\n", valid_read_data[i]);

}

Serial.printf("\n\nDone - Stopping Program!\n");

while (1)

{

}

and a partial output from the run:

Buffer full - Printing 1024 byte Contents!
0xc
0x4
0x0
0x8
0xc
0x8
........
........

idx 1: Considering dp = c, dc = 4: validity = 1
Wrote c into 0, Wrote 4 into 1
idx 3: Considering dp = 0, dc = 8: validity = 0
idx 4: Considering dp = 8, dc = c: validity = 1
Wrote 8 into 2, Wrote c into 3
idx 6: Considering dp = 8, dc = c: validity = 1
Wrote 8 into 4, Wrote c into 5
idx 8: Considering dp = 0, dc = 4: validity = 1
Wrote 0 into 6, Wrote 4 into 7
......
......
......

Buffer processed - Printing 928 byte Contents of valid_read_data array
0xc
0x4
0x8
0xc
0x8
0xc
0x0
0x4
0x8
0xc
0x0
0x4
0x0
0x4
0x0

Buffer full - Printing 1024 byte Contents!

0xc

0x4

0x0

0x8

0xc

0x8

........

idx 1: Considering dp = c, dc = 4: validity = 1

Wrote c into 0, Wrote 4 into 1

idx 3: Considering dp = 0, dc = 8: validity = 0

idx 4: Considering dp = 8, dc = c: validity = 1

Wrote 8 into 2, Wrote c into 3

idx 6: Considering dp = 8, dc = c: validity = 1

Wrote 8 into 4, Wrote c into 5

idx 8: Considering dp = 0, dc = 4: validity = 1

Wrote 0 into 6, Wrote 4 into 7

......

Buffer processed - Printing 928 byte Contents of valid_read_data array

0xc

0x4

0x8

0xc

0x8

0xc

0x0

0x4

0x8

0xc

0x0

0x4

0x0

0x4

0x0

After processing all 1024 transition codes, 96 invalid transitions were removed, resulting in 928 valid I2C transitions.

When this data was copy/pasted into my Excel VBA program, it was able to correctly parse the entire sample correctly, as shown below:

0xc			
0x4	START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x8			
0xc	1	8	75
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x0			
0x4	0	4	
0x8			
0xc	1	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	68
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x0			
0x4	0	4	
0x8			
0xc	1	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	6A
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	C0
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x0			
0x4	0	4	
0x8			
0xc	1	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	6A
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	C4
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x8			
0xc	1	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	1C
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x8			
0xc	1	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	38
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	54
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	70
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x8			
0xc	1	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	8C
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x8			
0xc	1	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	C4
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x8			
0xc	1	7	
0x0			
0x4	0	8	72
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x8			
0xc	READ		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x0			
0x4	0	2	
0x0			
0x4	0	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	0
0x0			
0x4	ACK		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x8			
0xc	1	3	
0x0			
0x4	0	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	
0x0			
0x4	0	8	E0
0x8			
0xc	NAK		
0x0			
0x4	0	1	
0xc			
0x4	RE-START		
0x8			
0xc	1	1	
0x8			
0xc	1	2	
0x0			
0x4	0	3	
0x8			
0xc	1	4	
0x0			
0x4	0	5	
0x0			
0x4	0	6	
0x0			
0x4	0	7	68
0x0			
0x4	WRITE		
0x0			
0x4	ACK		
0x0			
0x4	0	1	
0x8			
0xc	1	2

100

101

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103

104

105

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830

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832

833

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850

851

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915

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920

921

922

923

924

925

926

927

928

0xc

0x4 START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x8

0xc 1 6

0x0

0x4 0 7

0x8

0xc 1 8 75

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x0

0x4 0 4

0x8

0xc 1 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 68

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x0

0x4 0 4

0x8

0xc 1 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 6A

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 C0

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x0

0x4 0 4

0x8

0xc 1 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 6A

0x0

0x4 ACK

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x8

0xc 1 6

0x0

0x4 0 7

0x0

0x4 0 8 C4

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x8

0xc 1 4

0x8

0xc 1 5

0x8

0xc 1 6

0x0

0x4 0 7

0x0

0x4 0 8 1C

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x8

0xc 1 3

0x8

0xc 1 4

0x8

0xc 1 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 38

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x8

0xc 1 6

0x0

0x4 0 7

0x0

0x4 0 8 54

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 70

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x8

0xc 1 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x8

0xc 1 5

0x8

0xc 1 6

0x0

0x4 0 7

0x0

0x4 0 8 8C

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x8

0xc 1 6

0x0

0x4 0 7

0x0

0x4 0 8 C4

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

0x8

0xc 1 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x8

0xc 1 7

0x0

0x4 0 8 72

0x0

0x4 ACK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x8

0xc READ

0x0

0x4 ACK

0x0

0x4 0 1

0x0

0x4 0 2

0x0

0x4 0 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 0

0x0

0x4 ACK

0x8

0xc 1 1

0x8

0xc 1 2

0x8

0xc 1 3

0x0

0x4 0 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7

0x0

0x4 0 8 E0

0x8

0xc NAK

0x0

0x4 0 1

0xc

0x4 RE-START

0x8

0xc 1 1

0x8

0xc 1 2

0x0

0x4 0 3

0x8

0xc 1 4

0x0

0x4 0 5

0x0

0x4 0 6

0x0

0x4 0 7 68

0x0

0x4 WRITE

0x0

0x4 ACK

0x0

0x4 0 1

0x8

0xc 1 2

This corresponds to the following lines from Jeff’s program:

I2C (0x68) reading 1 bytes from 0x75...68. Done (1 read).
I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).
I2C (0x68) writing 1 bytes to 0x6A...C4. Done.
I2C (0x68) reading 2 bytes from 0x72...0 1C. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 C4. Done (2 read).
I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).

I2C (0x68) reading 1 bytes from 0x75...68. Done (1 read).

I2C (0x68) reading 1 bytes from 0x6A...C0. Done (1 read).

I2C (0x68) writing 1 bytes to 0x6A...C4. Done.

I2C (0x68) reading 2 bytes from 0x72...0 1C. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 38. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 54. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 70. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 8C. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 C4. Done (2 read).

I2C (0x68) reading 2 bytes from 0x72...0 E0. Done (2 read).

Although the VBA code correctly parsed all the data and missed nothing, there is still a small ‘fly in the ointment’; there is still an extra ‘0’ bit after every transmission sequence. Instead of

START - Addr - R/W - ACK/NAK - Data - ACK/NAK - RESTART - Addr - R/W -  ACK/NAK - Data - ACK/NAK

1	START - Addr - R/W - ACK/NAK - Data - ACK/NAK - RESTART - Addr - R/W - ACK/NAK - Data - ACK/NAK

we have

START - Addr - R/W - ACK/NAK - Data - ACK/NAK - 0 - RESTART - Addr - R/W -  ACK/NAK - Data - ACK/NAK

1	START - Addr - R/W - ACK/NAK - Data - ACK/NAK - 0 - RESTART - Addr - R/W - ACK/NAK - Data - ACK/NAK

with an extra ‘0’ between the ACK/NAK and the RESTART. This appears in every transmission sequence, so it must be a real part of the I2C protocol, but I haven’t yet found an explanation for it.

In any case, it is clear that the Excel VBA program is correctly parsing the captured sequence, so I should now be able to port it into C++ code for my Teensy I2C sniffer.

Stay tuned!

Frank

Wall-E2 Motor Controller Study Part II

3 Replies

Posted 07 December 2019 (Pearl Harbor Day)

Back in May of this year I posted about different motor driver possibilities for my 2-motor and 4-motor robots, and showed some results for two drivers (an Adafruit Featherwing and an Adafruit DRV8871). However, I got kind of sidetracked after this post when I discovered the RFI/EMI problem with the MPU6050 IMU. At the time, I blamed the RFI/EMI problem on the non-linear nature of the newer drivers, and went back to using the L298N linear driver.

After quite a bit of experimentation and work, it finally turned out that most (if not all) the RFI/EMI problem was the Pololu 20D metal-geared motors themselves, and properly suppressing the noise at the motor terminals with bypass capacitors solved the problem. So I have decided to repeat some of my initial motor driver testing.

Adafruit DRV8871 Single Channel Motor Driver Testing:

I removed the L298N driver I have been using up until now on my 2-motor robot, and replaced it with two DRV8871 Single Channel Motor Drivers. The hookup with the DRV8871’s is actually significantly simpler than the L298N, requiring only two control lines per channel instead of three. After the normal number of errors, I got it running and started some long-term tests with the motors running continuously (with varying speeds and directions) while polling the MPU6050 every 200 mSec for yaw data.

This test ran for over 5 hours without problems, and then the GY-521 (generic MPU6050) module stopped responding to requests for data. This is the second MPU6050 module that has behaved this way – running for an indefinite amount of time and then refusing to respond.

305.48	-56.81	3	158	28	4	1
305.49	-56.87	3	157	28	4	1
305.49	-56.95	3	156	28	4	1
305.49	-56.99	3	155	28	4	1
305.50	-56.93	3	154	28	4	1
305.50	-56.93	3	153	28	3	1
305.50	-56.90	3	152	28	3	1
305.51	-56.90	3	151	28	3	1
Min	Yaw	State	Spd	fifoC	IloopsOloops
305.51	-56.89	3	150	28	3	1
305.51	-56.89	3	149	28	3	1
305.52	-56.87	3	148	28	3	1
305.52	-56.86	3	147	28	3	1
305.52	-56.88	3	146	28	2	1
305.53	-56.91	3	145	28	2	1
MPU6050 and/or I2C failure - resetting Arduino!
max_loops	fifoC	InnerCount	OuterCount
100	        0	100	          4

305.48 -56.81 3 158 28 4 1

305.49 -56.87 3 157 28 4 1

305.49 -56.95 3 156 28 4 1

305.49 -56.99 3 155 28 4 1

305.50 -56.93 3 154 28 4 1

305.50 -56.93 3 153 28 3 1

305.50 -56.90 3 152 28 3 1

305.51 -56.90 3 151 28 3 1

Min Yaw State Spd fifoC IloopsOloops

305.51 -56.89 3 150 28 3 1

305.51 -56.89 3 149 28 3 1

305.52 -56.87 3 148 28 3 1

305.52 -56.86 3 147 28 3 1

305.52 -56.88 3 146 28 2 1

305.53 -56.91 3 145 28 2 1

MPU6050 and/or I2C failure - resetting Arduino!

max_loops fifoC InnerCount OuterCount

100 0 100 4

The good news is, the DRV8871 motor drivers worked flawlessly the entire time, and are efficient enough so the T0-3 size chip container was just barely warm to the touch.

I have run several long-term tests now with the DRV8871 drivers and two different MPU6050 modules, and the longest error-free run has been about 5 hours as shown above. However, I have also had the test terminate in less than 5 minutes, so this is clearly not reliable enough for prime time. Also, adding my 2-stage power supply filter back into the system did not seem to effectively suppress errors, so no I have no clue what is going on.

11 December 2019 Update:

I ran the system overnight with the same test program, except I commented out the motor run commands so the motors themselves did not run. The test ran for over 11 hours and was still running fine when I terminated it. So, the motors definitely have to be running for the problem to occur.

15 December 2019 Update:

Hoping to maybe eliminate a variable, I changed from the UNO controller to a Teensy 3.2. As usual, this ‘small change’ took a LOT more time than I thought it would.

There aren’t any good example programs for interfacing a Teensy 3.x with the MPU6050, especially using the I2CDEV/MPU6050/DMP libraries. I had a huge problem trying to track down compile issues with the I2CDev libraries, but in the end it came down to figuring out a way to get I2CDev to use i2c_t3.h instead of Wire.h. I solved this by copying I2CDev.h/cpp from my Libraries folder to my local project/solution folder, and editing the code to define the I2C implementation as I2CDEV_ARDUINO_WIRE and then replacing “#include <Wire.h>” with “#include <i2c_t3.h> in the appropriate section as shown below. I’m sure there are more elegant ways of doing this (maybe adding a ‘I2CDEV_TEENSY_3.X’ section at the top?)

// -----------------------------------------------------------------------------
// I2C interface implementation setting
// -----------------------------------------------------------------------------
#ifndef I2CDEV_IMPLEMENTATION
#define I2CDEV_IMPLEMENTATION       I2CDEV_ARDUINO_WIRE
//#define I2CDEV_IMPLEMENTATION       I2CDEV_BUILTIN_SBWIRE //09/29/19 gfp enabled this to avoid I2C hangups
//#define I2CDEV_IMPLEMENTATION       I2CDEV_BUILTIN_FASTWIRE
#endif // I2CDEV_IMPLEMENTATION

// comment this out if you are using a non-optimal IDE/implementation setting
// but want the compiler to shut up about it
#define I2CDEV_IMPLEMENTATION_WARNINGS

// -----------------------------------------------------------------------------
// I2C interface implementation options
// -----------------------------------------------------------------------------
#define I2CDEV_ARDUINO_WIRE         1 // Wire object from Arduino
#define I2CDEV_BUILTIN_NBWIRE       2 // Tweaked Wire object from Gene Knight's NBWire project
                                      // ^^^ NBWire implementation is still buggy w/some interrupts!
#define I2CDEV_BUILTIN_FASTWIRE     3 // FastWire object from Francesco Ferrara's project
#define I2CDEV_I2CMASTER_LIBRARY    4 // I2C object from DSSCircuits I2C-Master Library at https://github.com/DSSCircuits/I2C-Master-Library
#define I2CDEV_BUILTIN_SBWIRE	    5 // I2C object from Shuning (Steve) Bian's SBWire Library at https://github.com/freespace/SBWire 

// -----------------------------------------------------------------------------
// Arduino-style "Serial.print" debug constant (uncomment to enable)
// -----------------------------------------------------------------------------
//#define I2CDEV_SERIAL_DEBUG

#ifdef ARDUINO
    #if ARDUINO < 100
        #include "WProgram.h"
    #else
        #include "Arduino.h"
    #endif
    #if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
        //#include <Wire.h>
        #include <i2c_t3.h>
#endif
    #if I2CDEV_IMPLEMENTATION == I2CDEV_I2CMASTER_LIBRARY
        #include <I2C.h>
    #endif
	#if I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_SBWIRE
		#include "SBWire.h"
	#endif
#endif

// -----------------------------------------------------------------------------

// I2C interface implementation setting

// -----------------------------------------------------------------------------

#ifndef I2CDEV_IMPLEMENTATION

#define I2CDEV_IMPLEMENTATION I2CDEV_ARDUINO_WIRE

//#define I2CDEV_IMPLEMENTATION I2CDEV_BUILTIN_SBWIRE //09/29/19 gfp enabled this to avoid I2C hangups

//#define I2CDEV_IMPLEMENTATION I2CDEV_BUILTIN_FASTWIRE

#endif // I2CDEV_IMPLEMENTATION

// comment this out if you are using a non-optimal IDE/implementation setting

// but want the compiler to shut up about it

#define I2CDEV_IMPLEMENTATION_WARNINGS

// -----------------------------------------------------------------------------

// I2C interface implementation options

// -----------------------------------------------------------------------------

#define I2CDEV_ARDUINO_WIRE 1 // Wire object from Arduino

#define I2CDEV_BUILTIN_NBWIRE 2 // Tweaked Wire object from Gene Knight's NBWire project

// ^^^ NBWire implementation is still buggy w/some interrupts!

#define I2CDEV_BUILTIN_FASTWIRE 3 // FastWire object from Francesco Ferrara's project

#define I2CDEV_I2CMASTER_LIBRARY 4 // I2C object from DSSCircuits I2C-Master Library at https://github.com/DSSCircuits/I2C-Master-Library

#define I2CDEV_BUILTIN_SBWIRE 5 // I2C object from Shuning (Steve) Bian's SBWire Library at https://github.com/freespace/SBWire

// -----------------------------------------------------------------------------

// Arduino-style "Serial.print" debug constant (uncomment to enable)

// -----------------------------------------------------------------------------

//#define I2CDEV_SERIAL_DEBUG

#ifdef ARDUINO

#if ARDUINO < 100

#include "WProgram.h"

#else

#include "Arduino.h"

#endif

#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE

//#include <Wire.h>

#include <i2c_t3.h>

#endif

#if I2CDEV_IMPLEMENTATION == I2CDEV_I2CMASTER_LIBRARY

#include <I2C.h>

#endif

#if I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_SBWIRE

#include "SBWire.h"

#endif

After making the above change, the project started compiling OK, and I was able to connect to the MPU6050 and pull off yaw values using the DMP.

The next problem occurred when I tried to run a test program with the Adafruit DRV8871 drivers. The two control lines alternate between being used as digital outputs (for direction control) and analog/PWM outputs (for speed control). Unfortunately, once a Teensy 3.2 line has been written to with ‘analogWrite()’, it can no longer be used as a digital output without first running ‘pinMode([pin],OUTPUT)’ on it. This particular little ‘gotcha’ appears to have been there since around 2016, but got lost in the shuffle as it is still there in the latest TeensyDuino libraries.

After fixing that problem, I was successful in both getting yaw values from the MPU6050 using Jeff’s I2CDev libraries, and in driving my Pololu D20 metal-geared motors via the Adafruit DRV8871 motor driver modules.

After getting everything working, I took the time to fork Jeff Rowberg’s I2CDev library, edit I2CDev.h/cpp appropriately and create a pull request for Jeff. The changes were merged into the Github master distro pretty quickly, so in theory at least, all a new Teensy 3.2 user has to do is grab Jeff’s I2CDevLib stuff and go.

Here’s my Teensy 3.2 program for testing the MPU6050/DMP and the Adafruit DRV8871 motor drivers:

/*
    Name:       Teensy_MPU6050_DMP6_V2.ino
    Created:	12/13/2019 7:18:20 PM
    Author:     FRANKNEWXPS15\Frank
*/

#include "MPU6050_6Axis_MotionApps_V6_12.h"
elapsedMillis 	sinceLastNavUpdateMsec; //added 10/15/18 to replace lastmillisec

MPU6050 mpu;
//MPU6050 mpu(0x69);

//using Adafruit DRV8871 motor drivers
#pragma region MOTOR_PARAMS

#define MOTOR1_IN1 3
#define MOTOR1_IN2 4
#define MOTOR2_IN1 5
#define MOTOR2_IN2 6
//const int INTER_STEP_DELAY_MS = 100;
const int INTER_STEP_DELAY_MS = 10;


enum MotorStates
{
	MOTOR_FWD_INCREASING,
	MOTOR_FWD_DECREASING,
	MOTOR_REV_INCREASING,
	MOTOR_REV_DECREASING
};

enum MotorStates motState = MOTOR_FWD_INCREASING;
const int MOTOR_SPEED_MAX = 255;
const int MOTOR_SPEED_MIN = 0;
int motor_speed = 0;
int pgmloops = 0;

#pragma endregion Motor Parameters


#pragma region MPU6050_SUPPORT
uint8_t mpuIntStatus;   // holds actual interrupt status byte from MPU. Used in Homer's Overflow routine
uint8_t devStatus;      // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize;    // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount;     // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer

						// orientation/motion vars
Quaternion q;           // [w, x, y, z]         quaternion container
VectorInt16 aa;         // [x, y, z]            accel sensor measurements
VectorInt16 aaReal;     // [x, y, z]            gravity-free accel sensor measurements
VectorInt16 aaWorld;    // [x, y, z]            world-frame accel sensor measurements
VectorFloat gravity;    // [x, y, z]            gravity vector
float euler[3];         // [psi, theta, phi]    Euler angle container
float ypr[3];           // [yaw, pitch, roll]   yaw/pitch/roll container and gravity vector
int GetPacketLoopCount = 0;
int OuterGetPacketLoopCount = 0;

//RTC/FRAM/MPU6050 status flags
bool bMPU6050Ready = true;
bool dmpReady = false;  // set true if DMP init was successful
volatile float global_yawval = 0; //updated by GetIMUHeadingDeg()
const uint16_t MAX_GETPACKET_LOOPS = 100; //10/30/19 added for backup loop exit condition in GetCurrentFIFOPacket()
uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops = MAX_GETPACKET_LOOPS); //prototype here so can define a default param
bool bFirstTime = true;
#pragma endregion MPU6050 Support

const int NAV_UPDATE_INTERVAL_MSEC = 200;

void setup()
{
    Serial.begin(115200);
    delay(3000);
    Serial.println("In Setup");

    Wire.begin(I2C_MASTER, 0x00, I2C_PINS_18_19, I2C_PULLUP_EXT, 400000);
    Wire.setDefaultTimeout(200000); // 200ms
    Serial.println("After Wire.begin()");

	// verify connection
	Serial.println(F("Testing device connections..."));
	Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

	Serial.println(F("Initializing DMP..."));
	devStatus = mpu.dmpInitialize();

	// supply your own gyro offsets here, scaled for min sensitivity
	//12/03/19 settings from calibration routines
	mpu.setXGyroOffset(58);
	mpu.setYGyroOffset(20);
	mpu.setZGyroOffset(12);
	mpu.setXAccelOffset(1618);
	mpu.setYAccelOffset(3046);
	mpu.setZAccelOffset(4554);

	// make sure it worked (returns 0 if successful)
	if (devStatus == 0)
	{
		//12/06/19 no longer needed; cal vals already acquired
		//// Calibration Time: generate offsets and calibrate our MPU6050
		//mpu.CalibrateAccel(6); 
		//mpu.CalibrateGyro(6);
		//Serial.println();
		//mpu.PrintActiveOffsets();

		// turn on the DMP, now that it's ready
		Serial.println(F("Enabling DMP..."));
		mpu.setDMPEnabled(true);

		// set our DMP Ready flag so the main loop() function knows it's okay to use it
		Serial.println(F("DMP ready! Waiting for MPU6050 drift rate to settle..."));
		dmpReady = true;

		// get expected DMP packet size for later comparison
		packetSize = mpu.dmpGetFIFOPacketSize();
		bMPU6050Ready = true;
		Serial.printf("\nMPU6050 Ready at %2.2f Sec\n", millis() / 1000.f);
	}
	else
	{
		// ERROR!
		// 1 = initial memory load failed
		// 2 = DMP configuration updates failed
		// (if it's going to break, usually the code will be 1)
		Serial.print(F("DMP Initialization failed (code "));
		Serial.print(devStatus);
		Serial.println(F(")"));

		bMPU6050Ready = false;
	}

	Serial.println("DRV8871 test");

	pinMode(MOTOR1_IN1, OUTPUT);
	pinMode(MOTOR1_IN2, OUTPUT);
	pinMode(MOTOR2_IN1, OUTPUT);
	pinMode(MOTOR2_IN2, OUTPUT);

	//ina219.begin();
	//mySerial.printf("Speed\tVolts\tMAmps\tMWatts\n"); //column headers

	//TCCR2B = (TCCR2B & B11111000) | B00000011; // for PWM frequency of 980.39 Hz on pins 3,11

	sinceLastNavUpdateMsec = 0;
}

void loop()
{
	if (sinceLastNavUpdateMsec >= NAV_UPDATE_INTERVAL_MSEC)
	{
		sinceLastNavUpdateMsec -= NAV_UPDATE_INTERVAL_MSEC;

		bool getYawResult = GetIMUHeadingDeg(); //updates global_yawval if successful
		Serial.printf("%3.2f\t%3.2f\t%d\t%d\t%d\t%d\n", millis() / 60000.0, global_yawval, getYawResult, fifoCount, GetPacketLoopCount, OuterGetPacketLoopCount);

		//Motor speed/dir management
		switch (motState)
		{
		case MOTOR_FWD_INCREASING:
			// ramp up forward
			if (motor_speed == 0)
			{
				//Serial.println("give it a whack to start!");
				analogWrite(MOTOR1_IN1, 128);
				analogWrite(MOTOR2_IN1, 128);
			}
			else
			{
				analogWrite(MOTOR1_IN1, motor_speed);
				analogWrite(MOTOR2_IN1, motor_speed);
			}

			//have to change modes back for digital outputs
			pinMode(MOTOR1_IN2, OUTPUT);
			pinMode(MOTOR2_IN2, OUTPUT);
			digitalWrite(MOTOR1_IN2, LOW);
			digitalWrite(MOTOR2_IN2, LOW);

			motor_speed++;
			if (motor_speed >= MOTOR_SPEED_MAX)
			{
				motState = MOTOR_FWD_DECREASING;
			}
			break;
		case MOTOR_FWD_DECREASING:
			// ramp down forward
			analogWrite(MOTOR1_IN1, motor_speed);
			analogWrite(MOTOR2_IN1, motor_speed);

			//have to change modes back for digital outputs
			pinMode(MOTOR1_IN2, OUTPUT);
			pinMode(MOTOR2_IN2, OUTPUT);
			digitalWrite(MOTOR1_IN2, LOW);
			digitalWrite(MOTOR2_IN2, LOW);

			motor_speed--;

			if (motor_speed <= MOTOR_SPEED_MIN)
			{
				motState = MOTOR_REV_INCREASING;
			}
			break;
		case MOTOR_REV_INCREASING:
			// ramp up reverse
			if (motor_speed == 0)
			{
				//Serial.println("give it a whack to start!");
				analogWrite(MOTOR1_IN2, 128);
				analogWrite(MOTOR2_IN2, 128);
			}
			else
			{
				analogWrite(MOTOR1_IN2, motor_speed);
				analogWrite(MOTOR2_IN2, motor_speed);
			}

			//have to change modes back for digital outputs
			pinMode(MOTOR1_IN1, OUTPUT);
			pinMode(MOTOR2_IN1, OUTPUT);
			digitalWrite(MOTOR1_IN1, LOW);
			digitalWrite(MOTOR2_IN1, LOW);


			motor_speed++;

			if (motor_speed >= MOTOR_SPEED_MAX)
			{
				motState = MOTOR_REV_DECREASING;
			}
			break;
		case MOTOR_REV_DECREASING:
			// ramp down reverse
			analogWrite(MOTOR1_IN2, motor_speed);
			analogWrite(MOTOR2_IN2, motor_speed);

			//have to change modes back for digital outputs
			pinMode(MOTOR1_IN1, OUTPUT);
			pinMode(MOTOR2_IN1, OUTPUT);
			digitalWrite(MOTOR1_IN1, LOW);
			digitalWrite(MOTOR2_IN1, LOW);

			motor_speed--;

			if (motor_speed <= MOTOR_SPEED_MIN)
			{
				motState = MOTOR_FWD_INCREASING; //start over
			}
			break;
		default:
			break;
		}

		pgmloops++;
		if (pgmloops == 1000)
		{
			pgmloops = 0;
		}
	}


}

bool GetIMUHeadingDeg()
{
	//Purpose: Get latest yaw (heading) value from IMU
	//Inputs: None.  This function should only be called after mpu.dmpPacketAvailable() returns TRUE
	//Outputs: 
	//	returns true if successful, otherwise false
	//	global_yawval updated on success
	//Plan:
	//Step1: check for overflow and reset the FIFO if it occurs. In this case, wait for new packet
	//Step2: read all available packets to get to latest data
	//Step3: update global_yawval with latest value
	//Notes:
	//	10/08/19 changed return type to boolean
	//	10/08/19 no longer need mpuIntStatus
	//	10/21/19 completely rewritten to use Homer's algorithm

	bool retval = false;

	int flag = GetCurrentFIFOPacket(fifoBuffer, packetSize, MAX_GETPACKET_LOOPS); //get the latest mpu packet

	if (flag != 0) //0 = error exit, 1 = normal exit, 2 = recovered from an overflow
	{
		// display Euler angles in degrees
		mpu.dmpGetQuaternion(&q, fifoBuffer);
		mpu.dmpGetGravity(&gravity, &q);
		mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);

		//compute the yaw value
		global_yawval = ypr[0] * 180 / M_PI;
		retval = true;
	}

	return retval;
}

uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops)
{
	max_loops = max(10, max_loops); //added 12/04/19 to ensure we loop at least 10 times. This really IS a hard-coded number!
	fifoCount = mpu.getFIFOCount();
	GetPacketLoopCount = 0;

	//11/10/19 I have seen this fail with fifoC > 28 on occasion, so now I loop max three times
	OuterGetPacketLoopCount = 0;
	while (fifoCount != packetSize && OuterGetPacketLoopCount <= 3)
	{
		mpu.resetFIFO();
		delay(1);

		fifoCount = mpu.getFIFOCount();
		GetPacketLoopCount = 0;

		while (fifoCount < packetSize && GetPacketLoopCount < max_loops)
		{
			GetPacketLoopCount++;
			fifoCount = mpu.getFIFOCount();
			delay(2);
		}

		//if we get to here, there should be exactly one packet in the FIFO
		OuterGetPacketLoopCount++;
	}

	if (OuterGetPacketLoopCount < 3)
	{
		mpu.getFIFOBytes(data, packetSize);
		return 1;
	}

	return 0; //failed to get a good packet
}

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Name: Teensy_MPU6050_DMP6_V2.ino

Created: 12/13/2019 7:18:20 PM

Author: FRANKNEWXPS15\Frank

#include "MPU6050_6Axis_MotionApps_V6_12.h"

elapsedMillis sinceLastNavUpdateMsec; //added 10/15/18 to replace lastmillisec

MPU6050 mpu;

//MPU6050 mpu(0x69);

//using Adafruit DRV8871 motor drivers

#pragma region MOTOR_PARAMS

#define MOTOR1_IN1 3

#define MOTOR1_IN2 4

#define MOTOR2_IN1 5

#define MOTOR2_IN2 6

//const int INTER_STEP_DELAY_MS = 100;

const int INTER_STEP_DELAY_MS = 10;

enum MotorStates

{

MOTOR_FWD_INCREASING,

MOTOR_FWD_DECREASING,

MOTOR_REV_INCREASING,

MOTOR_REV_DECREASING

};

enum MotorStates motState = MOTOR_FWD_INCREASING;

const int MOTOR_SPEED_MAX = 255;

const int MOTOR_SPEED_MIN = 0;

int motor_speed = 0;

int pgmloops = 0;

#pragma endregion Motor Parameters

#pragma region MPU6050_SUPPORT

uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU. Used in Homer's Overflow routine

uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)

uint16_t packetSize; // expected DMP packet size (default is 42 bytes)

uint16_t fifoCount; // count of all bytes currently in FIFO

uint8_t fifoBuffer[64]; // FIFO storage buffer

// orientation/motion vars

Quaternion q; // [w, x, y, z] quaternion container

VectorInt16 aa; // [x, y, z] accel sensor measurements

VectorInt16 aaReal; // [x, y, z] gravity-free accel sensor measurements

VectorInt16 aaWorld; // [x, y, z] world-frame accel sensor measurements

VectorFloat gravity; // [x, y, z] gravity vector

float euler[3]; // [psi, theta, phi] Euler angle container

float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector

int GetPacketLoopCount = 0;

int OuterGetPacketLoopCount = 0;

//RTC/FRAM/MPU6050 status flags

bool bMPU6050Ready = true;

bool dmpReady = false; // set true if DMP init was successful

volatile float global_yawval = 0; //updated by GetIMUHeadingDeg()

const uint16_t MAX_GETPACKET_LOOPS = 100; //10/30/19 added for backup loop exit condition in GetCurrentFIFOPacket()

uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops = MAX_GETPACKET_LOOPS); //prototype here so can define a default param

bool bFirstTime = true;

#pragma endregion MPU6050 Support

const int NAV_UPDATE_INTERVAL_MSEC = 200;

void setup()

{

Serial.begin(115200);

delay(3000);

Serial.println("In Setup");

Wire.begin(I2C_MASTER, 0x00, I2C_PINS_18_19, I2C_PULLUP_EXT, 400000);

Wire.setDefaultTimeout(200000); // 200ms

Serial.println("After Wire.begin()");

// verify connection

Serial.println(F("Testing device connections..."));

Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

Serial.println(F("Initializing DMP..."));

devStatus = mpu.dmpInitialize();

// supply your own gyro offsets here, scaled for min sensitivity

//12/03/19 settings from calibration routines

mpu.setXGyroOffset(58);

mpu.setYGyroOffset(20);

mpu.setZGyroOffset(12);

mpu.setXAccelOffset(1618);

mpu.setYAccelOffset(3046);

mpu.setZAccelOffset(4554);

// make sure it worked (returns 0 if successful)

if (devStatus == 0)

{

//12/06/19 no longer needed; cal vals already acquired

//// Calibration Time: generate offsets and calibrate our MPU6050

//mpu.CalibrateAccel(6);

//mpu.CalibrateGyro(6);

//Serial.println();

//mpu.PrintActiveOffsets();

// turn on the DMP, now that it's ready

Serial.println(F("Enabling DMP..."));

mpu.setDMPEnabled(true);

// set our DMP Ready flag so the main loop() function knows it's okay to use it

Serial.println(F("DMP ready! Waiting for MPU6050 drift rate to settle..."));

dmpReady = true;

// get expected DMP packet size for later comparison

packetSize = mpu.dmpGetFIFOPacketSize();

bMPU6050Ready = true;

Serial.printf("\nMPU6050 Ready at %2.2f Sec\n", millis() / 1000.f);

}

else

{

// ERROR!

// 1 = initial memory load failed

// 2 = DMP configuration updates failed

// (if it's going to break, usually the code will be 1)

Serial.print(F("DMP Initialization failed (code "));

Serial.print(devStatus);

Serial.println(F(")"));

bMPU6050Ready = false;

}

Serial.println("DRV8871 test");

pinMode(MOTOR1_IN1, OUTPUT);

pinMode(MOTOR1_IN2, OUTPUT);

pinMode(MOTOR2_IN1, OUTPUT);

pinMode(MOTOR2_IN2, OUTPUT);

//ina219.begin();

//mySerial.printf("Speed\tVolts\tMAmps\tMWatts\n"); //column headers

//TCCR2B = (TCCR2B & B11111000) | B00000011; // for PWM frequency of 980.39 Hz on pins 3,11

sinceLastNavUpdateMsec = 0;

}

void loop()

{

if (sinceLastNavUpdateMsec >= NAV_UPDATE_INTERVAL_MSEC)

{

sinceLastNavUpdateMsec -= NAV_UPDATE_INTERVAL_MSEC;

bool getYawResult = GetIMUHeadingDeg(); //updates global_yawval if successful

Serial.printf("%3.2f\t%3.2f\t%d\t%d\t%d\t%d\n", millis() / 60000.0, global_yawval, getYawResult, fifoCount, GetPacketLoopCount, OuterGetPacketLoopCount);

//Motor speed/dir management

switch (motState)

{

case MOTOR_FWD_INCREASING:

// ramp up forward

if (motor_speed == 0)

{

//Serial.println("give it a whack to start!");

analogWrite(MOTOR1_IN1, 128);

analogWrite(MOTOR2_IN1, 128);

}

else

{

analogWrite(MOTOR1_IN1, motor_speed);

analogWrite(MOTOR2_IN1, motor_speed);

}

//have to change modes back for digital outputs

pinMode(MOTOR1_IN2, OUTPUT);

pinMode(MOTOR2_IN2, OUTPUT);

digitalWrite(MOTOR1_IN2, LOW);

digitalWrite(MOTOR2_IN2, LOW);

motor_speed++;

if (motor_speed >= MOTOR_SPEED_MAX)

{

motState = MOTOR_FWD_DECREASING;

}

break;

case MOTOR_FWD_DECREASING:

// ramp down forward

analogWrite(MOTOR1_IN1, motor_speed);

analogWrite(MOTOR2_IN1, motor_speed);

//have to change modes back for digital outputs

pinMode(MOTOR1_IN2, OUTPUT);

pinMode(MOTOR2_IN2, OUTPUT);

digitalWrite(MOTOR1_IN2, LOW);

digitalWrite(MOTOR2_IN2, LOW);

motor_speed--;

if (motor_speed <= MOTOR_SPEED_MIN)

{

motState = MOTOR_REV_INCREASING;

}

break;

case MOTOR_REV_INCREASING:

// ramp up reverse

if (motor_speed == 0)

{

//Serial.println("give it a whack to start!");

analogWrite(MOTOR1_IN2, 128);

analogWrite(MOTOR2_IN2, 128);

}

else

{

analogWrite(MOTOR1_IN2, motor_speed);

analogWrite(MOTOR2_IN2, motor_speed);

}

//have to change modes back for digital outputs

pinMode(MOTOR1_IN1, OUTPUT);

pinMode(MOTOR2_IN1, OUTPUT);

digitalWrite(MOTOR1_IN1, LOW);

digitalWrite(MOTOR2_IN1, LOW);

motor_speed++;

if (motor_speed >= MOTOR_SPEED_MAX)

{

motState = MOTOR_REV_DECREASING;

}

break;

case MOTOR_REV_DECREASING:

// ramp down reverse

analogWrite(MOTOR1_IN2, motor_speed);

analogWrite(MOTOR2_IN2, motor_speed);

//have to change modes back for digital outputs

pinMode(MOTOR1_IN1, OUTPUT);

pinMode(MOTOR2_IN1, OUTPUT);

digitalWrite(MOTOR1_IN1, LOW);

digitalWrite(MOTOR2_IN1, LOW);

motor_speed--;

if (motor_speed <= MOTOR_SPEED_MIN)

{

motState = MOTOR_FWD_INCREASING; //start over

}

break;

default:

break;

}

pgmloops++;

if (pgmloops == 1000)

{

pgmloops = 0;

}

bool GetIMUHeadingDeg()

{

//Purpose: Get latest yaw (heading) value from IMU

//Inputs: None. This function should only be called after mpu.dmpPacketAvailable() returns TRUE

//Outputs:

// returns true if successful, otherwise false

// global_yawval updated on success

//Plan:

//Step1: check for overflow and reset the FIFO if it occurs. In this case, wait for new packet

//Step2: read all available packets to get to latest data

//Step3: update global_yawval with latest value

//Notes:

// 10/08/19 changed return type to boolean

// 10/08/19 no longer need mpuIntStatus

// 10/21/19 completely rewritten to use Homer's algorithm

bool retval = false;

int flag = GetCurrentFIFOPacket(fifoBuffer, packetSize, MAX_GETPACKET_LOOPS); //get the latest mpu packet

if (flag != 0) //0 = error exit, 1 = normal exit, 2 = recovered from an overflow

{

// display Euler angles in degrees

mpu.dmpGetQuaternion(&q, fifoBuffer);

mpu.dmpGetGravity(&gravity, &q);

mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);

//compute the yaw value

global_yawval = ypr[0] * 180 / M_PI;

retval = true;

}

return retval;

}

uint8_t GetCurrentFIFOPacket(uint8_t* data, uint8_t length, uint16_t max_loops)

{

max_loops = max(10, max_loops); //added 12/04/19 to ensure we loop at least 10 times. This really IS a hard-coded number!

fifoCount = mpu.getFIFOCount();

GetPacketLoopCount = 0;

//11/10/19 I have seen this fail with fifoC > 28 on occasion, so now I loop max three times

OuterGetPacketLoopCount = 0;

while (fifoCount != packetSize && OuterGetPacketLoopCount <= 3)

{

mpu.resetFIFO();

delay(1);

fifoCount = mpu.getFIFOCount();

GetPacketLoopCount = 0;

while (fifoCount < packetSize && GetPacketLoopCount < max_loops)

{

GetPacketLoopCount++;

fifoCount = mpu.getFIFOCount();

delay(2);

}

//if we get to here, there should be exactly one packet in the FIFO

OuterGetPacketLoopCount++;

}

if (OuterGetPacketLoopCount < 3)

{

mpu.getFIFOBytes(data, packetSize);

return 1;

}

return 0; //failed to get a good packet

}

Back to the future with Wall-E2. Wall-following Part VII

3 Replies

Posted 06 December 2019

Back in August of this year (4 months ago!) I demonstrated successful wall tracking at an arbitrary offset distance using heading information from a MPU6050 IMU using my little 2-motor robot. At the time (silly me) I thought the next step was to integrate this new capability back into my larger 4-motor robot and let it loose into the ‘wild’ (my house). Unfortunately the EMI/RFI problem that I thought I had solved reared its ugly head again, and sent all my beautiful plans right into the crapper :-(.

So, I have spent the last four months once again tracking down and eliminating the issue (really for sure this time – honest!). As it turned out, the solution was pretty simple, and one that Pololu, the supplier of the metal-geared motors I am using had already described in some detail in this post. Along the way I learned a lot, and had a lot of fun, but to quote Abraham Lincoln “I feel like the man who was tarred and feathered and ridden out of town on a rail. To the man who asked him how he liked it, he said: ‘If it wasn’t for the honor of the thing, I’d rather walk.”

In any case, the MPU6050 IMU on my little 2-motor robot with metal-geared motors is now happily churning out yaw values on a polled basis (no interrupt required, thank you!), and I’m back in business with angle-enhanced wall tracking. Once I got everything working again, I ran some tests on my ‘local field test site’ (AKA my office) to verify that the algorithm still worked and I was still getting good tracking behavior. I have included some Excel plots and a short video showing the results.

Stay tuned,

Frank

Integrating Heading-based Wall Tracking into Wall-E2

Current Algorithm:

Every MIN_PING_INTERVAL_MSEC millisec Wall-E2 measures left/right/forward distances, and then calls ‘GetOpMode()’ to determine its current operating mode. The currently defined modes are:

MODE_NONE: (0) default case
MODE_CHARGING (1): connected to the charger and not finished
MODE_IRHOMING (2): coded IR signal from a charger has been detected
MODE_WALLFOLLOW (3): trying to run parallel to a wall
MODE_DEADBATTERY (4): battery exhausted

The MODE_WALLFOLLOW operational mode is returned from GetOpMode() when none of the other modes are active – in other words it is the real ‘default mode’. The MODE_WALLFOLLOW mode has three distinct sub-modes;

- TRACKING_LEFT (1): actively tracking the left wall
- TRACKING_RIGHT (2): actively tracking the right wall
- TRACKING_NEITHER (3): not tracking either wall (both distances > 200cm)

TRACKING_LEFT & TRACKING_RIGHT are identical for purposes of heading-based wall tracking, and the TRACKING_NEITHER case isn’t relevant, so we just have to come up with a way of integrating heading-based tracking into either the LEFT or RIGHT case. The TRACKING_LEFT case block is shown below:

			case TRACKING_LEFT:
			#pragma region TRACKLEFT
				trackstr = "Left"; //used for telemetry printouts

				//Bkp & Rot Right = Tracking Left && (Near || Stuck)
				if (frontdistval <= MIN_OBS_DIST_CM || IsStuck(frontvar))
				{
					Serial.println("---- Backup & Turn to the Right");

					//09/19/18 bugfix - 1st param is 'nearest wall', not 'turn direction'
					//BackupAndTurn(false, MOTOR_SPEED_HALF); //backup and turn 90 deg right //c/o 02/23/17 for IR Track debug
					BackupAndTurn(true, MOTOR_SPEED_HALF); //backup and turn 90 deg right //c/o 02/23/17 for IR Track debug

					//go back to normal tracking mode after B&T completes
					NavCase = NAV_WALLTRK;
				}

				//Step-turn Right = Tracking Left && Step && !Stuck
				//this section *starts* the step-turn.  It is terminated as soon as frontdistval exits step-turn window
				else if (frontdistval > MIN_OBS_DIST_CM && frontdistval <= STEPTURN_DIST_CM)
				{
					//if we aren't already in Step-turn mode, start it.  Otherwise, skip
					if (NavCase != NAV_STEPTURN)
					{
						Serial.println("---- Starting Stepturn to the Right");
						NavCase = NAV_STEPTURN;
						leftspeednum = MOTOR_SPEED_MAX;
						rightspeednum = MOTOR_SPEED_LOW;
						MoveAhead(leftspeednum, rightspeednum); 
					}
				}

				//Wall-tracking Left = Tracking Left && Far away from obstacles
				else if (frontdistval > STEPTURN_DIST_CM)
				{
					if (NavCase == NAV_STEPTURN)
					{
						mySerial.printf("Exiting Step-turn to the right\n");
					}

					NavCase = NAV_WALLTRK;
					UpdateWallFollowMotorspeeds(leftdistval, rightdistval, leftspeednum, rightspeednum);
					MoveAhead(leftspeednum, rightspeednum); 
				}

				PrintWallFollowTelemetry(frontvar); //added 04/15/19
			#pragma endregion Tracking Left Wall Case
				break;

case TRACKING_LEFT:

#pragma region TRACKLEFT

trackstr = "Left"; //used for telemetry printouts

//Bkp & Rot Right = Tracking Left && (Near || Stuck)

if (frontdistval <= MIN_OBS_DIST_CM || IsStuck(frontvar))

{

Serial.println("---- Backup & Turn to the Right");

//09/19/18 bugfix - 1st param is 'nearest wall', not 'turn direction'

//BackupAndTurn(false, MOTOR_SPEED_HALF); //backup and turn 90 deg right //c/o 02/23/17 for IR Track debug

BackupAndTurn(true, MOTOR_SPEED_HALF); //backup and turn 90 deg right //c/o 02/23/17 for IR Track debug

//go back to normal tracking mode after B&T completes

NavCase = NAV_WALLTRK;

}

//Step-turn Right = Tracking Left && Step && !Stuck

//this section *starts* the step-turn. It is terminated as soon as frontdistval exits step-turn window

else if (frontdistval > MIN_OBS_DIST_CM && frontdistval <= STEPTURN_DIST_CM)

{

//if we aren't already in Step-turn mode, start it. Otherwise, skip

if (NavCase != NAV_STEPTURN)

{

Serial.println("---- Starting Stepturn to the Right");

NavCase = NAV_STEPTURN;

leftspeednum = MOTOR_SPEED_MAX;

rightspeednum = MOTOR_SPEED_LOW;

MoveAhead(leftspeednum, rightspeednum);

}

//Wall-tracking Left = Tracking Left && Far away from obstacles

else if (frontdistval > STEPTURN_DIST_CM)

{

if (NavCase == NAV_STEPTURN)

{

mySerial.printf("Exiting Step-turn to the right\n");

}

NavCase = NAV_WALLTRK;

UpdateWallFollowMotorspeeds(leftdistval, rightdistval, leftspeednum, rightspeednum);

MoveAhead(leftspeednum, rightspeednum);

}

PrintWallFollowTelemetry(frontvar); //added 04/15/19

#pragma endregion Tracking Left Wall Case

break;

The first thing that happens is a check for an obstacle within the MIN_OBS_DIST_CM or the ‘stuck’ condition (determined via a call to ‘IsStuck()’). If this test passes, a check is made for an obstacle that is farther away than MIN_OBS_DIST_CM but closer than STEPTURN_DIST_CM, so a gradual ‘step-turn’ can be made to negotiate an upcoming corner. If that check too fails, then the robot is assumed to be tracking the left wall, safely far from any oncoming obstacles. In this case, a new set of motor speeds is computed using a PID setup to keep the left PING distance constant – no consideration is given for whether or not the PING distance is appropriate – just that it is either greater or less than the one measured in the last pass.

So, the thing we want to change is the way the robot responds to PING distances to the left wall. We want the robot to acquire and maintain a selected standoff distance from the wall being tracked (the LEFT wall in this case). Pretty much by definition, this requires two distinct activities – the first to acquire the selected standoff distance, and the second to maintain that distance for the duration of the wall-tracking activity. So now we have three state variables for wall tracking, and only the last one (ACQUIRE/MAINTAIN) is new

TRACKING_LEFT/RIGHT
- NAV_WALLTRK (as opposed to NAV_STEPTURN)
  - PHASE_ACQUIREDIST/PHASE_MAINTAINDIST

In the PHASE_ACQUIREDIST phase, a heading change of up to 20 deg is made in the appropriate direction to move toward the selected offset distance. The situation is then monitored in subsequent loop passes to determine if a larger or small heading cut is required. When the robot gets close to the desired distance, all the added heading offset is removed and the robot enters the PHASE_MAINTAINDIST phase. In this phase, small(er) ping distance variations cause larg(er) heading changes, resulting in a sawtooth pattern about the selected distance.