Author Archives: paynterf

Better Battery Charging for Wall-E2

Posted 08 February 2019,

After recovering from my bout with #include file hell, I’m back to working on Wall-E2, my autonomous wall-following robot. In a previous post I described the integration of the TP5100 charger module into Wall-E2’s system, but I have lately discovered that the TP5100 end-of-charge (EOC) detection scheme isn’t very reliable in my application. The TP5100 uses a current threshold to determine EOC, which works fine in a normal application where the battery pack isn’t simultaneously supplying current to the load, but in my application, Wall-E2 stays active and alert while it’s docked at it’s feeding station; it has to, in order to be able to respond to the EOC signal and detach itself. So, the current going through the TP5100 never goes below the idling current for Wall-E2, which is on the order of 300mA or so. This is enough to keep the charging current above the TP5100 EOC threshold, and so Wall-E2 hangs on to the charging station forever – not what I had in mind!

Life would be good if I somehow measure Wall-E2’s idling current while on charge and the total charging current. Then I could subtract the two values to get the excess current, i.e. the current going into the battery but not coming out – the current actually going into increasing the battery charge level. When this current falls below an appropriate threshold, then charging could be terminated. This scenario is complicated by the need to measure the current on the high side of the charging circuit and of the +Vbatt supply to the rest of the system.

Well, as it turns out, Adafruit (and I’m sure others) makes a high-side current sensor just for this purpose, based on the 1NA219 and INA169 chips. The INA219 module reports current via an I2C connection, while the 1NA169 module provides a open-emitter current source proportional to the current through an onboard 0.1Ω resistor (see this data sheet for details). My plan is to use two of these modules; one at the charging circuit input, and a second one at the 8.4V +VBatt supply from the battery to the rest of the system. Since Wall-E2 stays awake during charging, it should be simple to monitor both currents and decide when charging is complete (or complete enough, anyway). As a bonus, I should be able to extend the life of Wall-E2’s battery pack by terminating the charge at less than 100% capacity. See this very informative post by François Boucher for the details.

03 March 2019 Update:

After the usual number of mistakes and setbacks, I think I have the dual current sensor feature working, and now WallE-2 charges by monitoring both the battery voltage and the actual charging current (total current measured at the charging connector minus the run current measured on WallE-2’s main power line). As a final test, I discharged the main battery pack at about 1A for about 1 hour, and then charged it again using the two-current method. As shown in the Excel plots below, Charging terminated when the actual battery charging current fell below 50mA.

Complete charge cycle, after discharging at approx 1A for approx 1 Hr

Last 20 minutes or so of charge operation, showing detail of end-of-charge behavior

two 1NA169 high-side current sensors mounted in the battery/motor compartment. Note the 3D-printed mounting plates.

Here is a showing the installation of the two 1NA169 sensor modules in WallE-2’s battery compartment. The one on the left measures running current, and the one on the right measures total current (charging + running).

The following figure shows the system schematic for WallE-2, with the two new 1NA169 sensors highlighted

System schematic with locations of new current sensors highlighted

Now that I have the current sensors and the new charge algorithm working, it’s time to go back an take another look at the charge/discharge characteristics of the Panasonic 18650B cells I’m using to see if I can extend their life with a more intelligent charge/discharge scheme. The following plot shows the charge characteristics for this cell.

Charge plot for the Panasonic 18650B LiPo cell

As noted by François Boucher, the red line above is the total energy returned to the battery during charge. As he notes, the battery acquires about 90% of its total capacity in the first 105 minutes of the charge period, when charged at 0.5C at 25C. My battery pack is a 2-cell parallel x 2-cell series stack, and currently I’m charging to a 50mA cutoff. According to Boucher, this is way too low – I’m charging to almost 100% capacity and thereby limiting the cycle life of the battery pack. Looking at the end-of-charge detail plot above (repeated below), I should probably use a charge current threshold of around 500mA charging current (250mA per cell in the parallel stack) for about 90% capacity charge.

End-of-charge detail with approximate 90% charge current highlighted

On the discharge side, Panasonic’s Discharge Characteristics plot below shows a discharge down to 2.50V/cell. WallE-2’s typical current drain is about 1A or about 0.3 – 0.5C, and the cutoff I’m using is 3.0V cell. From the plot, this gives about 3150mAH of the approximately 3300mAH available at 0.5C, or about 95%. So, it looks like I should raise the discharge cutoff voltage to about 3.2V or about 3000mAH of the 3300mAH available, or about 90%.

Conclusion:

So revisiting WallE-2’s battery management seems to have paid off; I now have much better visibility into and control over charge/discharge of the 18650B battery pack, and at least some expectation that I can use WallE-2’s new found battery super powers for good rather than evil ;-).

Stay tuned!

Frank

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

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Posted 09 February 2019

A long time ago in a galaxy far, far away, I set up a control algorithm for my autonomous wall-following robot Wall-E2. After a lot of tuning, I wound up with basically a bang-bang system using a motor speed step function of about 50, where the full range of motor speeds is 0-255. This works, but as you can see in the following chart & Excel diagram, it’s pretty clunky. The algorithm is shown below, along with an Excel chart of motor speeds taken during a hallway run, and a video of the run.

for left wall tracking

leftspeednum = prevleftspdnum - MOTOR_SPEED_ADJ_FACTOR * (leftdistval - prevleftdistval);
rightspeednum = prevrightspdnum + MOTOR_SPEED_ADJ_FACTOR * (leftdistval - prevleftdistval);

1 2	leftspeednum = prevleftspdnum - MOTOR_SPEED_ADJ_FACTOR * (leftdistval - prevleftdistval); rightspeednum = prevrightspdnum + MOTOR_SPEED_ADJ_FACTOR * (leftdistval - prevleftdistval);

for right wall tracking

leftspeednum = prevleftspdnum + MOTOR_SPEED_ADJ_FACTOR * (rightdistval - prevrightdistval);
rightspeednum = prevrightspdnum - MOTOR_SPEED_ADJ_FACTOR * (rightdistval - prevrightdistval);

1 2	leftspeednum = prevleftspdnum + MOTOR_SPEED_ADJ_FACTOR * (rightdistval - prevrightdistval); rightspeednum = prevrightspdnum - MOTOR_SPEED_ADJ_FACTOR * (rightdistval - prevrightdistval);

Run 1, using homebrew algorithm

Note the row of LEDs on the rear. They display (very roughly) the turn direction and rate.

Since the time I set this up, I started using a PID algorithm for the code that homes the robot in on its charging station using a modulated IR beam, and it seems to work pretty well with a PID value of (Kp,Ki,Kd) = (200,0,0). I’d like to use the knowledge gained for the IR homing subsystem to make Wall-E2 a bit more sophisticated and smooth during wall-following operations (which, after all, will be what Wall-E2 is doing most of the time).

In past work, I have not bothered to set a fixed distance from the wall being followed; I was just happy that Wall-E2 was following the wall at all, much less at a precise distance. Besides, I really didn’t know if having a preferred distance was a good idea. However, with the experience gained so far, I now believe a 20-30 cm offset would probably work very well in our home.

So, my plan is to re-purpose the PID object used for IR homing whenever it isn’t actually in the IR homing mode, but with the PID values appropriate for wall-following rather than beam-riding.

PID Parameters:

For the beam-riding application I used a setpoint of zero, meaning the algorithm adjusts the control value (motor speed adjustment value) to drive the input value (offset from IR beam center) to zero. This works very nicely as can be seen in the videos. However, for the wall-following application I am going to use a setpoint of about 20-30cm, so that the algorithm will (hopefully) drive the motors to achieve this offset. The Kp, Ki, & Kd values will be determined by experimentation.

13 February 2019 Update:

I got the PID controller working with a target offset of 25cm and Kp,Ki,Kd = 2,0,0 and ran some tests in my hallway. In the first test I started with Wall-E2 approximately 25cm away from the wall. As can be seen in the following video, this worked quite well, and I thought “I’m a genius!” Then I ran another test with Wall-E2 starting about 50cm away from the wall, and as can be seen in the second video, Wall-E2 promptly dived nose-first right into the wall, and I thought “I’m an idiot!”

The problem, of course, is the PID algorithm correctly turns Wall-E2 toward the wall to reduce the offset to the target value, but in doing so it changes the orientation of the ping sensor with respect to the wall, and the measured distance goes up instead of down. The PID response is to turn Wall-E2 more, making the problem even worse, ending with Wall-E3 colliding nose-first with the wall it’s supposed to be following – oops!

So, it appears that I’ll need some sort of two stage approach the the constant-offset wall following problem, with an ‘approach’ stage and a ‘capture’ stage. If the measured distance is outside a predefined capture window (say +/- 2cm or so), then either the PID algorithm needs to be disabled entirely in favor of a constant-angle approach, or the PID parameters need to change to something more like Kp,Ki,Kd = 0,1,1 or something. More experimentation required.

Stay tuned,

Frank

WallE2 Robot in Arduino #include file hell

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Posted 02 February 2019

After a vacation from my WallE2 autonomous wall-following robot code to recover from rotator cuff surgery (and creating/testing my new digital tensionometer), a week or so ago I decided it was time to get back into WallE2 mode. At the time I thought this would be a piece of cake, as I had left WallE2 in pretty good shape, code-wise back in September 2018 (at least that’s what I thought!).

Instead, For the past couple of weeks I have been enduring what can only be described as “#include file hell”. The first time I tried to compile my main program, I saw a couple of warnings in an i2cDev related library. The code still compiled, but I take all warnings very seriously, and these weren’t there the last time I compiled the code.

So, I started trying to figure out what, if anything, had changed, and how to go about fixing whatever problem had caused the warnings to pop up. Unfortunately, everything I did made things worse – and worse – and worse. Nothing made sense. Jeff Rowberg, the creator of the fine i2cDev collection of i2c device drivers was mystified, as was Tim Leek, the main guy on the Visual Micro forum. Arggghhhh!

So, Jeff Rowberg suggested I try compiling the project in the Arduino IDE rather than in VS2017/Visual Micro, to eliminate any issues caused by that environment. Up until this point I had actually never used the Arduino IDE, much preferring the more helpful and feature rich VS2017/Visual Micro IDE. But, what the heck – how hard could it be?

Well, the answer was – DAMNED HARD! Using the Arduino IDE after the VS/VM environment was like moving backwards in time from the 21st century to the stone age – having to rub sticks together to make a compile happen! Moreover, the Arduino IDE created even more (and different) problems than I had experienced so far, meaning that I not only wasn’t draining the swamp, but the alligators were getting even more numerous! Some of the ‘features’ of the Arduino IDE:

When the IDE is first launched, it comes up with the last .INO file loaded. If you want a different file, it launches a new IDE instance with file->open; soon your desktop is littered with IDE instances.
When it tries to find a library based on a ‘#include <libraryName.h>’ line, it can’t handle [library name]-master as is common with libraries downloaded from GitHub
It requires exact name matching, including capitalization. So ‘#include <libraryName>’ will not match with the ‘Arduino\Libraries\Libraryname’ folder.
Editing is clunky, and there’s no such thing as Intellisense.

After running around in circles with my hair on fire for the last week or so, making my wife miserable with my griping and inundating Tim Leek and Jeff Rowberg with ever-more-desperate cries for help, I finally decided that I was simply going to have to start over from scratch with my robot program (some 3000+ lines of code in the main program and over a dozen custom libraries), and just build it up piece by piece until everything works again – groan. It’s not like I don’t have backups and wasn’t using revision control – I do and I was; it’s just that the programs that compiled cleanly back in September are generating warnings and errors now, and everything I do makes the problem worse!

Since the original problem seemed to be related to the library that runs the DFRobots MPU6050 module, I decided to start there. After struggling up the learning curve on the Arduino IDE, I also decided I would make sure that each program step would compile cleanly in both the VS/VM and Arduino IDE’s before proceeding to the next step. I reasoned that since the Arduino IDE is much pickier about library locations and names, I could use it as sort of an editorial check on VS/VM; if it works in the Arduino IDE, the VS/VM setup will have no problem.

For the DFRobots MPU6050 6DOF IMU module, I started with Jeff Rowberg’s ‘MPU6050_DMP6.INO’ example program buried way down in the ‘i2cdevlib-master\Arduino\MPU6050\examples\MPU6050_DMP6’. According to the i2cDev ReadMe, I could either put the entire i2cDev-master folder in Arduino\Libraries and let the linker figure it out, or just put the required files in the project (solution folder for VS/VM, ‘sketchbook folder’ for Arduino IDE) folder. I elected for the latter (local files) option, as I was at least a little suspicious that part or all of my original problem was caused by the compiler/linker loading from the wrong library folder in the i2dDev folder tree. In addition, I completely removed the i2cDev folder tree from my PC and re-downloaded it from GitHub, placing it in a completely unrelated folder so that neither environment could possibly find it. Then I copied the required header/.cpp files from the hidden i2cDev folder tree into the project folder. In VS/VM I created a project called ‘MPU6050_DMP6_Example’ and copied the Arduino versions of I2Cdev.cpp/.h, MPU6050.cpp/.h, MPU6050_6Axis_Motion.h, and helper_3dmath.h into it. Then I started working to get this project to compile both in the VS/VM & Arduino IDE’s.

I’ve now gotten it to compile and link in the Arduino IDE (albeit with the same warnings I started with just before I went down the rabbit hole into header file hell). However, I can’t get it to compile in VS/VM – it blows a whole bunch of errors of the form – apparently one error for each MP6050 function)

cc51VoHg.ltrans0.ltrans.o*: In function main
   (.text.startup+0x1e4): undefined reference to MPU6050::initialize()
   (.text.startup+0x234): undefined reference to MPU6050::testConnection()
   (.text.startup+0x294): undefined reference to MPU6050::reset()
   (.text.startup+0x2a8): undefined reference to MPU6050::setSleepEnabled(bool)

cc51VoHg.ltrans0.ltrans.o*: In function main

(.text.startup+0x1e4): undefined reference to MPU6050::initialize()

(.text.startup+0x234): undefined reference to MPU6050::testConnection()

(.text.startup+0x294): undefined reference to MPU6050::reset()

(.text.startup+0x2a8): undefined reference to MPU6050::setSleepEnabled(bool)

These errors proved impossible to correct, and nobody on either the Arduino or Visual Micro forums seemed to be able to help. Finally in desperation I uninstalled and re-installed the Visual Micro extension to VS2017, and that didn’t solve the problem either – exactly the same behavior.

So, last night I uninstalled VS2017 entirely from my system, and deleted the entire contents of the temp folder being used for temporary compile files. On my system this was C:\Users\Frank\AppData\Local\Temp.

03 February 2019

This morning I reinstalled VS2017CE and, using the Tools & Extensions menu, reinstalled Visual Micro. I left everything pretty much at the default settings (including the IDE selection and IDE location entries). The only thing non-standard with the setup was the inclusion of ‘https://raw.githubusercontent.com/sparkfun/Arduino_Boards/master/IDE_Board_Manager/package_sparkfun_index.json’ in the ‘Optional additional boards manager urls’ field. This was apparently left over from my previous installation. I’m not worried about this particular setting, but it does indicate that not everything about the previous incarnation of Visual Micro was actually removed from my system.

After installing VS/VM, I ran through a few of my simpler projects, and so far they have all compiled w/o problems (or had understandable and easily fixable problems). I also compiled each program in the Arduino IDE, taking care to follow the Arduino IDE restrictions (no “-master” in library folder names, exact capitalization, etc).

BlinkTest.ino – very simple, no #includes
ClassTest.ino – Very simple class construction project – no #includes
DigitalScale.ino – Several #includes, including the HX-711 load cell library
StepperSpeedCtrl – uses #include <Stepper.h>
AdaFruit_BTLE_UART_Test.ino – uses 7 different library #includes
Arduino_IMU6050_Test4.ino – uses i2cDev and MPU6050 libraries, along with SBWire, elapsedMillis, and PrintEx. this compiled OK, but with the same warnings (overrun & ‘one definition rule’) as when I first started this odyssey. Fortunately, that’s all that happened – I didn’t get the ‘(.text.startup+0x1e4): undefined reference to MPU6050::initialize()’ error – yay! This program also compiles in the Arduino IDE, with the same exact warnings. So, it appears I may be back where I started on this odyssey, with a program using the MPU6050 libraries that compiles OK but with one understandable/fixable warning (the overrun warning) and one mystery warning (the ‘one definition rule’ warning)

MPU6050_DMP6_Example: spoke too soon! This program blows the same ‘(.text.startup+0x1e4): undefined reference to MPU6050::initialize()’ errors as before in VM, but compiles fine (albeit with the same two warnings as always) in the Arduino IDE.
Arduino_IMU6050_Test4: This is a program I created some time ago, and I found that it compiles/links fine (stil with the overrun/ODR warnings), both VS/VM and Arduino IDE

In desperation, I decide to create a completely new Arduino project in VS/VM, copy the ‘known-good’ code from Arduino_IMU6050_Test4 into it, and then start hacking it down to the point where it fails. Surprise surprise, when I did this, the new project (UnDefTest2) failed right away in VS/VM, blowing LOTS of linker errors! Moreover, it compiled/linked fine in Arduino IDE – how could this be? There MUST be something different about the VS/VM environment between Arduino_IMU6050_Test4 and UnDefTest4 – but what? After putting the two projects up side-by-side (this is where a dual monitor setup comes in REAL handy), I finally twigged to the difference; in the ‘working’ version, the local header/cpp files had been ‘added’ to the project’s ‘Header Files’ and ‘Source Files’ folders via the Solution Explorer (right-click on the folder icon, select ‘Add Existing…’, select the desired files, click OK). As soon as I added the relevant files to the UnDefTest4 project, it compiled/linked fine – YAY!!

I could not believe what I was seeing! For some reason, VS/VM refused to process header/cpp files in the same folder as the .INO file, even though I had carefully checked the ‘Local Files Override Library Files’ option in the ‘Vmicro->Compiler’ menu. At the same time, the Arduino IDE always searches the local folder before anything else, so simply placing the relevant files in the local folder does the trick. The fact that Visual Micro requires an additional (and non-intuitive) step for this boggles the mind.

04 February 2019

OK, when I started all this foolishness I was trying to find out (and fix) whatever was causing the ‘One Definition Rule’ (ODR) violation warning I was getting on all my programs that used the MPU6050. I really really hate warnings, and I was determined to get to the bottom of this, and I finally did!

The ‘one definition rule’ (ODR) warning is caused when the compiler/linker sees code that can produce two different definitions for the same object. If that can happen, EVER, then an ODR violation warning is issued. Believe it or not, that is exactly what happens when the compiler processes MPU6050.H – it sees that there are some conditions for which two different descriptions of the MPU6050 class could exist – and says “no no”. The relevant portion of the class definition is shown below:

  private:
        uint8_t devAddr;
        uint8_t buffer[14];
    #if defined(MPU6050_INCLUDE_DMP_MOTIONAPPS20) or defined(MPU6050_INCLUDE_DMP_MOTIONAPPS41)
        uint8_t *dmpPacketBuffer;
        uint16_t dmpPacketSize;
    #endif

private:

uint8_t devAddr;

uint8_t buffer[14];

#if defined(MPU6050_INCLUDE_DMP_MOTIONAPPS20) or defined(MPU6050_INCLUDE_DMP_MOTIONAPPS41)

uint8_t *dmpPacketBuffer;

uint16_t dmpPacketSize;

#endif

When the compiler sees these lines, it says to itself; “Hmm, the way this is written, it is theoretically possible for there to exist two different versions of ‘Class MPU6050’, one with just two private member variables (devAddr & buffer) and one with four (with the addition of dmpPacketBuffer & dmpPacketSize), and this is a strict no-no; I’m going to whack that programmer across the head with an ODR violation!”

If the #ifdefined and #endif lines are commented out – the ODR warning goes away

Now, I suspect nobody has ever had a problem with this issue, as it would be very unlikely to have a project where BOTH versions of MPU6050 are in play, but of course the compiler doesn’t see it this way.

On a slightly different, but related subject, the OTHER warning was due to a potential integer overrun in the dmpGetGravity() function, as shown below:

uint8_t MPU6050::dmpGetGravity(int16_t *data, const uint8_t* packet) {
    /* +1g corresponds to +8192, sensitivity is 2g. */
    int16_t qI[4];
    uint8_t status = dmpGetQuaternion(qI, packet);
    data[0] = ((int32_t)qI[1] * qI[3] - (int32_t)qI[0] * qI[2]) / 16384;
    data[1] = ((int32_t)qI[0] * qI[1] + (int32_t)qI[2] * qI[3]) / 16384;
    data[2] = ((int32_t)qI[0] * qI[0] - (int32_t)qI[1] * qI[1]
	       - (int32_t)qI[2] * qI[2] + (int32_t)qI[3] * qI[3]) / (2 * 16384);
    return status;
}

uint8_t MPU6050::dmpGetGravity(int16_t *data, const uint8_t* packet) {

/* +1g corresponds to +8192, sensitivity is 2g. */

int16_t qI[4];

uint8_t status = dmpGetQuaternion(qI, packet);

data[0] = ((int32_t)qI[1] * qI[3] - (int32_t)qI[0] * qI[2]) / 16384;

data[1] = ((int32_t)qI[0] * qI[1] + (int32_t)qI[2] * qI[3]) / 16384;

data[2] = ((int32_t)qI[0] * qI[0] - (int32_t)qI[1] * qI[1]

- (int32_t)qI[2] * qI[2] + (int32_t)qI[3] * qI[3]) / (2 * 16384);

return status;

}

if the last line of the above calculation is changed to (note the addition of ‘UL’)
– (int32_t)qI[2] * qI[2] + (int32_t)qI[3] * qI[3]) / (2 * 16384UL);
then this warning goes away as well.

Mission accomplished! I now have MPU6050 code that compiles without errors (or warnings!!) in both the VS/VM and Arduino IDE environments. Along the way I learned more than I ever wanted to know about ‘One Definition Rule’ violations and the innards of both the VS/VM environment and the Arduino IDE.

to paraphrase a quote attributed to Abraham of 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.”

Stay tuned,

Frank

Digital Tension Scale, Part V

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posted 09 January 2019,

In my previous post on this subject I described the components I planned to use for my Digital Tension Scale project, and also the design for a box that would mount directly on the S-shaped load cell assembly.

This post describes the ‘final’ (to the extent than anything I do can be considered final) assembly of the completed system into my 3D-printed housing, and the results of some initial battery-powered testing.

As shown in the following photos, the major components (Teensy 3.2 microcontroller, HC-05 Bluetooth Module, HX-711 load cell amp/A-D, and Sparkfun ‘Basic’ LiPo Charger) were mounted on perfboard, which was then in turn attached to the box lid via a set of custom-printed standoffs. A short piece of ribbon cable connects the Teensy to the LCD display. The general idea behind this physical layout is to allow easy access to the electronics for troubleshooting, and to allow for battery charging and/or Teensy programming without having to open the box.

3D-printed housing. Note the glow from the Sparkfun charger LED

View of housing showing the access port for supplying USB power and/or programming the Teensy

View with the lid and electronics board removed. The LCD display is face down in its cutout

Exploded view showing all system components

Showing connections from load cell to HX-711

Top view showing how load cell attaches to the housing

Closeup showing load cell lead routing and power/programming port

End view showing charging port

Preliminary Testing Results:

At this point I have everything running on battery power only inside the box, and I have been able to demonstrate remote data capture on my PC using the HC-05 BT link. The following image shows the data taken from my rowing machine, and a short video demonstrating the setup.

Complete Code:

Here is the complete Teensy 3.2 program as it stands today. As you can see if you inspect the code, I have the Teensy low-power stuff turned OFF for the moment (that’s the purpose of the ‘#define NO_SNOOZE’ statement.

/*
    Name:       TeensyLowPowerDigitalScale.ino
    Created:	12/2/2018 9:43:43 PM
    Author:     FRANKWIN10\Frank
*/

//12/27/18 Added bluetooth support via Serial1
//12/27/18 Added calibration code from TeensyDigitalCalibration.ino

/*
	Name:       DigitalScaleAutoCal.ino
	Created:	11/15/2018 4:49:12 PM
	Author:     FRANKWIN10\Frank

	This program is a modification of the November 2016 circuits4you.com program for interfacing
	with the HX711 Module coupled with a typical load cell.  It's purpose is to automatically
	calibrate the combination to accurately display weight in Kg.
	The process is as follows:
	Step1:	User opts to calibrate by entering 'Y' at the prompt.  Entering any other key (or
			just letting the question time out) will skip the calibration process
	Step2:  User establishes 'tare' weight physical configuration with any non-measured weight
			attached (in my case, the bucket used to hold measured amounts of water used for
			weight calibration), and then presses 'T' to zero out the 'tare weight'
	Step3:	The user establishes a calibration weight condition (in my case, 1.8 liters of water)
			and enters the weight value (in Kg).  The program then calculates the scale factor
			needed to calibrate the scale for the entered weight and then automatically
			drops into measurement mode
	Step5:	The user enters 'q' to quit measurements.

*/

/*
I need to combine the calibration code from TeensyDigitalScaleCalibration.ino with this
program, so I can run the cal procedure by sending a character or two from my PC or phone.
No character, no calibration.
*/
#pragma region DEBUG_DEFINES
#define NO_SNOOZE

#pragma endregion Debugging Defines


#pragma region CAL_SUPPORT
#include <elapsedMillis.h>

elapsedMillis sinceLastWaitMsg;
const int WAITINGMSGINTERVALMSEC = 1000; //1-sec intervals
const int MAX_WAITING_INTERVALS = 10; //how long to wait before starting measurement
const int BUFLEN = 20;
int numWaitIntervals = 0;

char inbuf[BUFLEN]; //buffer for user input
char inbuf1[BUFLEN];//buffer for serial1 input

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands
bool bDoneMeasuring = false;
const char* waitstr = "Waiting...Measurements will start in ";
#pragma endregion Calibration Support


#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_PCD8544.h>

#pragma region LOW_POWER_SUPP
//12/03/18 added for low power mode
#include <Snooze.h>
// Load just the 'timer' wake-up driver
SnoozeTimer timer;
SnoozeUSBSerial usb;
SnoozeBlock config_teensy32(usb, timer);
const int SLEEP_TIME_MSEC = 5000;
const float INACTIVE_SCALE_THRESHOLD_KG = 1.f;
//const float INACTIVE_SCALE_THRESHOLD_KG = -10.f;
//const int MIN_INACTIVE_SCALE_COUNT = 100;
const int MIN_INACTIVE_SCALE_COUNT = 20;
const int BLUETOOTH_POWER_PIN = 12;
int numInactiveScaleCounts = 0;

#pragma endregion Low Power Support

#pragma region LOAD_CELL
#include "HX711.h"  //You must have this library in your arduino library folder
#include <EEPROM.h>
#include<EEPROMAnything.h> //so I can read the last calibration value from EEPROM
#define DOUT  A1
#define CLK  A0
HX711 scale(DOUT, CLK);

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands
long calibration_factor = -96650; //-106600 worked for my 40Kg max scale setup
long tare_offset = 0;
const int LED_PIN = 13;
const int CAL_FACTOR_EEPROM_ADDR = 0;
const int TARE_OFFSET_EEPROM_ADDR = CAL_FACTOR_EEPROM_ADDR + sizeof(calibration_factor);
float scaleKg = 0;
float vBatt = 0;
#pragma endregion Load Cell Support

#pragma region LCD_DISPLAY
// Hardware SPI (faster, but must use certain hardware pins):
// Note with hardware SPI MISO and SS pins aren't used but will still be read
// and written to during SPI transfer.  Be careful sharing these pins!
// SCK is LCD serial clock (SCLK) - this is pin 13 on Arduino Uno
// MOSI is LCD DIN - this is pin 11 on an Arduino Uno
// pin 6 - Data/Command select (D/C)
// pin 5 - LCD chip select (CS)
// pin 4 - LCD reset (RST)
const int LCD_DC_PIN = 6;
const int LCD_CS_PIN = 5;
const int LCD_RST_PIN = 4;
//const int SPI_DOUT_PIN = 11;
const int SPI_SCK_PIN = A0;
//const int SPI_SCK_PIN = 12;
const int LCD_BACKLIGHT_PIN = 3;

//Adafruit_PCD8544 display = Adafruit_PCD8544(6, 5, 4);//11/25/18
Adafruit_PCD8544 display = Adafruit_PCD8544(LCD_DC_PIN, LCD_CS_PIN, LCD_RST_PIN);//12/16/18 chg to identifiers
#pragma endregion Noki LCD Display

#pragma region BATT_FUEL_GUAGE
const int BATT_SYMBOL_X = 68;
const int BATT_SYMBOL_Y = 1;
const int BATT_SYMBOL_H = 8;
const int BATT_SYMBOL_W = 16;
const int DEFAULT_CHAR_HEIGHT = 8;
const int DEFAULT_CHAR_WIDTH = 5;
const int DEFAULT_CHAR_SIZE = 2;

//added 12/03/18 for battV measurements
//12/06/18 changed to internal 1.2V reference and 30K:10K divider
const int BATTV_READ_PIN = A7;
const int DEAD_BATT_COUNTS = 642;
const int FULL_BATT_COUNTS = 887;
const float FULL_BATT_VOLTS = 4.2;
const float DEAD_BATT_VOLTS = 3.0;
const float VOLTS_PER_COUNT = (FULL_BATT_VOLTS - DEAD_BATT_VOLTS) / (FULL_BATT_COUNTS - DEAD_BATT_COUNTS);
#pragma endregion Battery Fuel Guage



void setup() 
{
	Serial.begin(115200);
	delay(1000); //need this to get serial printout

	Serial.println("Welcome to the Teensy Low Power Digital Scale Program");

	Serial1.begin(9600);
	Serial1.println("Welcome via Bluetooth!");


	//initialize load cell and retrieve cal/tar values from EEPROM
	EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM
	Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);
	scale.set_scale(calibration_factor);

	EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM
	Serial.printf("The current stored tare offset factor is %li\n", tare_offset);
	scale.set_offset(tare_offset);

	if (IsCalibrationRequired(5)) //number of time intervals to wait
	{
		if (DoCalibration(10, 20)) //01/03/19 added numwait params to sig
		{
			Serial.printf("Calibration completed successfully... Starting Measurements\n\n");
			Serial1.printf("Calibration completed successfully... Starting Measurements\n\n");
		}
		else
		{
			Serial.printf("Calibration Failed - Measurements may be invalid!\n\n");
			Serial1.printf("Calibration Failed - Measurements may be invalid!\n\n");

		}


		Serial.printf("Time(mSec)\tWt(Kg)\n");
	}


	/********************************************************
	 Set Low Power Timer wake up in milliseconds.
	 ********************************************************/
	timer.setTimer(SLEEP_TIME_MSEC);// milliseconds

	//12/04/18 added code to set analog reference to internal 1.2V source
	analogReference(INTERNAL1V1);
	//initialize LCD display
	display.begin();
	display.setContrast(60); //pretty dark
	display.setTextSize(1);
	display.setTextColor(BLACK);
	display.setCursor(0, 0);

	display.display(); //first time - shows the Adafruit logo
	delay(1000); //show Adafruit logo for 1 sec
	display.clearDisplay();   // clears the screen and buffer
	display.display(); //first time - shows the Adafruit logo

	display.setCursor(0, 0);
	display.println("Hello LCD!");
	display.display();

	pinMode(BLUETOOTH_POWER_PIN, OUTPUT);
	digitalWrite(BLUETOOTH_POWER_PIN, HIGH); //enable the bluetooth module

	//01/09/19 make sure the backlight LED is OFF
	pinMode(LCD_BACKLIGHT_PIN, OUTPUT);
	digitalWrite(LCD_BACKLIGHT_PIN, LOW);
}


void loop()
{
	//12/06/18 now using 30K/10K voltage divider on A7 and 1.2V ref.
	display.clearDisplay(); //clear memory bitmap
	display.setCursor(0, 0);
	vBatt = UpdateBatteryDisplay();
	//scaleKg = UpdateScaleDisplay();
	scaleKg = scale.get_units(3);
	Serial1.printf("%5.3f\r\n", scaleKg); //to BT module
	Serial.printf("%5.3f\n", scaleKg); //to serial console
	display.print(scaleKg); display.println(" Kg");//to LCD display
	display.display();

#ifndef NO_SNOOZE

	//if the scale has been quiet for a while, go to sleep
	if (scaleKg <= INACTIVE_SCALE_THRESHOLD_KG)
	{
		numInactiveScaleCounts++;
		if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)
		{
			numInactiveScaleCounts = MIN_INACTIVE_SCALE_COUNT;
		}
	}
	else
	{
		numInactiveScaleCounts = 0; //one active measurment wakes everything up
	}

	if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)
	{
		Serial.printf("Going to sleep at %li mSec\n", millis());
		delay(1000); //needed to get the print out the door before sleeping

		//01/04/18 added to disable bluetooth module while sleeping
		digitalWrite(BLUETOOTH_POWER_PIN, LOW);
		display.clearDisplay();
		display.display();
		Snooze.sleep(config_teensy32); //sleep
	}

#endif // !NO_SNOOZE

	if (digitalRead(BLUETOOTH_POWER_PIN) == LOW)
	{
		digitalWrite(BLUETOOTH_POWER_PIN, HIGH); //re-enable the BT module
	}

	delay(100);
}

float UpdateScaleDisplay()
{
	float kG = scale.get_units(3);
	//float kG = (float)random(0,40);
	display.print(kG); display.println(" Kg");
	return kG;
}

float UpdateBatteryDisplay()
{
	int batt_counts = analogRead(BATTV_READ_PIN);
	float batt_volts = DEAD_BATT_VOLTS + (batt_counts - DEAD_BATT_COUNTS) * VOLTS_PER_COUNT;
	display.print(batt_volts); display.println(" V");
	UpdateBatterySymbol(batt_volts);
	return batt_volts;
}


void UpdateBatterySymbol(float vbatt)
{
	//Purpose: Update the battery symbol to show current charge state
	//Inputs: 
	//	vbatt = current battery voltage
	//	FULL_BATT_VOLTS = fully charged battery voltage
	//	DEAD_BATT_VOLTS = fully discharged battery voltage
	//	BATT_SYMBOL_X/Y/H/W = battery symbol loc/dims
	//Outputs: Updated battery symbol
	//Plan:
	//	Step1: draw open rect for battery symbol outline
	//	Step2: draw filled rect indicating charge state
	//	Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

//Step1: draw open rect for battery symbol outline
	display.drawRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, BATT_SYMBOL_W, BATT_SYMBOL_H, 1);

	//Step2: draw filled rect indicating charge state
	float Vrange = FULL_BATT_VOLTS - DEAD_BATT_VOLTS;
	int fillWidth = (int)(BATT_SYMBOL_W * ((vbatt - DEAD_BATT_VOLTS) / Vrange) + 0.5f);
	//Serial.printf("vbat, fillW = %4.2f,%d\n", vbatt, fillWidth);
	display.fillRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, fillWidth, BATT_SYMBOL_H, 1);

	//Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol
	if (vbatt <= DEAD_BATT_VOLTS)
	{
		//try drawing lines from corner to corner
		int ulX = BATT_SYMBOL_X;
		int ulY = BATT_SYMBOL_Y;
		int urX = BATT_SYMBOL_X + BATT_SYMBOL_W;
		int urY = ulY;
		int lrX = urX;
		int lrY = urY + BATT_SYMBOL_H;
		int llX = ulX;
		int llY = lrY;

		display.drawLine(ulX, ulY, lrX, lrY, 1);
		display.drawLine(llX, llY, urX, urY, 1);
	}
}

bool IsCalibrationRequired(int numWaitIntervals)
{
	//Purpose:  Determine if the user wishes to run the cal procedure
	//Inputs: Serial and Serial1 (Serial is the normal PC serial port, Serial1 is Bluetooth
	//Outputs: returns TRUE if a 'y/Y' is received from either serial port within a 
	//		   few seconds of power-up.
	//Plan:
	//	Step1:  Send the 'do you wish to calibrate' message to both ports
	//	Step2:	Watch for activity until timeout expires.  If nothing received,
	//			return FALSE. If a 'y' or 'Y' is received, return TRUE

	bool result = false;

//Step1:  Send the 'do you wish to calibrate' message to both ports

	//normal PC serial monitor port
	Serial.printf("Enter 'Y' to start the calibration, any other key to skip\n");
	Serial.printf("Calibrate (Y/N) (N)?\n");

	//Bluetooth serial port
	Serial1.printf("Enter 'Y' to start the calibration, any other key to skip\r\n");
	Serial1.printf("Calibrate (Y/N) (N)?\r\n");

	//Step2:  Watch for activity until timeout expires.  If nothing received,
	//			return FALSE. If a 'y' or 'Y' is received, return TRUE
	int intervalCount = 0;
	sinceLastWaitMsg = 0;

	memset(inbuf, 0, BUFLEN);
	memset(inbuf1, 0, BUFLEN);
	Serial.printf("inbuf = %s, inbuf1 = %s\n", inbuf, inbuf1);


	while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)
		&& intervalCount < numWaitIntervals) //returns true if strlen(inbuf) > 0
	{
		if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)
		{
			sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;
			intervalCount++;
			Serial.printf("%s %d\n", waitstr, numWaitIntervals - intervalCount);
			Serial1.printf("%s %d\r\n", waitstr, numWaitIntervals - intervalCount); //bluetooth
		}
		delay(250);
	}

	Serial.printf("Received %s from Serial, %s from Serial1\n", inbuf, inbuf1);
	if (strncasecmp("Y", inbuf, 1) == 0 || strncasecmp("Y",inbuf1,1) == 0) //compare only 1st chars, as user input may have CR/LF appended
	{
		result = true;
	}

	return result;
}


bool GetUserInputStr0(char* inbuf)
{
	//Purpose: Get user input from Serial0
	//Inputs:
	//	inbuf = pointer to char[10] array to receive user input
	//Outputs:
	//	inbuf = String object containing user input.
	//	returns True if user input was received, False if the routine timed out
	//Plan:
	//	Wait for user input or timeout whichever occurs first
	//Notes:
	//	12/27/18 modified to work with both Serial & Serial1 ports.  We assume that 
	//			 userinput is coming from one port or the other, but not both
	//	01/02/19 re-written for cleaner code

	//Serial1.printf("In GetUserInputStr0\n");

	memset(inbuf, 0, BUFLEN);

	int readbyte = 0;
	int charidx = 0;
	while (Serial.available() && charidx < 100)
	{
		readbyte = Serial.read();
		inbuf[charidx] = readbyte;
		charidx++;
	}

	if (strlen(inbuf) > 0)
	{
		Serial.print("Received "); Serial.print(inbuf); Serial.println(" from Serial0");
	}

	return (charidx < 100 && strlen(inbuf) > 0);
}

bool GetUserInputStr1(char* inbuf1)
{
	//Purpose: Get user input from Serial1
	//Inputs:
	//	inbuf1 = pointer to char[10] array to receive user input from Serial1
	//Outputs:
	//	inbuf1 = String object containing user input from Serial1.
	//	returns True if user input was received, False if the routine timed out
	//Plan:
	//	Wait for user input or timeout whichever occurs first
	//Notes:
	//	12/30/18 coped from GetUserInput & modified to work with Serial1 ports
	//	01/02/19 re-written for cleaner code

	//Serial1.printf("In GetUserInputStr1\n");

	memset(inbuf1, 0, BUFLEN);

	int readbyte = 0;
	int charidx = 0;
	while (Serial1.available() && charidx < 100)
	{
		readbyte = Serial1.read();
		inbuf1[charidx] = readbyte;
		charidx++;
	}

	if (strlen(inbuf1) > 0)
	{
		Serial1.print("Received "); Serial1.print(inbuf1); Serial1.println(" from Serial1");
	}
	return (charidx < 100 && strlen(inbuf1) > 0);
}

bool DoCalibration(int numwait_tare, int numwait_weight)
{
	Serial.printf("Digital Scale Program\n");
	Serial.printf("Program to automatically calibrate HX711/Load Cell to measure weight in Kg\n");

	EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM
	Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);

	if (isnan((float)calibration_factor))
	{
		Serial.printf("invalid cal factor:  Setting to -96650\n");
		calibration_factor = -96650;
	}
	scale.set_scale(calibration_factor);

	EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM
	Serial.printf("The current stored tare offset factor is %li\n", tare_offset);

	if (isnan((float)tare_offset))
	{
		Serial.printf("invalid cal factor:  Setting to zero\n");
		tare_offset = 0;
	}
	scale.set_offset(tare_offset);

	//calibrate with known weights
	Serial.println("HX711 Calibration");
	Serial.println("Remove all non-fixture weight from scale, and press 't' to zero the scale");
	Serial.println("Or any other character to skip this step");
	Serial1.println("HX711 Calibration");
	Serial1.println("Remove all non-fixture weight from scale, and press 't' to zero the scale");
	Serial1.println("Or any other character to skip this step");

	memset(inbuf, 0, BUFLEN);
	memset(inbuf1, 0, BUFLEN);

	int intervalCount = 0;
	sinceLastWaitMsg = 0;
	while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)
		&& intervalCount < numwait_tare) //returns true if strlen(inbuf) > 0
	{
		if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)
		{
			sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;
			intervalCount++;
			Serial.printf("%s %d\n", waitstr, numwait_tare - intervalCount);
			Serial1.printf("%s %d\r\n", waitstr, numwait_tare - intervalCount); //bluetooth
		}
		delay(250);
	}

	if (strncasecmp("T", inbuf, 1) == 0 || strncasecmp("T", inbuf1,1) == 0) //compare only 1st chars, as user input may have CR/LF appended
	{
		tare_offset = scale.read_average(); //Get a baseline reading
		Serial.printf("Applying offset %li as tare adjustment\n", tare_offset);
		scale.set_offset(tare_offset); //this value will be subtracted from all future measurements
		Serial.printf("Writing offset %li to EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);
		EEPROM_writeAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);

		EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);
		Serial.printf("Read offset %li from EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);
	}

	Serial.println("Apply a known weight (the higher the better) and enter its value in Kg");
	Serial.println("Enter 0 to skip this step");

	Serial1.println("Apply a known weight (the higher the better) and enter its value in Kg");
	Serial1.println("Enter 0 to skip this step");

	memset(inbuf, 0, BUFLEN);
	memset(inbuf1, 0, BUFLEN);
	intervalCount = 0;
	sinceLastWaitMsg = 0;

	while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)
		&& intervalCount < numwait_weight) //returns true if strlen(inbuf) > 0
	{
		if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)
		{
			sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;
			intervalCount++;
			Serial.printf("%s %d\n", waitstr, numwait_weight - intervalCount);
			Serial1.printf("%s %d\r\n", waitstr, numwait_weight - intervalCount); //bluetooth
		}
		delay(250);
	}

	//calculate scale factor resulting in user-input wt
	//wt(Kg) = (read_avg - OFFSET)/Scale
	//Scale = (read_avg - OFFSET)/wt(Kg)

	double wtKg = 0;
	if (strlen(inbuf) > 0)
	{
		wtKg = atof(inbuf);
		Serial.printf("User weight input was %4.2f\n", wtKg);
	}
	else if(strlen(inbuf1) > 0)
	{
		wtKg = atof(inbuf1);
		Serial1.printf("User weight input was %4.2f\r\n", wtKg);
	}
	else
	{
		Serial.printf("No user input detected - using 0.00Kg\n");
		Serial1.printf("No user input detected - using 0.00Kg\r\n");
	}

	long read_avg = scale.read_average();
	long offset = scale.get_offset();
	calibration_factor = (double)(read_avg - offset) / wtKg;
	scale.set_scale(calibration_factor); //Adjust to this calibration factor

	Serial.printf("User weight input was %4.2f, read_avg = %li, offset = %li, cal = ",
		wtKg, read_avg, offset);
	Serial.println(calibration_factor); //PrintEx won't print the cal factor value

	Serial1.printf("User weight input was %4.2f, read_avg = %li, offset = %li, cal = ",
		wtKg, read_avg, offset);
	Serial1.println(calibration_factor); //PrintEx won't print the cal factor value

	EEPROM_writeAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);
	Serial.print("Wrote cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor
	Serial.printf(" to EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);
	Serial1.print("Wrote cal factor "); Serial1.print(calibration_factor); //Serial.printf doesn't work for cal factor
	Serial1.printf(" to EEPROM address %d\r\n", CAL_FACTOR_EEPROM_ADDR);


	EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);
	Serial.print("Read cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor
	Serial.printf(" from EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);
	Serial1.print("Read cal factor "); Serial1.print(calibration_factor); //Serial.printf doesn't work for cal factor
	Serial1.printf(" from EEPROM address %d\r\n", CAL_FACTOR_EEPROM_ADDR);

	Serial.printf("\n\nCalibration Complete\n");
	Serial1.printf("\n\nCalibration Complete\r\n");

	return true;
}

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Name: TeensyLowPowerDigitalScale.ino

Created: 12/2/2018 9:43:43 PM

Author: FRANKWIN10\Frank

//12/27/18 Added bluetooth support via Serial1

//12/27/18 Added calibration code from TeensyDigitalCalibration.ino

Name: DigitalScaleAutoCal.ino

Created: 11/15/2018 4:49:12 PM

Author: FRANKWIN10\Frank

This program is a modification of the November 2016 circuits4you.com program for interfacing

with the HX711 Module coupled with a typical load cell. It's purpose is to automatically

calibrate the combination to accurately display weight in Kg.

The process is as follows:

Step1: User opts to calibrate by entering 'Y' at the prompt. Entering any other key (or

just letting the question time out) will skip the calibration process

Step2: User establishes 'tare' weight physical configuration with any non-measured weight

attached (in my case, the bucket used to hold measured amounts of water used for

weight calibration), and then presses 'T' to zero out the 'tare weight'

Step3: The user establishes a calibration weight condition (in my case, 1.8 liters of water)

and enters the weight value (in Kg). The program then calculates the scale factor

needed to calibrate the scale for the entered weight and then automatically

drops into measurement mode

Step5: The user enters 'q' to quit measurements.

I need to combine the calibration code from TeensyDigitalScaleCalibration.ino with this

program, so I can run the cal procedure by sending a character or two from my PC or phone.

No character, no calibration.

#pragma region DEBUG_DEFINES

#define NO_SNOOZE

#pragma endregion Debugging Defines

#pragma region CAL_SUPPORT

#include <elapsedMillis.h>

elapsedMillis sinceLastWaitMsg;

const int WAITINGMSGINTERVALMSEC = 1000; //1-sec intervals

const int MAX_WAITING_INTERVALS = 10; //how long to wait before starting measurement

const int BUFLEN = 20;

int numWaitIntervals = 0;

char inbuf[BUFLEN]; //buffer for user input

char inbuf1[BUFLEN];//buffer for serial1 input

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands

bool bDoneMeasuring = false;

const char* waitstr = "Waiting...Measurements will start in ";

#pragma endregion Calibration Support

#include <SPI.h>

#include <Adafruit_GFX.h>

#include <Adafruit_PCD8544.h>

#pragma region LOW_POWER_SUPP

//12/03/18 added for low power mode

#include <Snooze.h>

// Load just the 'timer' wake-up driver

SnoozeTimer timer;

SnoozeUSBSerial usb;

SnoozeBlock config_teensy32(usb, timer);

const int SLEEP_TIME_MSEC = 5000;

const float INACTIVE_SCALE_THRESHOLD_KG = 1.f;

//const float INACTIVE_SCALE_THRESHOLD_KG = -10.f;

//const int MIN_INACTIVE_SCALE_COUNT = 100;

const int MIN_INACTIVE_SCALE_COUNT = 20;

const int BLUETOOTH_POWER_PIN = 12;

int numInactiveScaleCounts = 0;

#pragma endregion Low Power Support

#pragma region LOAD_CELL

#include "HX711.h" //You must have this library in your arduino library folder

#include <EEPROM.h>

#include<EEPROMAnything.h> //so I can read the last calibration value from EEPROM

#define DOUT A1

#define CLK A0

HX711 scale(DOUT, CLK);

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands

long calibration_factor = -96650; //-106600 worked for my 40Kg max scale setup

long tare_offset = 0;

const int LED_PIN = 13;

const int CAL_FACTOR_EEPROM_ADDR = 0;

const int TARE_OFFSET_EEPROM_ADDR = CAL_FACTOR_EEPROM_ADDR + sizeof(calibration_factor);

float scaleKg = 0;

float vBatt = 0;

#pragma endregion Load Cell Support

#pragma region LCD_DISPLAY

// Hardware SPI (faster, but must use certain hardware pins):

// Note with hardware SPI MISO and SS pins aren't used but will still be read

// and written to during SPI transfer. Be careful sharing these pins!

// SCK is LCD serial clock (SCLK) - this is pin 13 on Arduino Uno

// MOSI is LCD DIN - this is pin 11 on an Arduino Uno

// pin 6 - Data/Command select (D/C)

// pin 5 - LCD chip select (CS)

// pin 4 - LCD reset (RST)

const int LCD_DC_PIN = 6;

const int LCD_CS_PIN = 5;

const int LCD_RST_PIN = 4;

//const int SPI_DOUT_PIN = 11;

const int SPI_SCK_PIN = A0;

//const int SPI_SCK_PIN = 12;

const int LCD_BACKLIGHT_PIN = 3;

//Adafruit_PCD8544 display = Adafruit_PCD8544(6, 5, 4);//11/25/18

Adafruit_PCD8544 display = Adafruit_PCD8544(LCD_DC_PIN, LCD_CS_PIN, LCD_RST_PIN);//12/16/18 chg to identifiers

#pragma endregion Noki LCD Display

#pragma region BATT_FUEL_GUAGE

const int BATT_SYMBOL_X = 68;

const int BATT_SYMBOL_Y = 1;

const int BATT_SYMBOL_H = 8;

const int BATT_SYMBOL_W = 16;

const int DEFAULT_CHAR_HEIGHT = 8;

const int DEFAULT_CHAR_WIDTH = 5;

const int DEFAULT_CHAR_SIZE = 2;

//added 12/03/18 for battV measurements

//12/06/18 changed to internal 1.2V reference and 30K:10K divider

const int BATTV_READ_PIN = A7;

const int DEAD_BATT_COUNTS = 642;

const int FULL_BATT_COUNTS = 887;

const float FULL_BATT_VOLTS = 4.2;

const float DEAD_BATT_VOLTS = 3.0;

const float VOLTS_PER_COUNT = (FULL_BATT_VOLTS - DEAD_BATT_VOLTS) / (FULL_BATT_COUNTS - DEAD_BATT_COUNTS);

#pragma endregion Battery Fuel Guage

void setup()

{

Serial.begin(115200);

delay(1000); //need this to get serial printout

Serial.println("Welcome to the Teensy Low Power Digital Scale Program");

Serial1.begin(9600);

Serial1.println("Welcome via Bluetooth!");

//initialize load cell and retrieve cal/tar values from EEPROM

EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM

Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);

scale.set_scale(calibration_factor);

EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM

Serial.printf("The current stored tare offset factor is %li\n", tare_offset);

scale.set_offset(tare_offset);

if (IsCalibrationRequired(5)) //number of time intervals to wait

{

if (DoCalibration(10, 20)) //01/03/19 added numwait params to sig

{

Serial.printf("Calibration completed successfully... Starting Measurements\n\n");

Serial1.printf("Calibration completed successfully... Starting Measurements\n\n");

}

else

{

Serial.printf("Calibration Failed - Measurements may be invalid!\n\n");

Serial1.printf("Calibration Failed - Measurements may be invalid!\n\n");

}

Serial.printf("Time(mSec)\tWt(Kg)\n");

}

/********************************************************

Set Low Power Timer wake up in milliseconds.

********************************************************/

timer.setTimer(SLEEP_TIME_MSEC);// milliseconds

//12/04/18 added code to set analog reference to internal 1.2V source

analogReference(INTERNAL1V1);

//initialize LCD display

display.begin();

display.setContrast(60); //pretty dark

display.setTextSize(1);

display.setTextColor(BLACK);

display.setCursor(0, 0);

display.display(); //first time - shows the Adafruit logo

delay(1000); //show Adafruit logo for 1 sec

display.clearDisplay(); // clears the screen and buffer

display.display(); //first time - shows the Adafruit logo

display.setCursor(0, 0);

display.println("Hello LCD!");

display.display();

pinMode(BLUETOOTH_POWER_PIN, OUTPUT);

digitalWrite(BLUETOOTH_POWER_PIN, HIGH); //enable the bluetooth module

//01/09/19 make sure the backlight LED is OFF

pinMode(LCD_BACKLIGHT_PIN, OUTPUT);

digitalWrite(LCD_BACKLIGHT_PIN, LOW);

}

void loop()

{

//12/06/18 now using 30K/10K voltage divider on A7 and 1.2V ref.

display.clearDisplay(); //clear memory bitmap

display.setCursor(0, 0);

vBatt = UpdateBatteryDisplay();

//scaleKg = UpdateScaleDisplay();

scaleKg = scale.get_units(3);

Serial1.printf("%5.3f\r\n", scaleKg); //to BT module

Serial.printf("%5.3f\n", scaleKg); //to serial console

display.print(scaleKg); display.println(" Kg");//to LCD display

display.display();

#ifndef NO_SNOOZE

//if the scale has been quiet for a while, go to sleep

if (scaleKg <= INACTIVE_SCALE_THRESHOLD_KG)

{

numInactiveScaleCounts++;

if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)

{

numInactiveScaleCounts = MIN_INACTIVE_SCALE_COUNT;

}

else

{

numInactiveScaleCounts = 0; //one active measurment wakes everything up

}

if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)

{

Serial.printf("Going to sleep at %li mSec\n", millis());

delay(1000); //needed to get the print out the door before sleeping

//01/04/18 added to disable bluetooth module while sleeping

digitalWrite(BLUETOOTH_POWER_PIN, LOW);

display.clearDisplay();

display.display();

Snooze.sleep(config_teensy32); //sleep

}

#endif // !NO_SNOOZE

if (digitalRead(BLUETOOTH_POWER_PIN) == LOW)

{

digitalWrite(BLUETOOTH_POWER_PIN, HIGH); //re-enable the BT module

}

delay(100);

}

float UpdateScaleDisplay()

{

float kG = scale.get_units(3);

//float kG = (float)random(0,40);

display.print(kG); display.println(" Kg");

return kG;

}

float UpdateBatteryDisplay()

{

int batt_counts = analogRead(BATTV_READ_PIN);

float batt_volts = DEAD_BATT_VOLTS + (batt_counts - DEAD_BATT_COUNTS) * VOLTS_PER_COUNT;

display.print(batt_volts); display.println(" V");

UpdateBatterySymbol(batt_volts);

return batt_volts;

}

void UpdateBatterySymbol(float vbatt)

{

//Purpose: Update the battery symbol to show current charge state

//Inputs:

// vbatt = current battery voltage

// FULL_BATT_VOLTS = fully charged battery voltage

// DEAD_BATT_VOLTS = fully discharged battery voltage

// BATT_SYMBOL_X/Y/H/W = battery symbol loc/dims

//Outputs: Updated battery symbol

//Plan:

// Step1: draw open rect for battery symbol outline

// Step2: draw filled rect indicating charge state

// Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

//Step1: draw open rect for battery symbol outline

display.drawRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, BATT_SYMBOL_W, BATT_SYMBOL_H, 1);

//Step2: draw filled rect indicating charge state

float Vrange = FULL_BATT_VOLTS - DEAD_BATT_VOLTS;

int fillWidth = (int)(BATT_SYMBOL_W * ((vbatt - DEAD_BATT_VOLTS) / Vrange) + 0.5f);

//Serial.printf("vbat, fillW = %4.2f,%d\n", vbatt, fillWidth);

display.fillRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, fillWidth, BATT_SYMBOL_H, 1);

//Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

if (vbatt <= DEAD_BATT_VOLTS)

{

//try drawing lines from corner to corner

int ulX = BATT_SYMBOL_X;

int ulY = BATT_SYMBOL_Y;

int urX = BATT_SYMBOL_X + BATT_SYMBOL_W;

int urY = ulY;

int lrX = urX;

int lrY = urY + BATT_SYMBOL_H;

int llX = ulX;

int llY = lrY;

display.drawLine(ulX, ulY, lrX, lrY, 1);

display.drawLine(llX, llY, urX, urY, 1);

}

bool IsCalibrationRequired(int numWaitIntervals)

{

//Purpose: Determine if the user wishes to run the cal procedure

//Inputs: Serial and Serial1 (Serial is the normal PC serial port, Serial1 is Bluetooth

//Outputs: returns TRUE if a 'y/Y' is received from either serial port within a

// few seconds of power-up.

//Plan:

// Step1: Send the 'do you wish to calibrate' message to both ports

// Step2: Watch for activity until timeout expires. If nothing received,

// return FALSE. If a 'y' or 'Y' is received, return TRUE

bool result = false;

//Step1: Send the 'do you wish to calibrate' message to both ports

//normal PC serial monitor port

Serial.printf("Enter 'Y' to start the calibration, any other key to skip\n");

Serial.printf("Calibrate (Y/N) (N)?\n");

//Bluetooth serial port

Serial1.printf("Enter 'Y' to start the calibration, any other key to skip\r\n");

Serial1.printf("Calibrate (Y/N) (N)?\r\n");

//Step2: Watch for activity until timeout expires. If nothing received,

// return FALSE. If a 'y' or 'Y' is received, return TRUE

int intervalCount = 0;

sinceLastWaitMsg = 0;

memset(inbuf, 0, BUFLEN);

memset(inbuf1, 0, BUFLEN);

Serial.printf("inbuf = %s, inbuf1 = %s\n", inbuf, inbuf1);

while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)

&& intervalCount < numWaitIntervals) //returns true if strlen(inbuf) > 0

{

if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)

{

sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;

intervalCount++;

Serial.printf("%s %d\n", waitstr, numWaitIntervals - intervalCount);

Serial1.printf("%s %d\r\n", waitstr, numWaitIntervals - intervalCount); //bluetooth

}

delay(250);

}

Serial.printf("Received %s from Serial, %s from Serial1\n", inbuf, inbuf1);

if (strncasecmp("Y", inbuf, 1) == 0 || strncasecmp("Y",inbuf1,1) == 0) //compare only 1st chars, as user input may have CR/LF appended

{

result = true;

}

return result;

}

bool GetUserInputStr0(char* inbuf)

{

//Purpose: Get user input from Serial0

//Inputs:

// inbuf = pointer to char[10] array to receive user input

//Outputs:

// inbuf = String object containing user input.

// returns True if user input was received, False if the routine timed out

//Plan:

// Wait for user input or timeout whichever occurs first

//Notes:

// 12/27/18 modified to work with both Serial & Serial1 ports. We assume that

// userinput is coming from one port or the other, but not both

// 01/02/19 re-written for cleaner code

//Serial1.printf("In GetUserInputStr0\n");

memset(inbuf, 0, BUFLEN);

int readbyte = 0;

int charidx = 0;

while (Serial.available() && charidx < 100)

{

readbyte = Serial.read();

inbuf[charidx] = readbyte;

charidx++;

}

if (strlen(inbuf) > 0)

{

Serial.print("Received "); Serial.print(inbuf); Serial.println(" from Serial0");

}

return (charidx < 100 && strlen(inbuf) > 0);

}

bool GetUserInputStr1(char* inbuf1)

{

//Purpose: Get user input from Serial1

//Inputs:

// inbuf1 = pointer to char[10] array to receive user input from Serial1

//Outputs:

// inbuf1 = String object containing user input from Serial1.

// returns True if user input was received, False if the routine timed out

//Plan:

// Wait for user input or timeout whichever occurs first

//Notes:

// 12/30/18 coped from GetUserInput & modified to work with Serial1 ports

// 01/02/19 re-written for cleaner code

//Serial1.printf("In GetUserInputStr1\n");

memset(inbuf1, 0, BUFLEN);

int readbyte = 0;

int charidx = 0;

while (Serial1.available() && charidx < 100)

{

readbyte = Serial1.read();

inbuf1[charidx] = readbyte;

charidx++;

}

if (strlen(inbuf1) > 0)

{

Serial1.print("Received "); Serial1.print(inbuf1); Serial1.println(" from Serial1");

}

return (charidx < 100 && strlen(inbuf1) > 0);

}

bool DoCalibration(int numwait_tare, int numwait_weight)

{

Serial.printf("Digital Scale Program\n");

Serial.printf("Program to automatically calibrate HX711/Load Cell to measure weight in Kg\n");

EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM

Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);

if (isnan((float)calibration_factor))

{

Serial.printf("invalid cal factor: Setting to -96650\n");

calibration_factor = -96650;

}

scale.set_scale(calibration_factor);

EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM

Serial.printf("The current stored tare offset factor is %li\n", tare_offset);

if (isnan((float)tare_offset))

{

Serial.printf("invalid cal factor: Setting to zero\n");

tare_offset = 0;

}

scale.set_offset(tare_offset);

//calibrate with known weights

Serial.println("HX711 Calibration");

Serial.println("Remove all non-fixture weight from scale, and press 't' to zero the scale");

Serial.println("Or any other character to skip this step");

Serial1.println("HX711 Calibration");

Serial1.println("Remove all non-fixture weight from scale, and press 't' to zero the scale");

Serial1.println("Or any other character to skip this step");

memset(inbuf, 0, BUFLEN);

memset(inbuf1, 0, BUFLEN);

int intervalCount = 0;

sinceLastWaitMsg = 0;

while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)

&& intervalCount < numwait_tare) //returns true if strlen(inbuf) > 0

{

if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)

{

sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;

intervalCount++;

Serial.printf("%s %d\n", waitstr, numwait_tare - intervalCount);

Serial1.printf("%s %d\r\n", waitstr, numwait_tare - intervalCount); //bluetooth

}

delay(250);

}

if (strncasecmp("T", inbuf, 1) == 0 || strncasecmp("T", inbuf1,1) == 0) //compare only 1st chars, as user input may have CR/LF appended

{

tare_offset = scale.read_average(); //Get a baseline reading

Serial.printf("Applying offset %li as tare adjustment\n", tare_offset);

scale.set_offset(tare_offset); //this value will be subtracted from all future measurements

Serial.printf("Writing offset %li to EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);

EEPROM_writeAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);

EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);

Serial.printf("Read offset %li from EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);

}

Serial.println("Apply a known weight (the higher the better) and enter its value in Kg");

Serial.println("Enter 0 to skip this step");

Serial1.println("Apply a known weight (the higher the better) and enter its value in Kg");

Serial1.println("Enter 0 to skip this step");

memset(inbuf, 0, BUFLEN);

memset(inbuf1, 0, BUFLEN);

intervalCount = 0;

sinceLastWaitMsg = 0;

while (!GetUserInputStr0(inbuf) && !GetUserInputStr1(inbuf1)

&& intervalCount < numwait_weight) //returns true if strlen(inbuf) > 0

{

if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)

{

sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;

intervalCount++;

Serial.printf("%s %d\n", waitstr, numwait_weight - intervalCount);

Serial1.printf("%s %d\r\n", waitstr, numwait_weight - intervalCount); //bluetooth

}

delay(250);

}

//calculate scale factor resulting in user-input wt

//wt(Kg) = (read_avg - OFFSET)/Scale

//Scale = (read_avg - OFFSET)/wt(Kg)

double wtKg = 0;

if (strlen(inbuf) > 0)

{

wtKg = atof(inbuf);

Serial.printf("User weight input was %4.2f\n", wtKg);

}

else if(strlen(inbuf1) > 0)

{

wtKg = atof(inbuf1);

Serial1.printf("User weight input was %4.2f\r\n", wtKg);

}

else

{

Serial.printf("No user input detected - using 0.00Kg\n");

Serial1.printf("No user input detected - using 0.00Kg\r\n");

}

long read_avg = scale.read_average();

long offset = scale.get_offset();

calibration_factor = (double)(read_avg - offset) / wtKg;

scale.set_scale(calibration_factor); //Adjust to this calibration factor

Serial.printf("User weight input was %4.2f, read_avg = %li, offset = %li, cal = ",

wtKg, read_avg, offset);

Serial.println(calibration_factor); //PrintEx won't print the cal factor value

Serial1.printf("User weight input was %4.2f, read_avg = %li, offset = %li, cal = ",

wtKg, read_avg, offset);

Serial1.println(calibration_factor); //PrintEx won't print the cal factor value

EEPROM_writeAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);

Serial.print("Wrote cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor

Serial.printf(" to EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);

Serial1.print("Wrote cal factor "); Serial1.print(calibration_factor); //Serial.printf doesn't work for cal factor

Serial1.printf(" to EEPROM address %d\r\n", CAL_FACTOR_EEPROM_ADDR);

EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);

Serial.print("Read cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor

Serial.printf(" from EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);

Serial1.print("Read cal factor "); Serial1.print(calibration_factor); //Serial.printf doesn't work for cal factor

Serial1.printf(" from EEPROM address %d\r\n", CAL_FACTOR_EEPROM_ADDR);

Serial.printf("\n\nCalibration Complete\n");

Serial1.printf("\n\nCalibration Complete\r\n");

return true;

}

Schematic:

Future Work:

Do some more work to reduce power consumption to extend the battery life. I got the ‘Snooze’ feature to work on the Teensy, but that only reduces the Teensy’s power consumption; it does nothing directly to reduce the power consumption of the other components. I tried using a MOSFET to turn the HC-05 BT module on & off, and found this to be impractical, as then the module loses its connection to the remote data collection device. I have also tried removing power from the LCD module, but that also turned out to be problematic.

Stay tuned,

Frank

Digital Tension Scale, Part IV

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Posted 25 December 2018

In my copious free time I have been refining the design for a low power battery operated tensionometer. In my last post on the subject, I had described the components I had planned to use, and in the ensuing weeks I have been working on implementing this design. There are several challenges in this project:

Bluetooth Link:

There are a huge number of Bluetooth products out there in the Maker-verse, with varying degrees of Arduino support, and widely varying performance characteristics. To add to the confusion, there is ‘regular’ Bluetooth and the more recent ‘BLE’ (Bluetooth Low Energy) which are completely incompatible with each other. As I now understand it, BLE is synonymous with Bluetooth 4.0+ (the iPhone 4S was the first smartphone to implement the new standard). However, the most common product in use in the Arduino world seems to be the venerable HC-05 ‘regular’ Bluetooth module, available from your local grocery store (well, not quite, but from almost everywhere else!) for not much more than a few pennies

I had no previous experience with BT modules, so this part of the project took some time, and was the last major part to be accomplished. After receiving my HC-05 modules from China, I used this tutorial to get started. The real challenge for this part of the project wasn’t getting the HC-05 hooked up to the microcontroller – it was sorting through all the layers of BT-related settings on my Win 10 laptop to pair with the HC-05 device and determine which serial port did what.

In Windows 10, I used the ‘Bluetooth and other devices settings’ panel (Settings -> Devices -> Bluetooth and other devices) to find and pair to the HC-05. The device shows up as ‘HC-05’ and the default pairing password is “1234”.
When the HC-05 is paired it automatically sets up at least two serial ports that show up in device manager as ‘Standard Serial over Bluetooth’ ports, as shown below. However, only one of these ports is actually usable for two-way communication, and it isn’t clear to me why, or how to tell which is which; I had to experiment with each available ‘SSoB’ port to figure out which to use (so far, it seems like the highest-numbered port is the proper one).
After the HC-05 is paired and the com ports are set up, then any serial terminal app (I used RealTerm) can be used to communicate between the PC and the microcontroller via the HC-05.
On the microcontroller (I used a Teensy 3.2 with multiple hardware serial ports), I wired the HC-05 to Serial1 leaving Serial (Serial0) available for normal communication between the Teensy and my Visual Studio 2017 Community Edition/Visual Micro add-on for Arduino development platform.

Physical Layout:

The original idea behind this project was to create a self-contained battery-operated digital weight scale that could display weight values on a local display, but could also stream the data live to a remote recording station like a laptop or smartphone. The ‘self-contained’ part requires that all the electronics be mounted on the S-shaped load cell assembly itself, and to that end I designed a housing that connects to the two bolts that hold the arms of the load cell. The idea is that all the electronics save the LCD display and the battery will be mounted to the underside of the box lid so that servicing would be easier. Also, by mounting everything to the lid, I can make cutouts for the charger and Teensy USB connectors for easy charging and reprogramming. After several iterations in TinkerCad, I came up with the following design

Looking up at the underside of the box lid, showing all modules except the battery and the LCD display

Showing the top of the lid with the mounting bracket for the load cell

Isometric view with transparent box walls. The LCD display module is under the battery. Note the cutouts for the charging and programming USB-C connections

Module Integration:

I had previously tested each module individually, but hadn’t had all of them working at the same time. I had tested the HC-05 with an Arduino Mega, and I had tested the load cell with both a Sparkfun Pro Micro and with a Teensy 3.2, and I had tested the Nokia LCD display with a Teensy 3.2, but I hadn’t put everything together. So I wired everything up on my half-size ASP plugboard and got it all working together with a simple program (included below) that exercised the LCD Display, the load cell, the BT module, and the battery charger, as shown in the following photos

RealTerm Serial Terminal Program showing load cell readouts collected wirelessly via the Bluetooth HC-05 modules

HC-05 Bluetooth, HX-711 Load Cell Amp, Sparkfun Charger, and Teensy Microcontroller modules integrated together. Note disconnected USB cable showing that the circuit is running on battery power. The scale is currently measuring 1.8 liters of water in the suspended plastic bag (note the ‘1.8 Kg’ reading on the LCD display)

Software:

The software used for the above integration tests is a reasonably complete sketch for day-to-day use of the digital weight scale. It displays the measured weight on the LCD display, and also sends it to the USB serial port for display on a directly connected PC, and to the HC-05 Bluetooth module for display/capture via a BT-connected laptop or smartphone. This program is shown below:

/*
    Name:       TeensyLowPowerDigitalScale.ino
    Created:	12/2/2018 9:43:43 PM
    Author:     FRANKWIN10\Frank
*/

#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_PCD8544.h>

#pragma region LOW_POWER_SUPP
//12/03/18 added for low power mode
#include <Snooze.h>
// Load just the 'timer' wake-up driver
SnoozeTimer timer;
SnoozeUSBSerial usb;
SnoozeBlock config_teensy32(usb, timer);
const int SLEEP_TIME_MSEC = 5000;
//const float INACTIVE_SCALE_THRESHOLD_KG = 1.f;
const float INACTIVE_SCALE_THRESHOLD_KG = -10.f;
//const int MIN_INACTIVE_SCALE_COUNT = 100;
const int MIN_INACTIVE_SCALE_COUNT = 20;
int numInactiveScaleCounts = 0;

#pragma endregion Low Power Support

#pragma region LOAD_CELL
#include "HX711.h"  //You must have this library in your arduino library folder
#include <EEPROM.h>
#include<EEPROMAnything.h> //so I can read the last calibration value from EEPROM
#define DOUT  A1
#define CLK  A0
HX711 scale(DOUT, CLK);

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands
long calibration_factor = -96650; //-106600 worked for my 40Kg max scale setup
long tare_offset = 0;
const int LED_PIN = 13;
const int CAL_FACTOR_EEPROM_ADDR = 0;
const int TARE_OFFSET_EEPROM_ADDR = CAL_FACTOR_EEPROM_ADDR + sizeof(calibration_factor);
float scaleKg = 0;
float vBatt = 0;
#pragma endregion Load Cell Support

#pragma region LCD_DISPLAY
// Hardware SPI (faster, but must use certain hardware pins):
// Note with hardware SPI MISO and SS pins aren't used but will still be read
// and written to during SPI transfer.  Be careful sharing these pins!
// SCK is LCD serial clock (SCLK) - this is pin 13 on Arduino Uno
// MOSI is LCD DIN - this is pin 11 on an Arduino Uno
// pin 6 - Data/Command select (D/C)
// pin 5 - LCD chip select (CS)
// pin 4 - LCD reset (RST)
const int LCD_DC_PIN = 6;
const int LCD_CS_PIN = 5;
const int LCD_RST_PIN = 4;
const int SPI_DOUT_PIN = 11;
const int SPI_SCK_PIN = A0;

//Adafruit_PCD8544 display = Adafruit_PCD8544(6, 5, 4);//11/25/18
Adafruit_PCD8544 display = Adafruit_PCD8544(LCD_DC_PIN, LCD_CS_PIN, LCD_RST_PIN);//12/16/18 chg to identifiers
#pragma endregion Noki LCD Display

#pragma region BATT_FUEL_GUAGE
const int BATT_SYMBOL_X = 68;
const int BATT_SYMBOL_Y = 1;
const int BATT_SYMBOL_H = 8;
const int BATT_SYMBOL_W = 16;
const int DEFAULT_CHAR_HEIGHT = 8;
const int DEFAULT_CHAR_WIDTH = 5;
const int DEFAULT_CHAR_SIZE = 2;

//added 12/03/18 for battV measurements
//12/06/18 changed to internal 1.2V reference and 30K:10K divider
const int DEAD_BATT_COUNTS = 642;
const int FULL_BATT_COUNTS = 887;
const float FULL_BATT_VOLTS = 4.2;
const float DEAD_BATT_VOLTS = 3.0;
const float VOLTS_PER_COUNT = (FULL_BATT_VOLTS - DEAD_BATT_VOLTS) / (FULL_BATT_COUNTS - DEAD_BATT_COUNTS);
#pragma endregion Battery Fuel Guage



void setup() 
{
	Serial.begin(115200);
	delay(1000); //need this to get serial printout

	Serial.println("Welcome to the Teensy Low Power Digital Scale Program");

	Serial1.begin(9600);
	Serial1.println("Welcome via Bluetooth!");


	/********************************************************
	 Set Low Power Timer wake up in milliseconds.
	 ********************************************************/
	timer.setTimer(SLEEP_TIME_MSEC);// milliseconds

	//12/04/18 added code to set analog reference to internal 1.2V source
	analogReference(INTERNAL1V1);

	//initialize load cell and retrieve cal/tar values from EEPROM
	EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM
	Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);
	scale.set_scale(calibration_factor);

	EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM
	Serial.printf("The current stored tare offset factor is %li\n", tare_offset);
	scale.set_offset(tare_offset);

	//initialize LCD display
	display.begin();
	display.setContrast(60); //pretty dark
	display.setTextSize(1);
	display.setTextColor(BLACK);
	display.setCursor(0, 0);

	display.display(); //first time - shows the Adafruit logo
	delay(1000); //show Adafruit logo for 1 sec
	display.clearDisplay();   // clears the screen and buffer
	display.display(); //first time - shows the Adafruit logo

	////initial battery and scale reading
	//vBatt = UpdateBatteryDisplay();
	//scaleKg = UpdateScaleDisplay();
	//display.display();
}


void loop()
{
	//12/06/18 now using 30K/10K voltage divider on A7 and 1.2V ref.
	display.clearDisplay(); //clear memory bitmap
	display.setCursor(0, 0);
	vBatt = UpdateBatteryDisplay();
	//scaleKg = UpdateScaleDisplay();
	scaleKg = scale.get_units(3);
	Serial1.printf("%5.3f\n\r", scaleKg); //to BT module
	Serial.printf("%5.3f\n", scaleKg); //to serial console
	display.print(scaleKg); display.println(" Kg");//to LCD display
	display.display();


	//if the scale has been quiet for a while, go to sleep
	if (scaleKg <= INACTIVE_SCALE_THRESHOLD_KG)
	{
		numInactiveScaleCounts++;
		if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)
		{
			numInactiveScaleCounts = MIN_INACTIVE_SCALE_COUNT;
		}
		//numInactiveScaleCounts = (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT) ? 
		//	MIN_INACTIVE_SCALE_COUNT : numInactiveScaleCounts++;
		//display.display();
	}
	else
	{
		numInactiveScaleCounts = 0; //one active measurment wakes everything up
		//vBatt = UpdateBatteryDisplay();
		//scaleKg = UpdateScaleDisplay();
		//display.display();
	}

	if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)
	{
		Serial.printf("Going to sleep at %li mSec\n", millis());
		//numInactiveScaleCounts = 0; //this should cause system to stay awake for a second or so
		display.clearDisplay();
		display.display();
		Snooze.sleep(config_teensy32); //sleep
	}

	delay(100);
}

float UpdateScaleDisplay()
{
	float kG = scale.get_units(3);
	//float kG = (float)random(0,40);
	display.print(kG); display.println(" Kg");
	return kG;
}

float UpdateBatteryDisplay()
{
	int batt_counts = analogRead(A9);
	float batt_volts = DEAD_BATT_VOLTS + (batt_counts - DEAD_BATT_COUNTS) * VOLTS_PER_COUNT;
	display.print(batt_volts); display.println(" V");
	UpdateBatterySymbol(batt_volts);
	return batt_volts;
}


void UpdateBatterySymbol(float vbatt)
{
	//Purpose: Update the battery symbol to show current charge state
	//Inputs: 
	//	vbatt = current battery voltage
	//	FULL_BATT_VOLTS = fully charged battery voltage
	//	DEAD_BATT_VOLTS = fully discharged battery voltage
	//	BATT_SYMBOL_X/Y/H/W = battery symbol loc/dims
	//Outputs: Updated battery symbol
	//Plan:
	//	Step1: draw open rect for battery symbol outline
	//	Step2: draw filled rect indicating charge state
	//	Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

//Step1: draw open rect for battery symbol outline
	display.drawRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, BATT_SYMBOL_W, BATT_SYMBOL_H, 1);

	//Step2: draw filled rect indicating charge state
	float Vrange = FULL_BATT_VOLTS - DEAD_BATT_VOLTS;
	int fillWidth = (int)(BATT_SYMBOL_W * ((vbatt - DEAD_BATT_VOLTS) / Vrange) + 0.5f);
	//Serial.printf("vbat, fillW = %4.2f,%d\n", vbatt, fillWidth);
	display.fillRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, fillWidth, BATT_SYMBOL_H, 1);

	//Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol
	if (vbatt <= DEAD_BATT_VOLTS)
	{
		//try drawing lines from corner to corner
		int ulX = BATT_SYMBOL_X;
		int ulY = BATT_SYMBOL_Y;
		int urX = BATT_SYMBOL_X + BATT_SYMBOL_W;
		int urY = ulY;
		int lrX = urX;
		int lrY = urY + BATT_SYMBOL_H;
		int llX = ulX;
		int llY = lrY;

		display.drawLine(ulX, ulY, lrX, lrY, 1);
		display.drawLine(llX, llY, urX, urY, 1);
	}
}

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Name: TeensyLowPowerDigitalScale.ino

Created: 12/2/2018 9:43:43 PM

Author: FRANKWIN10\Frank

#include <SPI.h>

#include <Adafruit_GFX.h>

#include <Adafruit_PCD8544.h>

#pragma region LOW_POWER_SUPP

//12/03/18 added for low power mode

#include <Snooze.h>

// Load just the 'timer' wake-up driver

SnoozeTimer timer;

SnoozeUSBSerial usb;

SnoozeBlock config_teensy32(usb, timer);

const int SLEEP_TIME_MSEC = 5000;

//const float INACTIVE_SCALE_THRESHOLD_KG = 1.f;

const float INACTIVE_SCALE_THRESHOLD_KG = -10.f;

//const int MIN_INACTIVE_SCALE_COUNT = 100;

const int MIN_INACTIVE_SCALE_COUNT = 20;

int numInactiveScaleCounts = 0;

#pragma endregion Low Power Support

#pragma region LOAD_CELL

#include "HX711.h" //You must have this library in your arduino library folder

#include <EEPROM.h>

#include<EEPROMAnything.h> //so I can read the last calibration value from EEPROM

#define DOUT A1

#define CLK A0

HX711 scale(DOUT, CLK);

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands

long calibration_factor = -96650; //-106600 worked for my 40Kg max scale setup

long tare_offset = 0;

const int LED_PIN = 13;

const int CAL_FACTOR_EEPROM_ADDR = 0;

const int TARE_OFFSET_EEPROM_ADDR = CAL_FACTOR_EEPROM_ADDR + sizeof(calibration_factor);

float scaleKg = 0;

float vBatt = 0;

#pragma endregion Load Cell Support

#pragma region LCD_DISPLAY

// Hardware SPI (faster, but must use certain hardware pins):

// Note with hardware SPI MISO and SS pins aren't used but will still be read

// and written to during SPI transfer. Be careful sharing these pins!

// SCK is LCD serial clock (SCLK) - this is pin 13 on Arduino Uno

// MOSI is LCD DIN - this is pin 11 on an Arduino Uno

// pin 6 - Data/Command select (D/C)

// pin 5 - LCD chip select (CS)

// pin 4 - LCD reset (RST)

const int LCD_DC_PIN = 6;

const int LCD_CS_PIN = 5;

const int LCD_RST_PIN = 4;

const int SPI_DOUT_PIN = 11;

const int SPI_SCK_PIN = A0;

//Adafruit_PCD8544 display = Adafruit_PCD8544(6, 5, 4);//11/25/18

Adafruit_PCD8544 display = Adafruit_PCD8544(LCD_DC_PIN, LCD_CS_PIN, LCD_RST_PIN);//12/16/18 chg to identifiers

#pragma endregion Noki LCD Display

#pragma region BATT_FUEL_GUAGE

const int BATT_SYMBOL_X = 68;

const int BATT_SYMBOL_Y = 1;

const int BATT_SYMBOL_H = 8;

const int BATT_SYMBOL_W = 16;

const int DEFAULT_CHAR_HEIGHT = 8;

const int DEFAULT_CHAR_WIDTH = 5;

const int DEFAULT_CHAR_SIZE = 2;

//added 12/03/18 for battV measurements

//12/06/18 changed to internal 1.2V reference and 30K:10K divider

const int DEAD_BATT_COUNTS = 642;

const int FULL_BATT_COUNTS = 887;

const float FULL_BATT_VOLTS = 4.2;

const float DEAD_BATT_VOLTS = 3.0;

const float VOLTS_PER_COUNT = (FULL_BATT_VOLTS - DEAD_BATT_VOLTS) / (FULL_BATT_COUNTS - DEAD_BATT_COUNTS);

#pragma endregion Battery Fuel Guage

void setup()

{

Serial.begin(115200);

delay(1000); //need this to get serial printout

Serial.println("Welcome to the Teensy Low Power Digital Scale Program");

Serial1.begin(9600);

Serial1.println("Welcome via Bluetooth!");

/********************************************************

Set Low Power Timer wake up in milliseconds.

********************************************************/

timer.setTimer(SLEEP_TIME_MSEC);// milliseconds

//12/04/18 added code to set analog reference to internal 1.2V source

analogReference(INTERNAL1V1);

//initialize load cell and retrieve cal/tar values from EEPROM

EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM

Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);

scale.set_scale(calibration_factor);

EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM

Serial.printf("The current stored tare offset factor is %li\n", tare_offset);

scale.set_offset(tare_offset);

//initialize LCD display

display.begin();

display.setContrast(60); //pretty dark

display.setTextSize(1);

display.setTextColor(BLACK);

display.setCursor(0, 0);

display.display(); //first time - shows the Adafruit logo

delay(1000); //show Adafruit logo for 1 sec

display.clearDisplay(); // clears the screen and buffer

display.display(); //first time - shows the Adafruit logo

////initial battery and scale reading

//vBatt = UpdateBatteryDisplay();

//scaleKg = UpdateScaleDisplay();

//display.display();

}

void loop()

{

//12/06/18 now using 30K/10K voltage divider on A7 and 1.2V ref.

display.clearDisplay(); //clear memory bitmap

display.setCursor(0, 0);

vBatt = UpdateBatteryDisplay();

//scaleKg = UpdateScaleDisplay();

scaleKg = scale.get_units(3);

Serial1.printf("%5.3f\n\r", scaleKg); //to BT module

Serial.printf("%5.3f\n", scaleKg); //to serial console

display.print(scaleKg); display.println(" Kg");//to LCD display

display.display();

//if the scale has been quiet for a while, go to sleep

if (scaleKg <= INACTIVE_SCALE_THRESHOLD_KG)

{

numInactiveScaleCounts++;

if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)

{

numInactiveScaleCounts = MIN_INACTIVE_SCALE_COUNT;

}

//numInactiveScaleCounts = (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT) ?

// MIN_INACTIVE_SCALE_COUNT : numInactiveScaleCounts++;

//display.display();

}

else

{

numInactiveScaleCounts = 0; //one active measurment wakes everything up

//vBatt = UpdateBatteryDisplay();

//scaleKg = UpdateScaleDisplay();

//display.display();

}

if (numInactiveScaleCounts >= MIN_INACTIVE_SCALE_COUNT)

{

Serial.printf("Going to sleep at %li mSec\n", millis());

//numInactiveScaleCounts = 0; //this should cause system to stay awake for a second or so

display.clearDisplay();

display.display();

Snooze.sleep(config_teensy32); //sleep

}

delay(100);

}

float UpdateScaleDisplay()

{

float kG = scale.get_units(3);

//float kG = (float)random(0,40);

display.print(kG); display.println(" Kg");

return kG;

}

float UpdateBatteryDisplay()

{

int batt_counts = analogRead(A9);

float batt_volts = DEAD_BATT_VOLTS + (batt_counts - DEAD_BATT_COUNTS) * VOLTS_PER_COUNT;

display.print(batt_volts); display.println(" V");

UpdateBatterySymbol(batt_volts);

return batt_volts;

}

void UpdateBatterySymbol(float vbatt)

{

//Purpose: Update the battery symbol to show current charge state

//Inputs:

// vbatt = current battery voltage

// FULL_BATT_VOLTS = fully charged battery voltage

// DEAD_BATT_VOLTS = fully discharged battery voltage

// BATT_SYMBOL_X/Y/H/W = battery symbol loc/dims

//Outputs: Updated battery symbol

//Plan:

// Step1: draw open rect for battery symbol outline

// Step2: draw filled rect indicating charge state

// Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

//Step1: draw open rect for battery symbol outline

display.drawRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, BATT_SYMBOL_W, BATT_SYMBOL_H, 1);

//Step2: draw filled rect indicating charge state

float Vrange = FULL_BATT_VOLTS - DEAD_BATT_VOLTS;

int fillWidth = (int)(BATT_SYMBOL_W * ((vbatt - DEAD_BATT_VOLTS) / Vrange) + 0.5f);

//Serial.printf("vbat, fillW = %4.2f,%d\n", vbatt, fillWidth);

display.fillRect(BATT_SYMBOL_X, BATT_SYMBOL_Y, fillWidth, BATT_SYMBOL_H, 1);

//Step3: If vbatt <= DEAD_BATT_VOLTS, draw 'X' over symbol

if (vbatt <= DEAD_BATT_VOLTS)

{

//try drawing lines from corner to corner

int ulX = BATT_SYMBOL_X;

int ulY = BATT_SYMBOL_Y;

int urX = BATT_SYMBOL_X + BATT_SYMBOL_W;

int urY = ulY;

int lrX = urX;

int lrY = urY + BATT_SYMBOL_H;

int llX = ulX;

int llY = lrY;

display.drawLine(ulX, ulY, lrX, lrY, 1);

display.drawLine(llX, llY, urX, urY, 1);

}

However, this program depends on the proper calibration of the load cell, which I have been doing with a separate sketch (also included below):

/*
    Name:       TeensyDigitalScaleCalibration.ino
    Created:	12/11/2018 8:47:58 PM
    Author:     FRANKWIN10\Frank
*/


/*
	Name:       DigitalScaleAutoCal.ino
	Created:	11/15/2018 4:49:12 PM
	Author:     FRANKWIN10\Frank

	This program is a modification of the November 2016 circuits4you.com program for interfacing
	with the HX711 Module coupled with a typical load cell.  It's purpose is to automatically
	calibrate the combination to accurately display weight in Kg.
	The process is as follows:
	Step1:	User opts to calibrate by entering 'Y' at the prompt.  Entering any other key (or
			just letting the question time out) will skip the calibration process
	Step2:  User establishes 'tare' weight physical configuration with any non-measured weight
			attached (in my case, the bucket used to hold measured amounts of water used for
			weight calibration), and then presses 'T' to zero out the 'tare weight'
	Step3:	The user establishes a calibration weight condition (in my case, 1.8 liters of water)
			and enters the weight value (in Kg).  The program then calculates the scale factor
			needed to calibrate the scale for the entered weight and then automatically
			drops into measurement mode
	Step5:	The user enters 'q' to quit measurements.

*/

/*
 * circuits4you.com
 * 2016 November 25
 * Load Cell HX711 Module Interface with Arduino to measure weight in Kgs
 Arduino
 pin
 2 -> HX711 CLK
 3 -> DOUT
 5V -> VCC
 GND -> GND

 Most any pin on the Arduino Uno will be compatible with DOUT/CLK.
 The HX711 board can be powered from 2.7V to 5V so the Arduino 5V power should be fine.
*/

#include "HX711.h"  //You must have this library in your arduino library folder
#include <EEPROM.h>
#include<EEPROMAnything.h> //so I can store the last calibration value in EEPROM
#include <elapsedMillis.h>

elapsedMillis sinceLastWaitMsg;
const int WAITINGMSGINTERVALMSEC = 1000; //1-sec intervals
const int MAX_WAITING_INTERVALS = 10; //how long to wait before starting measurement
int numWaitIntervals = 0;
char inbuf[20]; //buffer for user input 

#define DOUT  A1
#define CLK  A0

HX711 scale(DOUT, CLK);

//Change this calibration factor as per your load cell once it is found. You many need to vary it in thousands
long calibration_factor = -96650; //-106600 worked for my 40Kg max scale setup
long tare_offset = 0;
bool bDoneMeasuring = false;
const int LED_PIN = 13;
const char* waitstr = "Waiting...Measurements will start in ";
const int CAL_FACTOR_EEPROM_ADDR = 0;
const int TARE_OFFSET_EEPROM_ADDR = CAL_FACTOR_EEPROM_ADDR + sizeof(calibration_factor);

void setup()
{
	delay(2000); //required to wait for Pro Micro to switch from programming to output serial port assignments
	Serial.begin(115200);

	pinMode(LED_BUILTIN, OUTPUT);

	memset(inbuf, 0, sizeof(inbuf));


	Serial.printf("Digital Scale Program\n");
	Serial.printf("Program to automatically calibrate HX711/Load Cell to measure weight in Kg\n");

	EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor); //read current cal scale from EEPROM
	Serial.printf("The current stored scale calibration factor is %li\n", calibration_factor);

	if (isnan((float)calibration_factor))
	{
		Serial.printf("invalid cal factor:  Setting to -96650\n");
		calibration_factor = -96650;
	}
	scale.set_scale(calibration_factor);


	EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset); //read current tare offset from EEPROM
	Serial.printf("The current stored tare offset factor is %li\n", tare_offset);

	if (isnan((float)tare_offset))
	{
		Serial.printf("invalid cal factor:  Setting to zero\n");
		tare_offset = 0;
	}
	scale.set_offset(tare_offset);

	Serial.printf("Enter 'Y' to start the calibration, any other key to skip\n");
	Serial.printf("Calibrate (Y/N) (Y)?\n");

	if (GetUserInputStr(inbuf, 5)) //returns true if strlen(inbuf) > 0
	{
		Serial.printf("\nReceived "); Serial.print(inbuf); Serial.println(" from user");

		if (strncasecmp("Y", inbuf, 1) == 0) //compare only 1st chars, as user input may have CR/LF appended
		{
			//calibrate with known weights
			Serial.println("HX711 Calibration");
			Serial.println("Remove all non-fixture weight from scale, and press 't' to zero the scale");
			Serial.println("Or any other character to skip this step");

			memset(inbuf, 0, sizeof(inbuf));
			if (GetUserInputStr(inbuf, 10)) //returns true if strlen(inbuf) > 0
			{
				Serial.printf("\nReceived "); Serial.print(inbuf); Serial.println(" from user");

				if (strncasecmp("T", inbuf, 1) == 0) //compare only 1st chars, as user input may have CR/LF appended
				{
					tare_offset = scale.read_average(); //Get a baseline reading
					Serial.printf("Applying offset %li as tare adjustment\n", tare_offset);
					scale.set_offset(tare_offset); //this value will be subtracted from all future measurements
					Serial.printf("Writing offset %li to EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);
					EEPROM_writeAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);

					EEPROM_readAnything(TARE_OFFSET_EEPROM_ADDR, tare_offset);
					Serial.printf("Read offset %li from EEPROM address %d\n", tare_offset, TARE_OFFSET_EEPROM_ADDR);
				}
			}

			Serial.println("Apply a known weight (the higher the better) and enter its value in Kg");
			Serial.println("Enter 0 to skip this step");

			memset(inbuf, 0, sizeof(inbuf));
			if (GetUserInputStr(inbuf, 30)) //returns true if strlen(inbuf) > 0
			{
				Serial.printf("\nReceived "); Serial.print(inbuf); Serial.println(" from user");

				//calculate scale factor resulting in user-input wt
				//wt(Kg) = (read_avg - OFFSET)/Scale
				//Scale = (read_avg - OFFSET)/wt(Kg)
				double wtKg = atof(inbuf);
				Serial.printf("User weight input was %4.2f\n", wtKg);
				long read_avg = scale.read_average();
				long offset = scale.get_offset();
				calibration_factor = (double)(read_avg - offset) / wtKg;
				scale.set_scale(calibration_factor); //Adjust to this calibration factor

				Serial.printf("User weight input was %4.2f, read_avg = %li, offset = %li, cal = ",
					wtKg, read_avg, offset);
				Serial.println(calibration_factor); //PrintEx won't print the cal factor value


				EEPROM_writeAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);
				Serial.print("Wrote cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor
				Serial.printf(" to EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);


				EEPROM_readAnything(CAL_FACTOR_EEPROM_ADDR, calibration_factor);
				Serial.print("Read cal factor "); Serial.print(calibration_factor); //Serial.printf doesn't work for cal factor
				Serial.printf(" from EEPROM address %d\n", CAL_FACTOR_EEPROM_ADDR);
			}
		}
	}

	Serial.printf("\n\nCalibration Complete... Starting Measurements\n\n");
	Serial.printf("\nTo quit measuring, enter 'Q'\n");
	Serial.printf("Time(mSec)\tWt(Kg)\n");

	bDoneMeasuring = false;
	while (!bDoneMeasuring)
	{

		Serial.printf("%lu\t%3.2f\n", millis(), scale.get_units(3));
		delay(250);

		if (Serial.available())
		{
			char temp = Serial.read();
			Serial.printf("got %c\n", temp);
			if (temp == 'q')
			{
				bDoneMeasuring = true; //all done
			}
		}
	}

	Serial.printf("Measurements Completed - Have a nice day!\n");
}

void loop()
{
}


bool GetUserInputStr(char* inbuf, int numWaitIntervals)
{
	//Purpose: Get user input
	//Inputs:
	//	inbuf = pointer to char[10] array to receive user input
	//Outputs:
	//	inbuf = String object containing user input. If inbuf.length() == 0, then the routine timed out
	//	returns True if user input was received, False if the routine timed out
	//Plan:
	//	Wait for user input or timeout whichever occurs first
	int intervalCount = 0;
	while (strlen(inbuf) <= 0 && intervalCount < numWaitIntervals)
	{
		Serial.readBytesUntil('\n', inbuf, 10);

		if (sinceLastWaitMsg >= WAITINGMSGINTERVALMSEC)
		{
			sinceLastWaitMsg -= WAITINGMSGINTERVALMSEC;
			intervalCount++;
			Serial.printf("%s %d\n", waitstr, numWaitIntervals - intervalCount);
		}
		delay(250);
	}

	return (strlen(inbuf) > 0);
}

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Name: TeensyDigitalScaleCalibration.ino

Created: 12/11/2018 8:47:58 PM