Monthly Archives: June 2026

2 Wheel Robot with Vision Processing, Part III

07 July 2026 Update: Wrapping up the Wifi_OTA Demo project

This little project had more than its share of bumps and bruises, but I think Grok Code and I have finally got it done. The project has four major parts; three on my PC and one on the pi5.

The Wifi_OTA Visual Studio/Visual Micro project on my PC
A ‘board.txt’ file in the same folder as the Wifi_OTA project. This file tells VS what to do after the build step
A small Python script that copies the .HEX output from the compile to the ‘latest.hex’ file on the pi5
A Python program on the pi5 that watches for updates to ‘latest.hex’ and when one is detected, passes that along the the teensy on its Serial1 port

Here is the Wifi_OTA.ino file: All it does is blink the built-in LED a couple of times and then waits for a ‘U’ character to start the flash update process.

// Generated on: 2026-06-17 14:30:00 UTC
// Wifi_OTA.ino - UART OTA Test via Pi5 Serial1

#include "FXUtil.h"
extern "C"
{
#include "FlashTxx.h"
}

//#define USING_HC05

//needed for compile-time switching
char c;
uint32_t buffer_addr, buffer_size;

#define BLINK_TIME_MSEC 200

void setup()
{
  Serial.begin(115200);      // USB debug port
  delay(2000);
  Serial.println("\nTo USB: === Wifi_OTA - Teensy Ready ===");
  Serial.println("To USB: Send 'U' from TeraTerm on Serial2 or Pi5 on Serial1 to trigger OTA update");

#ifdef USING_HC05
  Serial2.begin(115200);     // UART to HC05
  delay(2000);
  Serial2.println("\nTo TeraTerm: === Wifi_OTA - Teensy Ready ===");
  Serial2.println("To TeraTerm: Send 'U' from TeraTerm on Serial2 to trigger OTA update");
#else
  Serial1.begin(115200);     // UART to Pi5
  Serial1.println("\nTo Pi5: === Wifi_OTA - Teensy Ready ===");
  Serial1.println("To Pi5: Send 'U' from Pi5 on Serial1 to trigger OTA update");
  Serial1.flush();

#endif
  pinMode(LED_BUILTIN, OUTPUT);

  //07/02/26 revised for more definitive successful update indication
  digitalWrite(LED_BUILTIN, HIGH);
  delay(BLINK_TIME_MSEC);

  digitalWrite(LED_BUILTIN, LOW);
  delay(BLINK_TIME_MSEC);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(BLINK_TIME_MSEC);

  digitalWrite(LED_BUILTIN, LOW);
  delay(BLINK_TIME_MSEC);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(BLINK_TIME_MSEC);
}

void loop()
{
#ifdef USING_HC05

  if (Serial2.available())
  {
    c = Serial2.read();
    Serial2.printf("Received %c on Serial2: '\n", c);

    if (c == 'U' || c == 'u')
    {
      Serial2.println("\nStart Program Update - Send new HEX file!");
      digitalWrite(LED_BUILTIN, LOW);   // visual feedback
      delay(500);

      //uint32_t buffer_addr, buffer_size;
      if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)
      {
        Serial2.println("Failed to init buffer");
        digitalWrite(LED_BUILTIN, HIGH);
        return;
      }

      Serial2.println("Calling update_firmware() on Serial2...");
      while (Serial2.available()) Serial2.read(); // clear buffer
      update_firmware(&Serial2, &Serial2, buffer_addr, buffer_size);
    }
#else
  if (Serial1.available())
  {
    c = Serial1.read();
    Serial1.printf("Received %c on Serial1: '\n", c);
    Serial1.print(c);
  }
  if (c == 'U' || c == 'u')
  {
    Serial.println("\nStart Program Update - Send new HEX file!");
    digitalWrite(LED_BUILTIN, LOW);   // visual feedback
    delay(500);

    //uint32_t buffer_addr, buffer_size;
    if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)
    {
      Serial.println("Failed to init buffer");
      digitalWrite(LED_BUILTIN, HIGH);
      return;
    }

    while (Serial1.available()) Serial1.read(); // clear buffer

    Serial.println("Calling update_firmware() on Serial1...");
    update_firmware(&Serial1, &Serial1, buffer_addr, buffer_size);
#endif

    //firmware_buffer_free(buffer_addr, buffer_size);
#ifdef USING_HC05
    Serial2.println("after update_firmware");
    firmware_buffer_free(buffer_addr, buffer_size);
    Serial2.println("Firmware update call completed. About to REBOOT...");
#else
    Serial.println("update_firmware() returned - freeing buffer");
    firmware_buffer_free(buffer_addr, buffer_size);
    Serial.println("Firmware update call completed. About to REBOOT...");
#endif
    delay(2000);  // Give time for the message to be sent

    REBOOT;
  }
  }

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// Generated on: 2026-06-17 14:30:00 UTC

// Wifi_OTA.ino - UART OTA Test via Pi5 Serial1

#include "FXUtil.h"

extern "C"

{

#include "FlashTxx.h"

}

//#define USING_HC05

//needed for compile-time switching

char c;

uint32_t buffer_addr, buffer_size;

#define BLINK_TIME_MSEC 200

void setup()

{

Serial.begin(115200); // USB debug port

delay(2000);

Serial.println("\nTo USB: === Wifi_OTA - Teensy Ready ===");

Serial.println("To USB: Send 'U' from TeraTerm on Serial2 or Pi5 on Serial1 to trigger OTA update");

#ifdef USING_HC05

Serial2.begin(115200); // UART to HC05

delay(2000);

Serial2.println("\nTo TeraTerm: === Wifi_OTA - Teensy Ready ===");

Serial2.println("To TeraTerm: Send 'U' from TeraTerm on Serial2 to trigger OTA update");

#else

Serial1.begin(115200); // UART to Pi5

Serial1.println("\nTo Pi5: === Wifi_OTA - Teensy Ready ===");

Serial1.println("To Pi5: Send 'U' from Pi5 on Serial1 to trigger OTA update");

Serial1.flush();

#endif

pinMode(LED_BUILTIN, OUTPUT);

//07/02/26 revised for more definitive successful update indication

digitalWrite(LED_BUILTIN, HIGH);

delay(BLINK_TIME_MSEC);

digitalWrite(LED_BUILTIN, LOW);

delay(BLINK_TIME_MSEC);

digitalWrite(LED_BUILTIN, HIGH);

delay(BLINK_TIME_MSEC);

digitalWrite(LED_BUILTIN, LOW);

delay(BLINK_TIME_MSEC);

digitalWrite(LED_BUILTIN, HIGH);

delay(BLINK_TIME_MSEC);

}

void loop()

{

#ifdef USING_HC05

if (Serial2.available())

{

c = Serial2.read();

Serial2.printf("Received %c on Serial2: '\n", c);

if (c == 'U' || c == 'u')

{

Serial2.println("\nStart Program Update - Send new HEX file!");

digitalWrite(LED_BUILTIN, LOW); // visual feedback

delay(500);

//uint32_t buffer_addr, buffer_size;

if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)

{

Serial2.println("Failed to init buffer");

digitalWrite(LED_BUILTIN, HIGH);

return;

}

Serial2.println("Calling update_firmware() on Serial2...");

while (Serial2.available()) Serial2.read(); // clear buffer

update_firmware(&Serial2, &Serial2, buffer_addr, buffer_size);

}

#else

if (Serial1.available())

{

c = Serial1.read();

Serial1.printf("Received %c on Serial1: '\n", c);

Serial1.print(c);

}

if (c == 'U' || c == 'u')

{

Serial.println("\nStart Program Update - Send new HEX file!");

digitalWrite(LED_BUILTIN, LOW); // visual feedback

delay(500);

//uint32_t buffer_addr, buffer_size;

if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)

{

Serial.println("Failed to init buffer");

digitalWrite(LED_BUILTIN, HIGH);

return;

}

while (Serial1.available()) Serial1.read(); // clear buffer

Serial.println("Calling update_firmware() on Serial1...");

update_firmware(&Serial1, &Serial1, buffer_addr, buffer_size);

#endif

//firmware_buffer_free(buffer_addr, buffer_size);

#ifdef USING_HC05

Serial2.println("after update_firmware");

firmware_buffer_free(buffer_addr, buffer_size);

Serial2.println("Firmware update call completed. About to REBOOT...");

#else

Serial.println("update_firmware() returned - freeing buffer");

firmware_buffer_free(buffer_addr, buffer_size);

Serial.println("Firmware update call completed. About to REBOOT...");

#endif

delay(2000); // Give time for the message to be sent

REBOOT;

}

Here is the ‘board.txt’ file that calls the PostBuild.py program when an F5 debug compile is completed:

#Updated 06/27/26 Post-Build: Copy .hex to Pi5
recipe.hooks.deploy.preupload.1.pattern=python "C:\Users\Frank\Documents\Robot_Projects\my_vision_robot\software\Wifi_OTA\teensy\Wifi_OTA\PostBuild_OTA.py" "{vm.runtime.build.final_output_path}" "{build.project_name}" "{build.project_path}" "{vm.runtime.build.intermediate_output_path}"
recipe.hooks.deploy.preupload.1.use_shell_execute=true

#Updated 06/27/26 Post-Build: Copy .hex to Pi5

recipe.hooks.deploy.preupload.1.pattern=python "C:\Users\Frank\Documents\Robot_Projects\my_vision_robot\software\Wifi_OTA\teensy\Wifi_OTA\PostBuild_OTA.py" "{vm.runtime.build.final_output_path}" "{build.project_name}" "{build.project_path}" "{vm.runtime.build.intermediate_output_path}"

recipe.hooks.deploy.preupload.1.use_shell_execute=true

And here is the Python script that copies the .HEX output from the compiler over to ‘latest.hex’ on the pi5:

#!/usr/bin/env python3
"""
Post-Build OTA Helper for Visual Micro
"""

import sys
import os
import subprocess
from datetime import datetime

# ============== CONFIGURATION ==============
VERBOSE = False         # Set to True only when debugging
# ===========================================

def main():
    print("\n" + "="*60)
    print("Post-Build OTA Transfer to Pi5")
    print("="*60)

    if VERBOSE:
        print("\n=== Visual Micro Path Variables ===")
        print(f"build.project_path              = {sys.argv[3] if len(sys.argv) > 3 else 'Not provided'}")
        print(f"vm.runtime.build.intermediate_output_path = {sys.argv[4] if len(sys.argv) > 4 else 'Not provided'}")
        print(f"vm.runtime.build.final_output_path = {sys.argv[1] if len(sys.argv) > 1 else 'Not provided'}")
        print("="*40)

    if len(sys.argv) < 4:
        print("ERROR: Not enough arguments provided.")
        input("Press Enter to close...")
        sys.exit(1)

    intermediate_path = sys.argv[4].rstrip('\\')
    project_name = sys.argv[2] if len(sys.argv) > 2 else "Unknown"
    #hex_path = f"{intermediate_path}\\Wifi_OTA_Demo.hex"
    hex_path = f"{intermediate_path}\\Wifi_OTA.hex"

    if VERBOSE:
        print("\n=== Derived File Paths ===")
        print(f"Project Name     : {project_name}")
        print(f"Intermediate Dir : {intermediate_path}")
        print(f"Hex File Path    : {hex_path}")
        print("="*40)
        print(f"Time : {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

    if not os.path.exists(hex_path):
        print(f"ERROR: Hex file not found: {hex_path}")
        input("Press Enter to close...")
        sys.exit(1)

    print("\nCopying .hex to Pi5...")
    
    try:
        #subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/firmware/latest.hex"], 
        #               capture_output=True, text=True, check=True)
        subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/latest.hex"], 
                       capture_output=True, text=True, check=True)

        print("SUCCESS: .hex file copied to Pi5.")
    except subprocess.CalledProcessError:
        print("\nERROR: Failed to copy .hex file to Pi5.")
        if VERBOSE:
            print("Check that the Pi5 is reachable and scp is set up.")
        sys.exit(1)
    except FileNotFoundError:
        print("\nERROR: 'scp' command not found. Is OpenSSH installed?")
        sys.exit(1)

    print(f"\nPost-build completed at {datetime.now().strftime('%H:%M:%S')}")
    print("Ready for next build.\n")

    input("Press Enter to close this window...")

if __name__ == "__main__":
    main()

#!/usr/bin/env python3

"""

Post-Build OTA Helper for Visual Micro

"""

import sys

import os

import subprocess

from datetime import datetime

# ============== CONFIGURATION ==============

VERBOSE = False # Set to True only when debugging

# ===========================================

def main():

print("\n" + "="*60)

print("Post-Build OTA Transfer to Pi5")

print("="*60)

if VERBOSE:

print("\n=== Visual Micro Path Variables ===")

print(f"build.project_path = {sys.argv[3] if len(sys.argv) > 3 else 'Not provided'}")

print(f"vm.runtime.build.intermediate_output_path = {sys.argv[4] if len(sys.argv) > 4 else 'Not provided'}")

print(f"vm.runtime.build.final_output_path = {sys.argv[1] if len(sys.argv) > 1 else 'Not provided'}")

print("="*40)

if len(sys.argv) < 4:

print("ERROR: Not enough arguments provided.")

input("Press Enter to close...")

sys.exit(1)

intermediate_path = sys.argv[4].rstrip('\\')

project_name = sys.argv[2] if len(sys.argv) > 2 else "Unknown"

#hex_path = f"{intermediate_path}\\Wifi_OTA_Demo.hex"

hex_path = f"{intermediate_path}\\Wifi_OTA.hex"

if VERBOSE:

print("\n=== Derived File Paths ===")

print(f"Project Name : {project_name}")

print(f"Intermediate Dir : {intermediate_path}")

print(f"Hex File Path : {hex_path}")

print("="*40)

print(f"Time : {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

if not os.path.exists(hex_path):

print(f"ERROR: Hex file not found: {hex_path}")

input("Press Enter to close...")

sys.exit(1)

print("\nCopying .hex to Pi5...")

try:

#subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/firmware/latest.hex"],

# capture_output=True, text=True, check=True)

subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/latest.hex"],

capture_output=True, text=True, check=True)

print("SUCCESS: .hex file copied to Pi5.")

except subprocess.CalledProcessError:

print("\nERROR: Failed to copy .hex file to Pi5.")

if VERBOSE:

print("Check that the Pi5 is reachable and scp is set up.")

sys.exit(1)

except FileNotFoundError:

print("\nERROR: 'scp' command not found. Is OpenSSH installed?")

sys.exit(1)

print(f"\nPost-build completed at {datetime.now().strftime('%H:%M:%S')}")

print("Ready for next build.\n")

input("Press Enter to close this window...")

if __name__ == "__main__":

main()

Here’s a short video showing the Wifi_OTA update process. The video starts just after I pressed F5 to start the debug compile on my PC. After about two seconds, the built-in LED on the Teensy 4.1 (lower-left foreground) goes OFF when the HEX file transfer starts. The file transfer takes about 30 sec, and then a few seconds after the file transfer finishes, the built-in LED on the Teensy 4.1 blinks twice and then stays ON, confirming that the update was successful.

A significant part of this little sub-project was getting the Git repository set up and running, on my PC, on the pi5, and on GitHub. The same folder structure is used in all three locations, but the pi5 side only updates entries in the ‘pi5’ subfolders, and the PC side only updates the Teensy firmware. When I do an update either on the PC or the pi5, I follow the same steps each time:

git pull origin main <<— synchs the local repo with the master on Github
git add -A <<– adds anything new to the local repo
git commit -m “put my update description here”
git push origin main <<– synchs the Github repo with the updated local repo.

At this point I believe I have the basic infrastructure in place to proceed with the real project of adding vision-processing-based navigation capabilities to the robot
The OAKD-Lite camera is installed and confirmed working
The pi5 is installed and connected to the OAKD-Lite camera and via Serial1 to the Teensy4.1.
Teensy firmware can be updated via the new Wifi_OTA update channel
The Hall-effect wheel encoders are installed and confirmed working.
The next big step is to integrate the ROS (Robot Operating System) with the OAKD-Lite camera and the Teensy.

Stay Tuned!

Teensy Firmware OTA Update Via SSH to Pi5

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Posted 21 June 2026

After getting OTA via Bluetooth to the onboard HC-05 going for the 2-wheel robot, I had an epiphany; For vision processing the 2-wheel robot uses an on-board Raspberry Pi5 with a Wi-Fi connection to my local network (and thence to my PC), so why use the HC-05 link at all? The Wi-Fi connection is much more robust than the BT/HC-05 link and is available throughout the house. The pi5 has a serial port, so in theory I could simply write a small python script to pipe characters back and forth between its Wi-Fi port and its serial port, just as the HC-05 does between its BT port and its serial port. How hard could it be?

Grok Code and I have been working on this issue for a while now and have gotten to the point where we can transfer the .HEX file from the pi5 to the Teensy once, but not multiple times. This indicates that the firmware update did not happen correctly. Also, we haven’t yet figured out how to automatically transfer the HEX file resulting from a Visual Studio compile to the pi5 so that it can be passed to the Teensy via the pi5’s serial port so we are bypassing this step by using SCP (or a copy/paste using VS Code) to create a duplicate of the HEX file on the pi5; then all the pi5 script has to do is pass lines from the local HEX file to the Teensy via serial.

Grok Code and I have been trying to troubleshoot this problem, and we don’t seem to be getting anywhere. Grok does not really know how to troubleshoot in an organized manner – it is more of a ‘random walk’ process. This post is intended to document my own troubleshooting efforts.

First, what is the basic problem? The basic problem is that multiple transfers of a HEX firmware file to the Teensy using the established BT/HC-05/Serial2 succeed, but the same process using the Wi-Fi/pi5/Serial1 link appears to succeed the first time but fails on the second attempt. Since the firmware HEX files in the two cases are identical, the problem must be somewhere in the pi5 script, either in the way lines are read from the local HEX file or in the way lines are transferred to the Teensy.

A basic assumption in the above is that the HEX file transferred to the Teensy via BT/HC-05 and the HEX file transferred to the Teensy via Wi-Fi/Pi5 are identical, so I decided to start there. Are they really identical?

Compiled firmware on VS, copy/pasted (using VS Code) from “C:\Users\Frank\Documents\Arduino\Wifi_OTA_Demo\obj\x64\Debug\Wifi_OTA_Demo.hex” to “/home/pi/my_vision_robot/tests/Wifi_OTA_Demo/Wifi_OTA_Demo.hex”. Then I copy/pasted from the pi5 file to notepad++ and compared with the original – they matched perfectly.
I modified FxUtil.cpp’s update_firmware() to add the line “out->println(line);” then updated Teensy firmware using USB connector to establish ‘known-good’ baseline. Then used pi5 script to transfer its local copy of the firmware to the Teensy, logging the transfer via VS serial monitor. The file as logged going into the Teensy and the source file on the pi5 also match perfectly. This pretty much eliminates a corrupted file transfer as the source of the problem.
Then I performed the same procedure except using the BT/HC-05 channel instead of the Wifi/Pi5 channel.

Here’s the Wifi_OTA_Demo.ino file used to run the above tests:

// Generated on: 2026-06-17 14:30:00 UTC
// Wifi_OTA_Demo.ino - UART OTA Test via Pi5 Serial1

#include "FXUtil.h"
extern "C"
{
#include "FlashTxx.h"
}

#define USING_HC05
//needed for compile-time switching
char c; 
uint32_t buffer_addr, buffer_size;

void setup()
{
  Serial.begin(115200);      // USB debug

#ifdef USING_HC05
  Serial2.begin(115200);     // UART to HC05
  Serial2.println("\n=== Wifi_OTA_Demo - UART OTA Ready ===");
  Serial2.println("Send 'U' from TeraTerm on Serial2 to trigger OTA update");
#else
  Serial1.begin(115200);     // UART to Pi5
  //Serial1.println("\n=== Wifi_OTA_Demo - UART OTA Ready ===");
  //Serial1.println("Send 'U' from Pi5 on Serial1 to trigger OTA update");
#endif

  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, HIGH);

}

void loop()
{
#ifdef USING_HC05

  if (Serial2.available())
  {
    c = Serial2.read();
    Serial2.printf("Received %c on Serial2: '\n", c);

    if (c == 'U' || c == 'u')
    {
      Serial2.println("\nStart Program Update - Send new HEX file!");
      digitalWrite(LED_BUILTIN, LOW);   // visual feedback
      delay(500);

      //uint32_t buffer_addr, buffer_size;
      if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)
      {
        Serial2.println("Failed to init buffer");
        digitalWrite(LED_BUILTIN, HIGH);
        return;
      }

      Serial2.println("Calling update_firmware() on Serial2...");
      while (Serial2.available()) Serial2.read(); // clear buffer
      update_firmware(&Serial2, &Serial2, buffer_addr, buffer_size);
    }
#else
  if (Serial1.available())
  {
    c = Serial1.read();
    Serial1.printf("Received %c on Serial1: '\n", c);
    Serial1.print(c);
  }
  if (c == 'U' || c == 'u')
  {
    Serial.println("\nStart Program Update - Send new HEX file!");
    digitalWrite(LED_BUILTIN, LOW);   // visual feedback
    delay(500);

    //uint32_t buffer_addr, buffer_size;
    if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)
    {
      Serial.println("Failed to init buffer");
      digitalWrite(LED_BUILTIN, HIGH);
      return;
    }
  //}

    while (Serial1.available()) Serial1.read(); // clear buffer

    Serial.println("Calling update_firmware() on Serial1...");
    //update_firmware(&Serial1, &Serial1, buffer_addr, buffer_size);
    update_firmware(&Serial1, &Serial, buffer_addr, buffer_size);

    //firmware_buffer_free(buffer_addr, buffer_size);
    //Serial.println("Firmware update call completed. About to REBOOT...");
    //delay(1000);  // Give time for the message to be sent
#endif

      //firmware_buffer_free(buffer_addr, buffer_size);
#ifdef USING_HC05
    Serial2.println("after update_firmware");
    firmware_buffer_free(buffer_addr, buffer_size);
    Serial2.println("Firmware update call completed. About to REBOOT...");
#else
    Serial.println("after update_firmware");
    firmware_buffer_free(buffer_addr, buffer_size);
    Serial.println("Firmware update call completed. About to REBOOT...");
#endif
    delay(1000);  // Give time for the message to be sent

      REBOOT;
    }
  }

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// Generated on: 2026-06-17 14:30:00 UTC

// Wifi_OTA_Demo.ino - UART OTA Test via Pi5 Serial1

#include "FXUtil.h"

extern "C"

{

#include "FlashTxx.h"

}

#define USING_HC05

//needed for compile-time switching

char c;

uint32_t buffer_addr, buffer_size;

void setup()

{

Serial.begin(115200); // USB debug

#ifdef USING_HC05

Serial2.begin(115200); // UART to HC05

Serial2.println("\n=== Wifi_OTA_Demo - UART OTA Ready ===");

Serial2.println("Send 'U' from TeraTerm on Serial2 to trigger OTA update");

#else

Serial1.begin(115200); // UART to Pi5

//Serial1.println("\n=== Wifi_OTA_Demo - UART OTA Ready ===");

//Serial1.println("Send 'U' from Pi5 on Serial1 to trigger OTA update");

#endif

pinMode(LED_BUILTIN, OUTPUT);

digitalWrite(LED_BUILTIN, HIGH);

}

void loop()

{

#ifdef USING_HC05

if (Serial2.available())

{

c = Serial2.read();

Serial2.printf("Received %c on Serial2: '\n", c);

if (c == 'U' || c == 'u')

{

Serial2.println("\nStart Program Update - Send new HEX file!");

digitalWrite(LED_BUILTIN, LOW); // visual feedback

delay(500);

//uint32_t buffer_addr, buffer_size;

if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)

{

Serial2.println("Failed to init buffer");

digitalWrite(LED_BUILTIN, HIGH);

return;

}

Serial2.println("Calling update_firmware() on Serial2...");

while (Serial2.available()) Serial2.read(); // clear buffer

update_firmware(&Serial2, &Serial2, buffer_addr, buffer_size);

}

#else

if (Serial1.available())

{

c = Serial1.read();

Serial1.printf("Received %c on Serial1: '\n", c);

Serial1.print(c);

}

if (c == 'U' || c == 'u')

{

Serial.println("\nStart Program Update - Send new HEX file!");

digitalWrite(LED_BUILTIN, LOW); // visual feedback

delay(500);

//uint32_t buffer_addr, buffer_size;

if (firmware_buffer_init(&buffer_addr, &buffer_size) == 0)

{

Serial.println("Failed to init buffer");

digitalWrite(LED_BUILTIN, HIGH);

return;

}

//}

while (Serial1.available()) Serial1.read(); // clear buffer

Serial.println("Calling update_firmware() on Serial1...");

//update_firmware(&Serial1, &Serial1, buffer_addr, buffer_size);

update_firmware(&Serial1, &Serial, buffer_addr, buffer_size);

//firmware_buffer_free(buffer_addr, buffer_size);

//Serial.println("Firmware update call completed. About to REBOOT...");

//delay(1000); // Give time for the message to be sent

#endif

//firmware_buffer_free(buffer_addr, buffer_size);

#ifdef USING_HC05

Serial2.println("after update_firmware");

firmware_buffer_free(buffer_addr, buffer_size);

Serial2.println("Firmware update call completed. About to REBOOT...");

#else

Serial.println("after update_firmware");

firmware_buffer_free(buffer_addr, buffer_size);

Serial.println("Firmware update call completed. About to REBOOT...");

#endif

delay(1000); // Give time for the message to be sent

REBOOT;

}

25 June 2026 Update:

Grok Code and finally managed to get the Teensy OTA update via Pi5/Serial1 working. Here is the final Python script on the Pi5:

#!/usr/bin/env python3
"""
Wifi_OTA_Demo.py - Final version for ongoing vision-enhanced robot project
Last updated: 2026-06-24
"""

import serial
import time
import sys
import os
from datetime import datetime

def ota_upload(hex_file_path):
    if not os.path.exists(hex_file_path):
        print(f"Error: Hex file not found: {hex_file_path}")
        return False

    print(f"\n=== OTA Upload Started at {datetime.now().strftime('%Y-%m-%d %H:%M:%S')} ===")
    print(f"File: {hex_file_path}\n")

    ser = serial.Serial(port='/dev/ttyAMA0', baudrate=115200, timeout=3)

    try:
        print("Sending 'U' trigger...")
        ser.write(b'U')
        time.sleep(1.0)

        print("Waiting for Teensy prompt...")
        start = time.time()
        while time.time() - start < 10:
            if ser.in_waiting:
                line = ser.readline().decode('utf-8', errors='replace').strip()
                print(f"Teensy: {line}")
                if "reading hex lines" in line.lower():
                    print("✓ Got prompt")
                    break
            time.sleep(0.2)
        else:
            print("✗ Timed out waiting for prompt")
            return False

        # Send file
        print("Sending .hex file...")
        line_count = 0
        with open(hex_file_path, 'r') as f:
            for line_count, line in enumerate(f, 1):
                ser.write(line.encode('utf-8'))
                if line_count % 200 == 0:      # Fixed: was line_num
                    time.sleep(0.005)

        print(f"Sent {line_count} lines. Sending EOF...")
        ser.write(b':00000001FF\r\n')
        ser.flush()
        time.sleep(1.0)

        # Line count confirmation
        print("Waiting for line count prompt...")
        start = time.time()
        while time.time() - start < 15:
            if ser.in_waiting:
                line = ser.readline().decode('utf-8', errors='replace').strip()
                print(f"Teensy: {line}")
                if "enter" in line.lower() and "flash" in line.lower():
                    parts = line.split()
                    if len(parts) > 1 and parts[1].isdigit():
                        num = parts[1]
                        print(f"Sending line count: {num}")
                        ser.write((num + '\r\n').encode('utf-8'))
                        ser.flush()
                        break
            time.sleep(0.3)

        print("\n✅ OTA UPDATE SUCCESSFUL!")
        print("   Flash process started.")
        print("   Waiting for Teensy reboot and Serial1 re-initialization...\n")
        
        time.sleep(12)                    # Important for reliable reboot
        print("Upload process finished. You can now check Serial1 output.\n")
        return True

    except Exception as e:
        print(f"Error during OTA: {e}")
        return False
    finally:
        ser.close()

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python3 Wifi_OTA_Demo.py <full_path_to_.hex>")
        sys.exit(1)
    
    ota_upload(sys.argv[1])

#!/usr/bin/env python3

"""

Wifi_OTA_Demo.py - Final version for ongoing vision-enhanced robot project

Last updated: 2026-06-24

"""

import serial

import time

import sys

import os

from datetime import datetime

def ota_upload(hex_file_path):

if not os.path.exists(hex_file_path):

print(f"Error: Hex file not found: {hex_file_path}")

return False

print(f"\n=== OTA Upload Started at {datetime.now().strftime('%Y-%m-%d %H:%M:%S')} ===")

print(f"File: {hex_file_path}\n")

ser = serial.Serial(port='/dev/ttyAMA0', baudrate=115200, timeout=3)

try:

print("Sending 'U' trigger...")

ser.write(b'U')

time.sleep(1.0)

print("Waiting for Teensy prompt...")

start = time.time()

while time.time() - start < 10:

if ser.in_waiting:

line = ser.readline().decode('utf-8', errors='replace').strip()

print(f"Teensy: {line}")

if "reading hex lines" in line.lower():

print("✓ Got prompt")

break

time.sleep(0.2)

else:

print("✗ Timed out waiting for prompt")

return False

# Send file

print("Sending .hex file...")

line_count = 0

with open(hex_file_path, 'r') as f:

for line_count, line in enumerate(f, 1):

ser.write(line.encode('utf-8'))

if line_count % 200 == 0: # Fixed: was line_num

time.sleep(0.005)

print(f"Sent {line_count} lines. Sending EOF...")

ser.write(b':00000001FF\r\n')

ser.flush()

time.sleep(1.0)

# Line count confirmation

print("Waiting for line count prompt...")

start = time.time()

while time.time() - start < 15:

if ser.in_waiting:

line = ser.readline().decode('utf-8', errors='replace').strip()

print(f"Teensy: {line}")

if "enter" in line.lower() and "flash" in line.lower():

parts = line.split()

if len(parts) > 1 and parts[1].isdigit():

num = parts[1]

print(f"Sending line count: {num}")

ser.write((num + '\r\n').encode('utf-8'))

ser.flush()

break

time.sleep(0.3)

print("\n✅ OTA UPDATE SUCCESSFUL!")

print(" Flash process started.")

print(" Waiting for Teensy reboot and Serial1 re-initialization...\n")

time.sleep(12) # Important for reliable reboot

print("Upload process finished. You can now check Serial1 output.\n")

return True

except Exception as e:

print(f"Error during OTA: {e}")

return False

finally:

ser.close()

if __name__ == "__main__":

if len(sys.argv) < 2:

print("Usage: python3 Wifi_OTA_Demo.py <full_path_to_.hex>")

sys.exit(1)

ota_upload(sys.argv[1])

And here is the Teensy sketch used for the test:

To verify that the OTA update code performed properly, I ran the update three times in a row. The first time replaces whatever sketch was on the Teensy with my test sketch (that also includes the code that supports further updates), and the second and third updates confirm that the first (and the second) updates contained the crucial update support code.

At this point the ‘Wifi_OTA_Demo’ project is pretty much finished. The only step remaining is to fully automate the process.

27 June 2026 Update:

Now I have the update process updated to the point where I can press ‘F5’ in Visual Studio in an OTA-equipped Teensy project and have the resulting .hex file automatically copied over to the pi5. Here are the relevant files:

board.txt:

Updated 06/27/26 Post-Build: Copy .hex to Pi5

recipe.hooks.deploy.preupload.1.pattern=python "C:\Users\Frank\Documents\Robot_Projects\Wifi_OTA\PostBuild_OTA.py" "{vm.runtime.build.final_output_path}" "{build.project_name}" "{build.project_path}" "{vm.runtime.build.intermediate_output_path}"
recipe.hooks.deploy.preupload.1.use_shell_execute=true

recipe.hooks.deploy.preupload.1.pattern=python "C:\Users\Frank\Documents\Robot_Projects\Wifi_OTA\PostBuild_OTA.py" "{vm.runtime.build.final_output_path}" "{build.project_name}" "{build.project_path}" "{vm.runtime.build.intermediate_output_path}"

recipe.hooks.deploy.preupload.1.use_shell_execute=true

PostBuild_OTA.py:

#!/usr/bin/env python3
"""
Post-Build OTA Helper for Visual Micro
"""

import sys
import os
import subprocess
from datetime import datetime

# ============== CONFIGURATION ==============
VERBOSE = False         # Set to True only when debugging
# ===========================================

def main():
    print("\n" + "="*60)
    print("Post-Build OTA Transfer to Pi5")
    print("="*60)

    if VERBOSE:
        print("\n=== Visual Micro Path Variables ===")
        print(f"build.project_path              = {sys.argv[3] if len(sys.argv) > 3 else 'Not provided'}")
        print(f"vm.runtime.build.intermediate_output_path = {sys.argv[4] if len(sys.argv) > 4 else 'Not provided'}")
        print(f"vm.runtime.build.final_output_path = {sys.argv[1] if len(sys.argv) > 1 else 'Not provided'}")
        print("="*40)

    if len(sys.argv) < 4:
        print("ERROR: Not enough arguments provided.")
        input("Press Enter to close...")
        sys.exit(1)

    intermediate_path = sys.argv[4].rstrip('\\')
    project_name = sys.argv[2] if len(sys.argv) > 2 else "Unknown"
    #hex_path = f"{intermediate_path}\\Wifi_OTA_Demo.hex"
    hex_path = f"{intermediate_path}\\Wifi_OTA.hex"

    if VERBOSE:
        print("\n=== Derived File Paths ===")
        print(f"Project Name     : {project_name}")
        print(f"Intermediate Dir : {intermediate_path}")
        print(f"Hex File Path    : {hex_path}")
        print("="*40)
        print(f"Time : {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

    if not os.path.exists(hex_path):
        print(f"ERROR: Hex file not found: {hex_path}")
        input("Press Enter to close...")
        sys.exit(1)

    print("\nCopying .hex to Pi5...")
    
    try:
        subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/firmware/latest.hex"], 
                       capture_output=True, text=True, check=True)
        print("SUCCESS: .hex file copied to Pi5.")
    except subprocess.CalledProcessError:
        print("\nERROR: Failed to copy .hex file to Pi5.")
        if VERBOSE:
            print("Check that the Pi5 is reachable and scp is set up.")
        sys.exit(1)
    except FileNotFoundError:
        print("\nERROR: 'scp' command not found. Is OpenSSH installed?")
        sys.exit(1)

    print(f"\nPost-build completed at {datetime.now().strftime('%H:%M:%S')}")
    print("Ready for next build.\n")

    input("Press Enter to close this window...")

if __name__ == "__main__":
    main()

#!/usr/bin/env python3

"""

Post-Build OTA Helper for Visual Micro

"""

import sys

import os

import subprocess

from datetime import datetime

# ============== CONFIGURATION ==============

VERBOSE = False # Set to True only when debugging

# ===========================================

def main():

print("\n" + "="*60)

print("Post-Build OTA Transfer to Pi5")

print("="*60)

if VERBOSE:

print("\n=== Visual Micro Path Variables ===")

print(f"build.project_path = {sys.argv[3] if len(sys.argv) > 3 else 'Not provided'}")

print(f"vm.runtime.build.intermediate_output_path = {sys.argv[4] if len(sys.argv) > 4 else 'Not provided'}")

print(f"vm.runtime.build.final_output_path = {sys.argv[1] if len(sys.argv) > 1 else 'Not provided'}")

print("="*40)

if len(sys.argv) < 4:

print("ERROR: Not enough arguments provided.")

input("Press Enter to close...")

sys.exit(1)

intermediate_path = sys.argv[4].rstrip('\\')

project_name = sys.argv[2] if len(sys.argv) > 2 else "Unknown"

#hex_path = f"{intermediate_path}\\Wifi_OTA_Demo.hex"

hex_path = f"{intermediate_path}\\Wifi_OTA.hex"

if VERBOSE:

print("\n=== Derived File Paths ===")

print(f"Project Name : {project_name}")

print(f"Intermediate Dir : {intermediate_path}")

print(f"Hex File Path : {hex_path}")

print("="*40)

print(f"Time : {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

if not os.path.exists(hex_path):

print(f"ERROR: Hex file not found: {hex_path}")

input("Press Enter to close...")

sys.exit(1)

print("\nCopying .hex to Pi5...")

try:

subprocess.run(["scp", hex_path, "pi@RobotPi5:~/my_vision_robot/firmware/latest.hex"],

capture_output=True, text=True, check=True)

print("SUCCESS: .hex file copied to Pi5.")

except subprocess.CalledProcessError:

print("\nERROR: Failed to copy .hex file to Pi5.")

if VERBOSE:

print("Check that the Pi5 is reachable and scp is set up.")

sys.exit(1)

except FileNotFoundError:

print("\nERROR: 'scp' command not found. Is OpenSSH installed?")

sys.exit(1)

print(f"\nPost-build completed at {datetime.now().strftime('%H:%M:%S')}")

print("Ready for next build.\n")

input("Press Enter to close this window...")

if __name__ == "__main__":

main()

The next step is to put these two steps (copy the .hex file to the pi5, and then launch the update code that xfers the .hex file to the Teensy) together into one seamless automated process.