Telemetrix: Fix Disconnect/Reconnect Issues

Nov 13, 2025 by Admin 44 views

Telemetrix Disconnect and Reconnect Issue

Hey everyone! Today, let's dive into a peculiar problem some of us have encountered while using the Telemetrix library with Arduino: the dreaded disconnect and reconnect issue. Specifically, we're talking about how automatic port detection can fail after the initial connection. It's a bit of a head-scratcher, but fear not, we'll explore the issue, understand why it happens, and provide some solid solutions.

The Problem: Automatic Port Detection Fails

So, here's the scenario: You connect to your Arduino using Telemetrix with automatic port detection, everything works like a charm. You disconnect, maybe to upload new code or just to reset things. But when you try to reconnect using that same automatic port detection, bam! It crashes. Sounds familiar? You're not alone.

The code snippet that usually triggers this looks something like this:

board = Telemetrix()  # Works fine, connects to a COM port (e.g., COM12)
board.shutdown()
board = Telemetrix()  # Fails on the second attempt
board.shutdown()
board = Telemetrix(com_port="COM12")  # Works again if the previous error is caught
board.shutdown()

Diving Deep into the Error

When this happens, you might see a traceback that looks a little something like this:

Telemetrix: Version 1.43
Copyright (c) 2021 Alan Yorinks All Rights Reserved.
Opening all potential serial ports...
COM12
Waiting 4 seconds(arduino_wait) for Arduino devices to reset...
Valid Arduino ID Found.
Arduino compatible device found and connected to COM12
Waiting for Arduino to reset
Reset Complete
Retrieving Telemetrix4Arduino firmware ID...
Telemetrix4Arduino firmware version: 5.4.4
Telemetrix: Version 1.43
Copyright (c) 2021 Alan Yorinks All Rights Reserved.
Opening all potential serial ports...
Waiting 4 seconds(arduino_wait) for Arduino devices to reset...
Traceback (most recent call last):
  File "C:\Users\nicol\AppData\Local\Programs\Python\Python313\Lib\site-packages\telemetrix\telemetrix.py", line 1780, in shutdown
    self._send_command(command)
  File "C:\Users\nicol\AppData\Local\Programs\Python\Python313\Lib\site-packages\telemetrix\telemetrix.py", line 2361, in _send_command
    raise RuntimeError('No serial port or ip address set.')
RuntimeError: No serial port or ip address set.
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "c:\Users\nicol\Desktop\test\a.py", line 5, in <module>
    board = Telemetrix()  # Fails
  File "C:\Users\nicol\AppData\Local\Programs\Python\Python313\Lib\site-packages\telemetrix\telemetrix.py", line 292, in __init__
    self._find_arduino()
  File "C:\Users\nicol\AppData\Local\Programs\Python\Python313\Lib\site-packages\telemetrix\telemetrix.py", line 412, in _find_arduino
    self.shutdown()
  File "C:\Users\nicol\AppData\Local\Programs\Python\Python313\Lib\site-packages\telemetrix\telemetrix.py", line 1800, in shutdown
    raise RuntimeError('Shutdown failed - could not send stop streaming message')
RuntimeError: Shutdown failed - could not send stop streaming message

Why Does This Happen?

Understanding the Root Cause is key to fixing this issue. When Telemetrix tries to automatically find the Arduino, it scans available serial ports. After the first connection, there might be some lingering state or a race condition that prevents it from properly re-identifying the port on the subsequent attempt. The shutdown() method might not be fully releasing the resources, or the Arduino might not be fully reset before Telemetrix tries to reconnect.

Solutions to the Rescue

Alright, let's get our hands dirty and fix this thing! Here are a few approaches you can take to resolve the disconnect/reconnect issue with Telemetrix.

1. Explicitly Specify the COM Port

The most reliable solution is to avoid automatic port detection altogether after the first connection. Instead, explicitly specify the COM port. Remember how our code snippet showed that specifying the COM port directly works? That's because it bypasses the automatic detection process, which is where the problem lies.

Here's how you can implement this:

try:
    board = Telemetrix()
    com_port = board.port  # Store the automatically detected port
    board.shutdown()
except Exception as e:
    print(f"An error occurred: {e}")

# Now, reconnect using the stored COM port
try:
    board = Telemetrix(com_port=com_port)
    # Your code here
    board.shutdown()
except Exception as e:
    print(f"An error occurred: {e}")

In this approach, we first let Telemetrix automatically detect the port, then we grab the detected port name and store it. After the initial shutdown, we use that stored port name to reconnect. This ensures that Telemetrix knows exactly where to find the Arduino, avoiding the pitfalls of automatic detection on subsequent connections.

2. Implement Error Handling with Try-Except Blocks

Wrapping your code in try-except blocks is crucial for gracefully handling errors. Even if automatic port detection fails, you can catch the exception and attempt to reconnect using a manual port.

try:
    board = Telemetrix()
    board.shutdown()
except Exception as e:
    print(f"An error occurred: {e}")
    # Attempt to reconnect using a specific COM port
    try:
        board = Telemetrix(com_port="COM12")  # Replace COM12 with your port
        # Your code here
        board.shutdown()
    except Exception as e:
        print(f"An error occurred during manual reconnect: {e}")

This method ensures that even if the initial automatic connection fails, the program doesn't crash. Instead, it attempts a manual reconnection, providing a more robust solution.

3. Add a Delay Before Reconnecting

Sometimes, the Arduino might need a little more time to fully reset after a disconnection. Adding a short delay before attempting to reconnect can help.

import time

try:
    board = Telemetrix()
    board.shutdown()
except Exception as e:
    print(f"An error occurred: {e}")

# Add a delay before reconnecting
time.sleep(2)  # Wait for 2 seconds

try:
    board = Telemetrix()
    # Your code here
    board.shutdown()
except Exception as e:
    print(f"An error occurred during reconnect: {e}")

A time.sleep() call introduces a brief pause, giving the Arduino enough time to reset properly before Telemetrix attempts to establish a new connection. Experiment with different delay durations to find what works best for your setup.

4. Check Arduino Resetting

Ensure your Arduino board resets properly after the shutdown() call. Some boards might require a manual reset or a specific command to ensure they are ready for a new connection.

try:
    board = Telemetrix()
    board.shutdown()
    # Add code to manually reset the Arduino if needed
except Exception as e:
    print(f"An error occurred: {e}")

# Attempt to reconnect
try:
    board = Telemetrix()
    # Your code here
    board.shutdown()
except Exception as e:
    print(f"An error occurred during reconnect: {e}")

Depending on your Arduino board, you might need to send a specific signal or use a hardware reset button to ensure it's fully reset before reconnecting.

5. Update Telemetrix and Telemetrix4Arduino

Make sure you're running the latest versions of both the Telemetrix Python library and the Telemetrix4Arduino firmware on your Arduino. Outdated versions can sometimes have bugs that are resolved in newer releases.

To update the Telemetrix library, use pip:

pip install --upgrade telemetrix

To update the Telemetrix4Arduino firmware, follow the instructions in the Telemetrix documentation.

Putting It All Together

Here's an example that combines error handling, explicit COM port specification, and a delay:

import time

try:
    board = Telemetrix()
    com_port = board.port
    board.shutdown()
except Exception as e:
    print(f"An error occurred: {e}")
    com_port = None  # Set com_port to None if initial connection fails

if com_port:
    time.sleep(2)
    try:
        board = Telemetrix(com_port=com_port)
        # Your code here
        board.shutdown()
    except Exception as e:
        print(f"An error occurred during reconnect: {e}")
else:
    print("Failed to obtain COM port during initial connection.")

This comprehensive approach first tries to connect automatically and retrieve the COM port. If that fails, it sets com_port to None. If the initial connection is successful, it waits for a couple of seconds and then attempts to reconnect using the stored COM port. If the initial connection fails, it indicates that it couldn't obtain the COM port.

Conclusion

The Telemetrix disconnect/reconnect issue can be a bit annoying, but with the right strategies, it's definitely manageable. By explicitly specifying the COM port, implementing robust error handling, adding delays, and ensuring your Arduino resets properly, you can create a more stable and reliable connection. Happy coding, folks! Remember, persistence is key and keep experimenting to find the best solution for your specific setup.