test Xbox on TechnicHub to show exceptions

[BertLindeman]

Demo Program: Test Pybricks Code and Save Exception Data to Storage

Purpose

This program tests a Pybricks program (blocks and Python) and saves exception details to user storage if errors occur.

Why Use This?

The TechnicHub disconnects from the PC when an Xbox controller is used.
This prevents real-time viewing of errors.
This program helps capture those errors for later analysis.

How to Use

1. Update the import line in this program to import the program you want to test. (see >>>>>> and <<<<<)
2. Run this program on your hub.
   • It will execute your program and, if any exceptions occur, write the details to user storage.
3. After the program finishes:
   • Reconnect the hub to your PC.
   • Start the REPL interface.
   • Use the provided command line (displayed during execution) to print the stored data.

The demo program source

# pylint: disable=W0105
"""
test_xbox_exception_data.py

Demo program to test a user program
and save exception data to user storage.

Rationale:
  The TechnicHub disconnects from the PC on use of an Xbox controller,
  so the user cannot see any error messages.

This program imports the program to be tested
and writes the exception info in user storage (if any).

After re-connecting the hub, start the REPL and print the data from storage
with the command line shown on execution.

"""

from pybricks.hubs import ThisHub
from pybricks import version
import usys
import uio

# Initialize hub
hub = ThisHub()

# Determine storage size based on hub type
USER_DATA_SIZE = 512 if version[0] in ["primehub", "essentialhub"] else 128

# Clean user storage and write default message if no exception occurred
hub.system.storage(0, write=b'\x00' * USER_DATA_SIZE)
hub.system.storage(0, write=b'no exception happened\n')

# Print user instructions
print("""
    After the Xbox program finished (hub light: blue "blink blink pause"):
    - Reconnect the hub and start the REPL (Blue button ">>>" on the top of the Pybricks user interface)
    - Copy the following command, and
    - Paste it onto the output window (the bottom one) and [Enter] twice:
""")
# removed all unneeded spaces in the REPL command to make it shorter.
print(
    f'for loc in range(0,{USER_DATA_SIZE}):print(str(hub.system.storage(loc,read=1),"utf-8"),end="")'
    "\n\n    Copy the command now to use it later."
)


def clean_traceback(traceback, unwanted_lines):
    """ Removes specified lines from the traceback string to keep most important data. """
    unwanted_lines = set(line.strip() for line in unwanted_lines)
    return "\n".join(line for line in traceback.split('\n') if line.strip() not in unwanted_lines)


# Execute your program and write exception data to user storage
try:
    print("\nStart of your Xbox program:")
    # Your program runs here:
    # >>>>>>>>>>>>>>>>>>>>>>>  import below >>>>>>>>
    import LR13000_top_hub_04
    # <<<<<<<<<<<<<<<<<<<<<<<  import above <<<<<<<<

except Exception as e:
    # Capture exception details
    my_file = uio.StringIO()
    usys.print_exception(e, my_file)
    traceback_info = my_file.getvalue()
    print(f'Raw traceback length: {len(traceback_info)}\n{traceback_info}=====================')

    # Clean and trim traceback to keep most important data
    TRACEBACK_PREFIX = 'Traceback (most recent call last):\n'
    if traceback_info.startswith(TRACEBACK_PREFIX):
        traceback_info = traceback_info[len(TRACEBACK_PREFIX):].strip()

    endlines = [
        "A sensor or motor is not connected to the specified port:\n",
        "--> Check the cables to each motor and sensor.\n",
        "--> Check the port settings in your script.\n",
        "--> Check the line in your script that matches\n",
        "the line number given in the 'Traceback' above.\n"
    ]

    cleaned_traceback = clean_traceback(traceback_info, endlines)
    print(cleaned_traceback)
    trail_nl = '\n' if len(cleaned_traceback) < USER_DATA_SIZE else ""
    # Write the END of the traceback to user storage (critical lines preserved)
    formatted_traceback = cleaned_traceback[-USER_DATA_SIZE:] + trail_nl
    hub.system.storage(0, write=bytes(formatted_traceback, 'utf-8'))

# print for debugging on e.g. a primehub
print("\nStored exception data:\n" + "=" * 40)
for loc in range(0, USER_DATA_SIZE):
    print(str(hub.system.storage(loc, read=1), 'utf-8'), end="")
print("\n" + "=" * 40)

Tested with

import LR13000_top_hub_04

from LEGO Liebherr LR 13000 / Xbox Controller / Pybricks

Interested if this helps somebody. 😄

Bert

[laurensvalk]

Thanks @BertLindeman !