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Cannot init USB devices in boot.py

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
embedded-iot

Research direction

Reproduce the example using boot.py and main.py on MicroPython 1.23 with the latest usb-device-cdc release. Start by tracing usb.device.get().init() and CDCInterface.init(timeout=0) to compare initialization in boot.py with later execution. Done when the supported boot.py behavior is established and the process error is fixed or clearly documented.

Written by the indexing model from the issue text.

Description

bug

I tested this on a pico running MP 1.23 and the latest release of usb-device-cdc.

boot.py:

import usb.device
from usb.device.cdc import CDCInterface

IFACE_TWO = CDCInterface()
IFACE_TWO.init(timeout=0)
#usb.device.get().init(IFACE_TWO, builtin_driver=True)

main.py:

from time import sleep_ms

def main():
	while True:
		print(IFACE_TWO)
		sleep_ms(1000)

if __name__ == "__main__": main()

Running this as-is, IFACE_TWO does show up in main.py, but uncommenting the init function causes the process to error out. This discord post suggests you can call usb.device.get.init() in boot.py, is this no longer true?

Dominant language
Python
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Merged PRs (30d)
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