Using busio.UART on nRF breaks USB MSD #8366
Description
CircuitPython version
Adafruit CircuitPython 8.2.4 on 2023-08-22; Adafruit ItsyBitsy nRF52840 Express with nRF52840Code/REPL
This code demonstrates the issue:
import busio
import board
import time
uart_hw = busio.UART(board.TX, board.RX)
while True:
print("Spin Loop")
time.sleep(0.5)For comparison, this code works OK. The only difference is the use of the board.UART() singleton:
import board
import time
uart_hw = board.UART()
while True:
print("Spin Loop")
time.sleep(0.5)Behavior
The looping and printing works as expected for both code examples. The issue lies more with the subsequent effect on USB behavior. More info in Description below.
Description
With the first code example above loaded as code.py, it runs as expected with a soft reset:
>>>
soft reboot
Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Spin Loop
Spin Loop
Spin Loop
Spin Loop
Spin Loop
Spin Loop
Traceback (most recent call last):
File "code.py", line 9, in <module>
KeyboardInterrupt:
Code done running.However, after breaking out via <CTRL><C>, the REPL does not come back. At this point, the board is now in a weird/bad state. Attempting to alter files in CIRCUITPY fails. So can not recover by simply changing or deleting the offending code.py. Must get into safemode and perform a storage.erase_filesystem(), or something equivalent.
For the code that uses the board.UART() singleton, the behavior is as expected:
>>>
soft reboot
Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Spin Loop
Spin Loop
Spin Loop
Traceback (most recent call last):
File "code.py", line 8, in <module>
KeyboardInterrupt:
Code done running.
Press any key to enter the REPL. Use CTRL-D to reload.
Adafruit CircuitPython 8.2.4 on 2023-08-22; Adafruit ItsyBitsy nRF52840 Express with nRF52840
>>> print("hello")
hello
>>>The code loops and prints. Hitting <CTRL><C> breaks out and drops into REPL. The CIRCUITPY drive still behaves OK, etc. No issues.
Additional information
Related forum thread:
https://forums.adafruit.com/viewtopic.php?p=983473