Writing to a second serial connection in a thread has errors #874
Description
Running on a Pi Pico with MicroPython 1.23.0 and whatever the latest version of usb-device-cdc is in mip; code to reproduce:
from utime import sleep_ms, time
from _thread import start_new_thread
import usb.device
from usb.device.cdc import CDCInterface
SERIAL_TWO = None
def update():
while True:
print("Update: {}".format(time()), file=SERIAL_TWO, end="\r\n")
sleep_ms(1000)
def main():
global SERIAL_TWO
SERIAL_TWO = CDCInterface()
SERIAL_TWO.init(timeout=0)
usb.device.get().init(SERIAL_TWO, builtin_driver=True)
while not SERIAL_TWO.is_open():
sleep_ms(100)
start_new_thread(update, ())
while True:
sleep_ms(1000)
if __name__ == "__main__": main()If you connect to both ports with mpremote a0 and mpremote a1, you'll see this error sporadically:
Traceback (most recent call last):
File "usb/device/core.py", line 316, in _xfer_cb
File "usb/device/cdc.py", line 327, in _wr_cb
File "usb/device/core.py", line 833, in finish_read
AssertionError:
But I did see this error once:
Unhandled exception in thread started by <function update at 0x2000aef0>
Traceback (most recent call last):
File "<stdin>", line 12, in update
File "usb/device/cdc.py", line 356, in write
File "usb/device/cdc.py", line 322, in _wr_xfer
File "usb/device/core.py", line 570, in submit_xfer
File "usb/device/core.py", line 302, in _submit_xfer
RuntimeError: xfer_pending