displayio REPL output on LCD can stop updating after a control-c on long output

[kevinjwalters]

If I inspect a huge array in CircuitPython 5.0.0's REPL with the serial console output active on the LCD (on Adafruit CLUE) and interrupt the output with control-C "half" way through then the serial console over USB continues to work fine as expected but the LCD screen freezes and no longer updates.

Press any key to enter the REPL. Use CTRL-D to reload.
Adafruit CircuitPython 5.0.0 on 2020-03-02; Adafruit CLUE nRF52840 Express with nRF52840
>>>
>>>
>>>
>>>
>>> bigarray = [12345] * 10000
>>> bigarray   # press control-c after a second or two
[12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345,
 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345,
 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 
 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345,
 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345,
 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345, 12345,

[kevinjwalters]

I just experienced a variant of this or perhaps a different issue on CircuitPython 5.2.0. I tried to copy over code.py as I normally would and it paused and didn't appear to copy any bytes. After maybe 20 second Windows popped up a very unique looking error. I've never seen an Adafruit board elicit one of these before, Error 0x80070079: The semaphore timeout period has expired:

The serial console was being written to by the application and that continued for a while but then did stop and go into the "no output, only accepting control-c" mode.

After that I could copy files onto CIRCUITPY ok and it would trigger a restart of the application. The application froze and I'm guessing that's because it's blocked writing to the serial console. Reconnecting to the serial console over USB connects up but no output and oddly control-c doesn't even work.

The reset button the boad saved the day.

Actually re-reading this ticket, this is more like #2686.

[kevinjwalters]

I can't remember if control-c would actually interrupt the serial output on 5.0.0. I just tried this with lists and ulab arrays on 5.3.1 and control-c cannot interrupt a variable inspection from REPL over USB serial console.

I suppose the memory constraints of these devices mean that the output will tend to complete in a reasonable amout of time for straightforward data structures.