Handshaking on USB CDC not working correctly

[patrislav1]

The handshaking on the USB CDC port doesn't work correctly, so when lots of characters are copied / pasted to the terminal at once, then some get lost in the process and don't get echoed.

Reproducible with picocom /dev/ttyACM0 and the micropython-fomu.dfu from the workshop.

[tcal-x]

Thanks for filing this! I had noticed this too. I hit this mostly when I have a small Python program on the host and want to paste it into the terminal window.

I just tried playing around with a few different things. I found that specifying a slow baud rate for picocom didn't help.

I also found that flterm works much better. I was able to paste in entire 5-line programs with no dropped characters. I happened to have flterm in my path from doing a timvideos/litex-buildenv build. I had to add a line-endings option:

flterm --line-endings nl2crnl --port /dev/ttyACM0

So that's a potential workaround.

[xobs]

One issue that we should look into is directing people to use Circuit Python instead of Micropython. This is more full-featured and has actual CDC support: https://circuitpython.org/board/fomu/