getting USB serial config

[neilger]

I'd like to port this SAMD code:

https://github.com/qbolsee/SAMD11C_serial/blob/main/SAMD11C_serial/SAMD11C_serial.ino

to the RP2040; it follows changes in the USB serial config (used for AVR UPDI progamming).

These calls are not supported:

SerialUSB.baud(), SerialUSB.paritytype(), SerialUSB.stopbits(), SerialUSB.numbits()

Is it possible to get the USB serial config?

[earlephilhower]

That's a proprietary library for one chip and not compatible with the RP2040.

That said, what exactly do those calls do?

There is no such thing as a 5-bit or even parity on a USB CDC ACM serial port. Everything is sent over in byte-formatted packets. Baud rate is also ignored, this is USB and not a UART. There are a few emulated lines (DCD/etc.) but they're just informative and not real wires or real flow control (unless you manually handle it).

[qbolsee]

CDC doesn't rely on those emulated settings, but catching changes made by the host OS is still a useful feature. We have used this to make "smart" USB-UART adapters with dynamic baudrate, parity and stop bits on the UART side. Some of the Arduino cores for chips with native USB implement this, for example the Arduino Zero:
https://github.com/arduino/ArduinoCore-samd/blob/master/cores/arduino/USB/CDC.cpp

[earlephilhower]

Ah, I see. Thx for the explanation...

We don't support setting those (but we do catch host changes to them to implement the Arduino 1200bps tickle). But TinyUSB might be able to set that as a device using the struct here and the appropriate calls: https://github.com/hathach/tinyusb/blob/e95973d3462cdacd165a4057632d46248ded7b8a/src/class/cdc/cdc.h#L395-L401 You seem to have some experience, so maybe give a go at a PR for this? Everything is pretty self contained in SerialUSB.