uart 4.0

[ladyada]

Here are some breaking-change requests to make uart match CPython (pyserial)

• Change timeout arg to seconds rather than milliseconds
• Require bytes only, don't allow strings (e.g. uart.write("hello") should fail, but uart.write(b'hello') is ok)
• dont let readinto() take a size/numbytes
• UART.in_waiting from PySerial. Added by UART enhancements #1186.
• UART.reset_input_buffer from PySerial. Added by UART enhancements #1186.

also, any other functions/apis that vary from https://pyserial.readthedocs.io/en/latest/pyserial_api.html would be good to bring in line at the same time.

[tannewt]

Sounds good to me!

[ladyada]

another useful thing, in_waiting lets you check if there's something to read, nonblocking
https://pythonhosted.org/pyserial/pyserial_api.html#serial.Serial.in_waiting

[ladyada]

i think this ^ is also essentially what #254 is asking for

[ladyada]

reset_input_buffer() would also be great, flush input buffer, great for getting clean packets :)

[dhalbert]

Added a to-do list to initial comment. UART.in_waiting and UART.reset_input_buffer() implemented by #1186.

[PaulKierstead]

The addition of in_waiting has made non-blocking timed reads much easier; however, I think it would be very valuable to have the write_timeout separate from timeout, as is the case in pySerial. It is very common to want to wait on writes but not on reads, so separate timeouts are handy. Also useful is out_waiting, in this case so you can implement your own buffering.

I've been trying to do a bunch of asynio type stuff with the UART and those two (along with my 0 timeout fix) would be a very big boon. Of course, having the same units for timeouts would be nice too!

At some point cts/rts support might be nice, though they could be added non-breaking later.

[ladyada]

i think we're slowly going to try and add all pyserial supported functions, but ya some are more useful than others :)

[ATMakersBill]

Will there be a way to get a UART interface "on top of" the console? That is, will we be able to use these IO methods to talk to the USB Serial port (ala input() / print())?

If so, I'd like to offer to help test/debug this effort (point me at the right person please). If not, I think I'll add the "usb_bytes_available" module that Scott requested instead of the input() timeout.

Bill

[tannewt]

@ATMakersBill That's the idea in #231. We'll have UART like interface for the second USB CDC connection.

[ATMakersBill]

Hmmmm... second CDC? Will that show up as a second COM port (or tty on Linux)? If so, will there be a way to differentiate the two?