USB-UART, which port is which?

Hi, I am working with getting some UART code running on the Alchitry AU and realized I had a question. Which of the two /dev/ttyUSB? ports is which. In the schematic JTAG seems to be port A and UART on port B, but would that necessarily give the expected result of /dev/ttyUSB0 is the JTAG and /dev/ttyUSB1?

PySerial just labels them both “Alchitry - Au”

[code]>>> from import list_ports

for element in list_ports.comports(): print(element)

/dev/ttyUSB1 - Alchitry Au - Alchitry Au
/dev/ttyUSB0 - Alchitry Au - Alchitry Au


I suspect it’s arbitrary which is which, just whichever the kernel saw first, but I was wondering if anyone had an easy way to read them and be sure.

It is likely ttyUSB1. As you’ve already noted, it is port B which is the UART which I believe should enumerate second.

That makes some sense. I don’t know enough about USB to understand how the handshake works. I figured it was whichever the kernel sees first, but if the chip enumerates things to the kernel in the same order as its output ports, what you say makes sense.