Need free serial port on Jetson TX2

I’m trying to find a free serial port that’s not used on the TX2.
It looks like /dev/ttyS0 which is on J21 pins 8 and 10 are used for boot messages and a console.
I’ve tried using the J17 serial port, but I can’t see to find which /dev/tty corresponds to it.
Any help appreciated.


Figured it out with a Salea logic analyzer.
/dev/ttyTHS2 is on J17. default is 9600 baud, 8n1.