VAR-SOM-AM33 RS232
From Variscite Wiki
VAR-SOM-AM33 - RS-232 Port
1. Perform a loopback at RS-232 port by shorting pins 2 & 3 in DB9 connector J24 on the carrier board, or connect to another computer.
2. Enable UART1 when on-SOM Bluetooth is not mounted. Type the following commands in the Linux shell to enable:
$ echo 20 > /sys/class/gpio/export $ echo out > /sys/class/gpio/gpio20/direction $ echo 0 > /sys/class/gpio/gpio20/value
3. Start minicom.
$ minicom -D/dev/ttyO1 -b115200 -8
4. Type a few characters at the minicom and see that the loopback is working.