Please do the following to enable and test RS-485 port:
1. Perform a loopback at RS-485 port by shorting pins 1 to 3 and 2 to 4 on J11 (on the carrier board).
2. Type the following commands in the Linux shell to enable:
$ echo 168 > /sys/class/gpio/export $ echo "out" > /sys/class/gpio/gpio168/direction $ echo 0 > /sys/class/gpio/gpio168/value # Tx enable: gpio173 $ echo 173 > /sys/class/gpio/export $ echo "out" > /sys/class/gpio/gpio173/direction $ echo 1 > /sys/class/gpio/gpio173/value
3. Start minicom
$ minicom -D/dev/ttyO2 -b115200 -8
4. Type a few characters at the minicom and see that the loopback is working.