TTL
Full Duplex
device name: /dev/ttyTHS1
RS232
Full Duplex
device name: /dev/ttyTHS3
RS485
Half Duplex
device name: /dev/ttyTHS4
before send: echo 1 > /sys/class/leds/rs485_re_de/brightness
before receive: echo 0 > /sys/class/leds/rs485_re_de/brightness