#!/bin/sh

if [[ $# -lt 1 || $# -gt 2 ]]
then
	echo 1>&2
	echo "Usage: $0 device [mode]" 1>&2
	echo 1>&2
	echo "      Mode         Description" 1>&2
	echo "      ----         -----------" 1>&2
	echo "        0          RS232" 1>&2
	echo "        1          RS422: No Terminating Resistor" 1>&2
	echo "        9          RS422: Terminating Resistor" 1>&2
	echo "       13          RS485: Half Duplex, End Unit, Echo" 1>&2
	echo "       15          RS485: Half Duplex, End Unit, No Echo" 1>&2
	echo "        5          RS485: Half Duplex, Middle Unit, Echo" 1>&2
	echo "        7          RS485: Half Duplex, Middle Unit, No Echo" 1>&2
	echo "        9          RS485: Full Duplex, End Unit, Master" 1>&2
	echo "       13          RS485: Full Duplex, End Unit, Slave" 1>&2
	echo "        1          RS485: Full Duplex, Middle Unit, Master" 1>&2
	echo "        5          RS485: Full Duplex, Middle Unit, Slave" 1>&2
	echo 1>&2
	exit 1
fi

uart_mode_path=/sys/bus/usb-serial/devices/${1##*/}/uart_mode

if [[ ! -f $uart_mode_path ]]
then
	echo "$0: cannot find $uart_mode_path"
	exit 1
fi

if [[ $# -eq 1 ]]
then
	cat $uart_mode_path
else
	echo $2 > $uart_mode_path
fi