Initialize Moxa UART control library.
- 0 on success.
- negative numbers on error.
Set state for target Digital Output port.
- port: target DOUT port number
- mode: UART_MODE_RS232 or UART_MODE_RS485_2W or UART_MODE_RS422 or UART_MODE_RS485_4W
- 0 on success.
- negative numbers on error.
Get state from target Digital Output port.
- port: target DOUT port number
- mode: where the output value will be set.
- 0 on success.
- negative numbers on error.