Configure the RS485 port Modbus/RTU settings
ModbusPortConfig( speed, settings )
This command will configure the RS485 port.
 speed  | Desired bit rate (1200 - 115200 bps) | 
 settings  | Bitmap combination of UART_WLEN_*, UART_STOP_* and UART_PAR_* | 
 UART_WLEN_8  | 8 data bits | 
 UART_WLEN_7  | 7 data bits | 
 UART_STOP_ONE  | Transmit one stop bit (receiving will always accept one or two stopbits) | 
 UART_STOP_TWO  | Transmit two stop bits (receiving will always accept one or two stopbits) | 
 UART_PAR_NONE  | No parity bit | 
 UART_PAR_EVEN  | Even parity | 
 UART_PAR_ODD  | Odd parity | 
No return value.
ModbusPortConfig( 19200, UART_WLEN_8 | UART_STOP_ONE | UART_PAR_NONE );