Update portserial_m.c
add macro to aviod compile error with:
rt_pin_mode(MODBUS_MASTER_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
@@ -57,7 +57,9 @@ BOOL xMBMasterPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
* set 485 mode receive and transmit control IO
* @note MODBUS_MASTER_RT_CONTROL_PIN_INDEX need be defined by user
*/
+#if defined(RT_MODBUS_MASTER_USE_CONTROL_PIN)
rt_pin_mode(MODBUS_MASTER_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
+#endif
/* set serial name */
if (ucPORT == 1) {
