Added argument to HardwareSerial.begin to specify whether the logic levels of the UART rx and tx lines should be inverted (espressif#719)

Author: ewasscher

Diff for: cores/esp32/HardwareSerial.cpp

@@ -9,7 +9,7 @@ HardwareSerial Serial(0);
 
 HardwareSerial::HardwareSerial(int uart_nr) : _uart_nr(uart_nr), _uart(NULL) {}
 
-void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin)
+void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, bool invert)
 {
     if(0 > _uart_nr || _uart_nr > 2) {
         log_e("Serial number is invalid, please use 0, 1 or 2");
@@ -30,7 +30,7 @@ void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, in
         rxPin = 16;
         txPin = 17;
     }
-    _uart = uartBegin(_uart_nr, baud, config, rxPin, txPin, 256, false);
+    _uart = uartBegin(_uart_nr, baud, config, rxPin, txPin, 256, invert);
 }
 
 void HardwareSerial::end()

Diff for: cores/esp32/HardwareSerial.h

@@ -37,7 +37,7 @@ class HardwareSerial: public Stream
 public:
     HardwareSerial(int uart_nr);
 
-    void begin(unsigned long baud, uint32_t config=SERIAL_8N1, int8_t rxPin=-1, int8_t txPin=-1);
+    void begin(unsigned long baud, uint32_t config=SERIAL_8N1, int8_t rxPin=-1, int8_t txPin=-1, bool invert=false);
     void end();
     int available(void);
     int peek(void);