Added facility to invert the polarity of input UART bits. (espressif#4200)

Author: brian-r-calder

cores/esp32/HardwareSerial.cpp

@@ -184,3 +184,8 @@ HardwareSerial::operator bool() const
 {
  return true;
 }
+
+void HardwareSerial::setRxInvert(bool invert)
+{
+ uartSetRxInvert(_uart, invert);
+}

cores/esp32/HardwareSerial.h

@@ -100,6 +100,8 @@ class HardwareSerial: public Stream
 
  size_t setRxBufferSize(size_t);
  void setDebugOutput(bool);
+ 
+ void setRxInvert(bool);
 
 protected:
  int _uart_nr;

cores/esp32/esp32-hal-uart.c

@@ -266,6 +266,17 @@ size_t uartResizeRxBuffer(uart_t * uart, size_t new_size) {
  return new_size;
 }
 
+void uartSetRxInvert(uart_t* uart, bool invert)
+{
+ if (uart == NULL)
+ return;
+ 
+ if (invert)
+ uart->dev->conf0.rxd_inv = 1;
+ else
+ uart->dev->conf0.rxd_inv = 0;
+}
+
 uint32_t uartAvailable(uart_t* uart)
 {
  if(uart == NULL || uart->queue == NULL) {

cores/esp32/esp32-hal-uart.h

@@ -70,6 +70,8 @@ uint32_t uartGetBaudRate(uart_t* uart);
 
 size_t uartResizeRxBuffer(uart_t* uart, size_t new_size);
 
+void uartSetRxInvert(uart_t* uart, bool invert);
+
 void uartSetDebug(uart_t* uart);
 int uartGetDebug();