adds Hardware Flow Control mode and CTS/RTS pin setting

Author: SuGlider

cores/esp32/HardwareSerial.cpp

@@ -301,6 +301,12 @@ void HardwareSerial::setAllPins(int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_
     uartSetPins(_uart, rxPin, txPin, ctsPin, rtsPin);
 }
 
+// Enables or disables Hardware Flow Control using RTS and/or CTS pins (must use setAllPins() before)
+void HardwareSerial::setHwFlowCtrlMode(uint8_t mode, uint8_t threshold)
+{
+    uartSetHwFlowCtrlMode(_uart, mode, threshold);
+}
+
 size_t HardwareSerial::setRxBufferSize(size_t new_size) {
 
     if (_uart) {

cores/esp32/HardwareSerial.h

@@ -110,9 +110,11 @@ class HardwareSerial: public Stream
 
     // Negative Pin Number will keep it unmodified, thus this function can set individual pins
     // SetPins shall be called after Serial begin()
-    void setPins(int8_t rxPin, int8_t txPin);
-    void setAllPins(int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin);
-    
+    void setPins(int8_t rxPin = -1, int8_t txPin = -1);
+    void setAllPins(int8_t rxPin = -1, int8_t txPin = -1, int8_t ctsPin = -1, int8_t rtsPin = -1);
+    // Enables or disables Hardware Flow Control using RTS and/or CTS pins (must use setAllPins() before)
+    void setHwFlowCtrlMode(uint8_t mode = HW_FLOWCTRL_CTS_RTS, uint8_t threshold = 64);   // 64 is half FIFO Length
+
     size_t setRxBufferSize(size_t new_size);
 
 protected:

cores/esp32/esp32-hal-uart.c

@@ -168,6 +168,16 @@ void uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t
     UART_MUTEX_UNLOCK();  
 }
 
+// 
+void uartSetHwFlowCtrlMode(uart_t *uart, uint8_t mode, uint8_t threshold) {
+    if(uart == NULL) {
+        return;
+    }
+    // IDF will issue corresponding error message when mode or threshold are wrong and prevent crashing
+    // IDF will check (mode > HW_FLOWCTRL_CTS_RTS || threshold >= SOC_UART_FIFO_LEN)
+    uart_set_hw_flow_ctrl(uart->num, (uart_hw_flowcontrol_t) mode, threshold);
+}
+
 
 uart_t* uartBegin(uint8_t uart_nr, uint32_t baudrate, uint32_t config, int8_t rxPin, int8_t txPin, uint16_t queueLen, bool inverted, uint8_t rxfifo_full_thrhd)
 {

cores/esp32/esp32-hal-uart.h

@@ -48,6 +48,14 @@ extern "C" {
 #define SERIAL_7O2 0x800003b
 #define SERIAL_8O2 0x800003f
 
+// These are Hardware Flow Contol possible usage
+// equivalent to UDF enum uart_hw_flowcontrol_t from 
+// https://github.com/espressif/esp-idf/blob/master/components/hal/include/hal/uart_types.h#L75-L81
+#define HW_FLOWCTRL_DISABLE   0x0       // disable HW Flow Control
+#define HW_FLOWCTRL_RTS       0x1       // use only RTS PIN for HW Flow Control
+#define HW_FLOWCTRL_CTS       0x2       // use only CTS PIN for HW Flow Control
+#define HW_FLOWCTRL_CTS_RTS   0x3       // use both CTS and RTS PIN for HW Flow Control
+
 struct uart_struct_t;
 typedef struct uart_struct_t uart_t;
 
@@ -80,6 +88,9 @@ bool uartIsDriverInstalled(uart_t* uart);
 // Negative Pin Number will keep it unmodified, thus this function can set individual pins
 void uartSetPins(uart_t* uart, int8_t rxPin, int8_t txPin, int8_t ctsPin, int8_t rtsPin);
 
+// Enables or disables HW Flow Control function -- needs also to set CTS and/or RTS pins
+void uartSetHwFlowCtrlMode(uart_t *uart, uint8_t mode, uint8_t threshold);
+
 void uartStartDetectBaudrate(uart_t *uart);
 unsigned long uartDetectBaudrate(uart_t *uart);