tested and verified to work

Author: timkoers

cores/esp32/HardwareSerial.cpp

@@ -84,7 +84,7 @@ void HardwareSerial::updateBaudRate(unsigned long baud)
 }
 
 // Make sure that the function that the function pointer is pointing to is inside IRAM
-void HardwareSerial::setRXInterrupt(void (*arg)(char* c)){
+void HardwareSerial::setRXInterrupt(void (*arg)(char c)){
     uartDisableInterrupt(_uart);
     uartEnableInterrupt(_uart, &arg);
 }

cores/esp32/HardwareSerial.h

@@ -58,7 +58,7 @@ class HardwareSerial: public Stream
     void begin(unsigned long baud, uint32_t config=SERIAL_8N1, int8_t rxPin=-1, int8_t txPin=-1, bool invert=false, unsigned long timeout_ms = 20000UL);
     void end();
     void updateBaudRate(unsigned long baud);
-    void setRXInterrupt(void (*arg)(char* c));
+    void setRXInterrupt(void (*arg)(char));
     int available(void);
     int availableForWrite(void);
     int peek(void);

cores/esp32/esp32-hal-uart.c

@@ -69,7 +69,7 @@ static uart_t _uart_bus_array[3] = {
 
 static void uart_on_apb_change(void * arg, apb_change_ev_t ev_type, uint32_t old_apb, uint32_t new_apb);
 
-static void IRAM_ATTR _uart_isr(void *arg)
+static void IRAM_ATTR _uart_isr(void (*arg)(char))
 {
     uint8_t i, c;
     BaseType_t xHigherPriorityTaskWoken;
@@ -87,7 +87,7 @@ static void IRAM_ATTR _uart_isr(void *arg)
             c = uart->dev->fifo.rw_byte;
             if(arg != NULL){ // Check if an interrupt handler function has been specified
                 // Fully optimized code would not create the queue anymore if an function has been specified as an argument.
-                (*((void(**)())arg))(c); // There is, call it with c as an parameter. Don't pass it to the queue anymore
+                (*arg)((char*)&c); // There is, call it with c as an parameter. Don't pass it to the queue anymore
             }else if(uart->queue != NULL)  {
                 xQueueSendFromISR(uart->queue, &c, &xHigherPriorityTaskWoken);
             }
@@ -99,7 +99,7 @@ static void IRAM_ATTR _uart_isr(void *arg)
     }
 }
 
-void uartEnableInterrupt(uart_t* uart, void * func)
+void uartEnableInterrupt(uart_t* uart, void (*func)(char))
 {
     UART_MUTEX_LOCK();
     uart->dev->conf1.rxfifo_full_thrhd = 112;

cores/esp32/esp32-hal-uart.h

@@ -81,7 +81,7 @@ unsigned long uartDetectBaudrate(uart_t *uart);
 bool uartRxActive(uart_t* uart);
 
 void uartDisableInterrupt(uart_t* uart);
-void uartEnableInterrupt(uart_t* uart,void * func );
+void uartEnableInterrupt(uart_t* uart, void (*func)(char));
 
 #ifdef __cplusplus
 }

libraries/ESP32/examples/Serial/Interrupt/Interrupt.ino

@@ -1,19 +1,19 @@
 HardwareSerial hwSerial(0);
 HardwareSerial hwSerial2(2);
 
+static void IRAM_ATTR onSerialRX(char c){
+  hwSerial.print(c);
+}
+
 void setup()
 {
   hwSerial.begin(115200);
   hwSerial2.begin(115200);
-  hwSerial2.setRXInterrupt(onSerialRX);
+  hwSerial2.setRXInterrupt(&onSerialRX);
 
 }
 
 void loop()
 {
   delay(1);
 }
-
-void onSerialRX(char* c){
-  hwSerial.print(c);
-}