How to assign a class method as an interrupt handler?

maxgerhardt · April 5, 2021, 9:18pm

You’re going to have to implement something akin to what the people in the Arduino-ESP32 already do to enable abitrary lambdas and members functions as interrupts functions – use std::function.

For their implementation, see the FunctionalInterrupt.* files and examples.

github.com

espressif/arduino-esp32/blob/5502879a5b25e5fff84a7058f448be481c0a1f73/libraries/ESP32/examples/GPIO/FunctionalInterrupt/FunctionalInterrupt.ino#L10-L13


      
          	Button(uint8_t reqPin) : PIN(reqPin){
          		pinMode(PIN, INPUT_PULLUP);
          		attachInterrupt(PIN, std::bind(&Button::isr,this), FALLING);
          	};

github.com

espressif/arduino-esp32/blob/5502879a5b25e5fff84a7058f448be481c0a1f73/cores/esp32/FunctionalInterrupt.cpp#L19-L32


      
          void ARDUINO_ISR_ATTR interruptFunctional(void* arg)
          {
              InterruptArgStructure* localArg = (InterruptArgStructure*)arg;
          	if (localArg->interruptFunction)
          	{
          	  localArg->interruptFunction();
          	}
          }
          
          
void attachInterrupt(uint8_t pin, std::function<void(void)> intRoutine, int mode)
          {
          	// use the local interrupt routine which takes the ArgStructure as argument
          	__attachInterruptFunctionalArg (pin, (voidFuncPtrArg)interruptFunctional, new InterruptArgStructure{intRoutine}, mode, true);
          }

github.com

espressif/arduino-esp32/blob/5502879a5b25e5fff84a7058f448be481c0a1f73/cores/esp32/FunctionalInterrupt.h#L11-L17


      
          #include <functional>
          
          
struct InterruptArgStructure {
          	std::function<void(void)> interruptFunction;
          };
          
          
void attachInterrupt(uint8_t pin, std::function<void(void)> intRoutine, int mode);

The base ISR function must be a static void function with no arguments, not a member function of the class. However, you can store the to be called function expression in a std::function and call into that object later, just like their implementation does.