Class member function as callback for interrupt

Projects Programming
25

There's a fairly elegant way to have instance-specific ISRs using a table of instance pointers and some template trickery:

// ------------------------------ Define the Number of Interrupts Available for Various Boards ------------------
// Teensy (and maybe others) define these automatically
#if !defined(CORE_NUM_INTERRUPT)

// Arduino Uno
#if defined(__AVR_ATmega328P__)
#define CORE_NUM_INTERRUPT  2

// Arduino Mega
#elif defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
#define CORE_NUM_INTERRUPT  6

// ESP32
#elif defined(ESP32)
#define CORE_NUM_INTERRUPT  40

#endif
#endif
// ------------------------------ Add More Boards as Necessary ------------------



#if !defined(CORE_NUM_INTERRUPT)
#error CORE_NUM_INTERRUPT Not Defined!!!
#endif

class Motor {
  public:
    Motor(uint8_t p): pinEncA(p) {};
    ~Motor() {
      if(intAttached) {
        detachInterrupt(interruptNum);
      }
    }
    bool begin();

  private:
    int interruptNum {-1};
    bool intAttached {false};
    using isrFunct = void (*)();
    static Motor *objectTable[CORE_NUM_INTERRUPT];
    uint8_t pinEncA;
    void cbkEncA ();

    template<uint8_t NUM_INTERRUPTS = CORE_NUM_INTERRUPT>
    static isrFunct getIsr(uint8_t intNumber);
};

Motor * Motor::objectTable[CORE_NUM_INTERRUPT];

template<uint8_t NUM_INTERRUPTS>
Motor::isrFunct Motor::getIsr(uint8_t intNumber) {
  if (intNumber == (NUM_INTERRUPTS - 1)) {
    return [] {
      (objectTable[NUM_INTERRUPTS - 1])->cbkEncA();
    };
  }
  return getIsr < NUM_INTERRUPTS - 1 > (intNumber);
}

template<>
inline Motor::isrFunct Motor::getIsr<0>(uint8_t intNum) {
  (void) intNum;
  return nullptr;
}

bool Motor::begin() {
  pinMode(pinEncA, INPUT_PULLUP);
  intAttached = false;
  interruptNum = digitalPinToInterrupt(pinEncA);
  if ((interruptNum < 0) || (interruptNum >= CORE_NUM_INTERRUPT)) {
    return false;
  }
  isrFunct isr {getIsr(interruptNum)};
  if (isr == nullptr) {
    return false;
  }
  objectTable[interruptNum] = this;
  attachInterrupt(interruptNum, isr, RISING);
  intAttached = true;
  return true;
}

// Instance-specific ISR Here
void Motor::cbkEncA() {
}

Motor motor(3);

void setup() {
  Serial.begin(115200);
  delay(1000);
  if (!motor.begin()) {
    Serial.println("Attach Interrupt Failed");
    while (1) {}
  }
  Serial.println("Attached");
}

void loop() {


}