How to pass a class member function that modifies class members to a function that takes a function-CodePudding

I am writing software for an Arduino-powered weather station.

I have a class for each of the sensor systems (some simple, some complex) and the rain gauge one needs to use the Arduino attachInterrupt function.
Signature:

void attachInterrupt(uint8_t interruptNum, void (*userFunc)(), int mode)

This is used to execute a callback when a pin changes state, which increment a counter (which is a member variable of the class).

I currently have the following:

// `pulses` and `pin` are member variables.
void RainGauge::begin()
{
  pulses = 0;
  attachInterrupt(digitalPinToInterrupt(pin), callback, FALLING);
}

I need to somehow define that callback.

I have tried this, without success, due to the capturing aspect:

void RainGauge::begin()
{
  pulses = 0;
  auto callback = [this](void) {
    pulses  ;
  };
  attachInterrupt(digitalPinToInterrupt(pin), callback, FALLING);
}

This gives the error no suitable conversion function from "lambda []()->void" to "void (*)()" existsC/C (413).

Is there any way to do this?

CodePudding user response：

The problem is, on what object should the function be invoked when the interrupt occurs?

You could do it this way for example:

class RainGauge {
  int pulses;
public:
  void begin(int pin, void (*callback)());
  void increment();
};

void RainGauge::begin(int pin, void (*callback)())
{
  pulses = 0;
  attachInterrupt(digitalPinToInterrupt(pin), callback, FALLING);
}

void RainGauge::increment()
{
  pulses  ;
}

RainGauge RainGauge1;
RainGauge RainGauge2;

void setup() {
  RainGauge1.begin(2, []() {RainGauge1.increment()});
  RainGauge2.begin(3, []() {RainGauge2.increment()});
}

void loop() {

}