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Cannot use attachInterrupt in library

I am writing a simple library for an ultrasonic distance sensor and I think that I will try to use interrupts.

However, I cannot correctly set my functions to attachCallback.

I want to HCSR04Interrupt::echoHigh(), and HCSR04Interrupt::echoLow()is called when the pin goes high and low, respectively.

I searched for this to no avail. The Ardiuno IDE says the following:

./Arduino/libraries/HCSR04/HCSR04Interrupt.cpp: In member function 'void HCSR04Interrupt::getDistance()':
./Arduino/libraries/HCSR04/HCSR04Interrupt.cpp:31: error: argument of type 'void (HCSR04Interrupt::)()' does not match 'void (*)()'
./Arduino/libraries/HCSR04/HCSR04Interrupt.cpp: In member function 'void HCSR04Interrupt::echoHigh()':
./Arduino/libraries/HCSR04/HCSR04Interrupt.cpp:47: error: argument of type 'void (HCSR04Interrupt::)()' does not match 'void (*)()'

Here is my headline:

#ifndef _HCSR04Interrupt_
#define _HCSR04Interrupt_

#include "Arduino.h"

#define HCSR04_CM_FACTOR 58.0
#define HCSR04_IN_FACTOR 148.0
#define HCSR04_CM_MODE 0
#define HCSR04_IN_MODE 1

class HCSR04Interrupt {
  public:
    double distance;

    HCSR04Interrupt(int trigger_pin, int echo_pin, void (*callback)());

    void setUnits(int units);

    void getDistance();
  private:
    int _trigger_pin;
    int _echo_pin;
    int _units;
    unsigned long _micros_start;
    void (*_callback)();

    void initialize();
    void echoHigh();
    void echoLow();
};

#endif

And my implementation (not complete, since I cannot pass the attachInterrupt step):

#include "Arduino.h"
#include "HCSR04Interrupt.h"

HCSR04Interrupt::HCSR04Interrupt(int trigger_pin, int echo_pin, void (*callback)()) {
  _trigger_pin = trigger_pin;
  _echo_pin = echo_pin;
  _callback = callback;

  initialize();
}

void HCSR04Interrupt::setUnits(int units) {
  _units = units;
}

void HCSR04Interrupt::initialize() {
  pinMode(_trigger_pin, OUTPUT);
  pinMode(_echo_pin, INPUT);

  digitalWrite(_trigger_pin, LOW);
}

void HCSR04Interrupt::getDistance() {
  //Listen for the RISING interrupt
  attachInterrupt(_echo_pin - 2, echoHigh, RISING);

  //The trigger pin should be pulled high,
  digitalWrite(_trigger_pin, HIGH);

  //for 10 us.
  delayMicroseconds(20);

  //Then reset it.
  digitalWrite(_trigger_pin, LOW);
}

void HCSR04Interrupt::echoHigh() {
  _micros_start = micros();

  detachInterrupt(_echo_pin - 2);
  attachInterrupt(_echo_pin - 2, echoLow, FALLING);
}

void HCSR04Interrupt::echoLow() {
  detachInterrupt(_echo_pin - 2);

  unsigned long us = micros() - _micros_start;

  distance = us;

  (*_callback)();
}
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4 answers

So, the compiler (and not the IDE) tells you exactly what is wrong:

argument of type 'void (HCSR04Interrupt::)()' does not match 'void (*)()

, attachInterrupt() void (*)(), -,, . - static :

static void echoHigh();

// ...

attachInterrupt(_echo_pin - 2, reinterpret_cast<void (*)()>(&echoHigh), RISING);
+5

Arduino . . , .

, , "" , . . , , , .

, echoHigh() echoLow() HCSR04Interrupt .

+2

, , , , :

. handleInterupt . . , . , . - , :

MyClass theInstance_pin3 = NULL;
MyClass theInstance_pin7 = NULL;

// Somewhere, fill in an initialized copy of MyClass,
// and set theInstance_pin3 or theInstance_pin7 to it

void ISR_3()
{
   if (theInstance_pin3)
       theInstance_pin3->handleInterrupt();
}
void ISR_7()
{
   if (theInstance_pin7)
       theInstance_pin7->handleInterrupt();
}

as a link: http://forum.arduino.cc/index.php?topic=41713.0 or http://forum.arduino.cc/index.php?topic=160101.0

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I went around this by creating a singleton base class, which is the hardware as a whole (which in any case makes sense in this situation).

Any function pointers can then be passed to the subcomponent class and processed by a singleton whose member variables and methods are all static.

Examples of headings (untested):

// Sub-component
class LampButton {
public:
    LampButton(int pin, void(*pushHandler)());
}

// Sub-component
class LampLed {
public:
    LampLed(int pin);
    void toggle();
}

// Singleton represents the hardware in it entirety
class Lamp {
public:
    // Call this instead of a constructor
    static void initialize(int buttonPin, int ledPin);

    // Function implemented inline for clarity - don't do this
    static void handleButtonPush() {
        led.toggle();
    }

private:
    static LampButton button;
    static LampLed led;
}
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