Problem with interrupt inside a class

Projects Programming
1

Hey everyone,

I am having an issue with my code. I'm not a programming nor C++ expert by any stretch of imagination so please be patient :smiley:

My goal is to create a class that can handle an interrupt on an Arduino Nano. By researching this on the internet, I found out, that I would need to create an interrupt handler as a static method of the class.

My main.cpp looks like this:

#include <Arduino.h>
#include "interruptClass.h"

static const int interrupt_pin = 2;

interruptClass myInterruptClass(interrupt_pin);

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println(myInterruptClass.getCounter());
}

My interruptClass header file looks like this:

#pragma once

#include <Arduino.h>

class interruptClass
{
    public:
        interruptClass(int interrupt_pin);
        unsigned long getCounter();
    private:
        static void interruptHandler();
        void increment();
        int m_interrupt_pin;
        volatile unsigned long m_counter = 0;
};

My interruptClass.cpp looks like this:

#include "interruptClass.h"

interruptClass::interruptClass(int interrupt_pin):
m_interrupt_pin(interrupt_pin)
{
    pinMode(m_interrupt_pin, INPUT);
    attachInterrupt(digitalPinToInterrupt(m_interrupt_pin), interruptClass::interruptHandler, RISING);
}

void interruptClass::interruptHandler()
{
    static interruptClass *instance = nullptr;
    if (instance)
    {
        instance->increment();
    }
}

void interruptClass::increment()
{
    m_counter++;
}

unsigned long interruptClass::getCounter()
{
    return m_counter;
}

However, the interrupt does not trigger. What am I doing wrong?

Thank you very much!

2

I not seen where you assign anything to your instance pointer.

3

You should not do hardware related stuff in your constructor. Add a begin method to the class where you set the pinMode and attach the interrupt.

4

@b707 How would I do it correctly? I have never before worked with something like this and the code from the interruptHandler is right out of ChatGPT :smiley:

@sterretje Thank you for your hint! I created a public begin function that is being called in the setup part of the main.cpp. However this didn't resolve the issue.

5

I would move the instanse variable to the class definition instead the method and add

instance = this;

to the constructor.

6

I added the following to the private members of the class:

static interruptClass *instance;

Then, I added the line

instance = this;

to the constructor in between the braces.

The content of the interruptHandler method is now reduced to:

instance->increment();

However, if I want to compile, I get the following error:

C:\Users\User\AppData\Local\Temp\ccbcijcg.ltrans0.ltrans.o: In function interruptClass::interruptHandler()': <artificial>:(.text+0x21e): undefined reference to interruptClass::instance'
:(.text+0x222): undefined reference to interruptClass::instance' C:\Users\User\AppData\Local\Temp\ccbcijcg.ltrans0.ltrans.o: In function global constructors keyed to 65535_0_interruptClass.cpp.o.1788':
:(.text.startup+0x6e): undefined reference to interruptClass::instance' <artificial>:(.text.startup+0x72): undefined reference to interruptClass::instance'
collect2.exe: error: ld returned 1 exit status
*** [.pio\build\nanoatmega328\firmware.elf] Error 1

7

You need to start with the understanding that any code you get from ChatGPT (or instructables.com) is going to be crap.

For a more general method of handling interrupts in classes, see Post #44 in this Thread.

8

Why did you decided to make it private?

9

I followed this approach, which is pretty similar and now it works fine! Thank you guys very much for your help!

10

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