CODEWITHSUNDEEP
c++raspberry-pi-pico
tomdean1939
tomdean1939

Reputation: 41

How do I access member variables from a repeating timer callback

Using the RPI Pico SDK, I have three files. I want to use a callback function and access private members of a class. The callback function is in an SDK and I can not modify it. How do I do this?

/////// test.h
bool main_loop_timer_callback(struct repeating_timer *t);
class MyClass {
private:
    static int count;
    struct repeating_timer main_loop_timer;
public:
    MyClass();
    friend bool main_loop_timer_callback(struct repeating_timer *t);
};

//////// test.cc
#include <iostream>
#include "pico/stdlib.h"
#include "test.h"
using namespace std;
bool main_loop_timer_callback(struct repeating_timer *t) {
    MyClass::count++;
    cout << "callback " << MyClass::count << endl;
    return true;
}

MyClass::MyClass() {
    add_repeating_timer_us(-50000,
                           main_loop_timer_callback,
                           NULL,
                           &main_loop_timer);
    count = 0;
};

/////// test-main.cc
#include "pico/stdlib.h"
#include "test.h"
using namespace std;
int main() {
    MyClass test;
    stdio_init_all();
}

Upvotes: 0

Views: 835

Answers (1)

Hasturkun
Hasturkun

Reputation: 36412

The Pi Pico repeating_timer API allows you to pass a user_data argument when adding a timer (the third parameter to add_repeating_timer_us).

This value is later returned in the user_data member of the struct repeating_timer passed to your callback.

This can be anything you want, e.g. in your case, a pointer to MyClass, so long as you cast it to and from void *.

Upvotes: 1

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