Call Ticker library from another class

Using Arduino Programming Questions
#1

Hi, there.

I’m creating a library, and would like to make use of the Ticker library from it. But apparently the function attach (from the Ticker library) expects a callback into another function. It works fine from a sketch. But how do I pass this on from another library? What is the syntax for doing this from a class?

This is a part of my header file:

#ifndef konnec_h
#define konnec_h

#include "Arduino.h"

#define ledB 12

class Ticker;

class Konnec {
public:
  void openAP();
  void begin();

private:
   Ticker *_ticker = NULL;
    void tick();
}

And this is part of my .cpp file:

#include <konnec.h>
#include "Arduino.h"
#include <Ticker.h>

void Konnec::begin() {
        _ticker = new Ticker();
}

void Konnec::tick() {    //This is the funcion I'd like to Ticker library to execute
	//toggle state
	byte state = digitalRead(ledB);
	digitalWrite(ledB, !state);
}

void Konnec::openAP() {    //This is the function where I'd to attach the ticker
       _ticker->attach(0.6, tick);
}

This is the error I get:

Compiling 'HomeCenter_v20' for 'NodeMCU 1.0 (ESP-12E Module)'
konnec.cpp:In member function 'void Konnec::openAP()
konnec.cpp:141:27: error: no matching function for call to 'Ticker::attach(double, <unresolved overloaded function type>)
:_ticker->attach(0.6, tick)
konnec.cpp:candidates are
konnec.cpp:In file included from
Ticker.h:callback_t)
:void attach(float seconds, callback_t callback)
Ticker.h:callback_t {aka void (*)()}
Ticker.h:attach(float, void (*)(TArg), TArg)
:void attach(float seconds, void (*callback)(TArg), TArg arg)
Ticker.h:template argument deduction\substitution failed
konnec.cpp:*)()
:_ticker->attach(0.6, tick)
konnec.cpp:tick
Error compiling libraries

But if I change the implementation to:

void Konnec::openAP() {    //This is the function where I wanna attach the ticker
       _ticker->attach(0.6, tick());
}

I get this error:

Compiling 'HomeCenter_v20' for 'NodeMCU 1.0 (ESP-12E Module)'
konnec.cpp:In member function 'void Konnec::openAP()
konnec.cpp:141:29: error: invalid use of void expression
:_ticker->attach(0.6, tick())
Error compiling libraries

Can anybody please help? :slight_smile:

#2

cimd:
This is a part of my header file:

This is a part of my answer:

All you need to do is gr

#3

The method in the class that you want to use a callback function must be declared as a static method.

Otherwise, when the callback needs to be called, the Ticker class has no idea which instance of your class should have it's tick() method called.

#4

You're brilliant, PaulS. Worked like a charm!

#5

Is there really no way to call any register the callback from any of the Ticker libraries to call a method on a class?

I haven't used C++ since its had lambdas. In Swift, this would be trivial, but I haven't figured out the syntax here. Can the callback be a lambda that's closing over 'this' to have it reference a method on an object.

Thanks

#6

dm33:
Is there really no way to call any register the callback from any of the Ticker libraries to call a method on a class?

I haven't used C++ since its had lambdas. In Swift, this would be trivial, but I haven't figured out the syntax here. Can the callback be a lambda that's closing over 'this' to have it reference a method on an object.

Thanks

Your question seems to be missing at least one word. I can't figure out which word is missing, so I can't make sense of the question.

Suppose that you have 8 instances of the Ticker class. A timer goes off. Which instance cares?

When you can answer that question, then the solution becomes trivial to implement.

#7