Accessing HardwareTimer Object in different file

Hello Girls and Guys,

i am quite new to programming real C++ and only did Arduino before.

I read the “tutorial” about splitting C++ code in different files and sucsessfully implemented it so far.
However i cant get the HardwareTimers to work.

In Main.cpp i do:

#Include <Arduino.h>
HardwareTimer *Tim1 = new HardwareTimer(TIM1); 

and so on, no problem everything works.

If i now want to have a function in a different file say:
In function.cpp i do:

#Include <Arduino.h>

Doesnt work, makes sense, compiler doesnt know what Tim1 is because its not declared there.
I tried:
In main.h i do:

class Tim1; 

Together with including main.h in function.cpp.

Didnt work.
What i want to do is set a PWM value from mutiple different functions, so i would need to have access to Tim1 from multiple functions.
I tried to extern Tim1 but that also didnt work.

I am struggeling to understand what Tim1 actually is. A Pointer to a object?
I do something wrong which is very obvius for people fluent in C++.

Thanks for Helping!

In your other source files, which need to access Tim1, simply add one line:

extern HardwareTimer *Tim1;

You might need to add a line above that, if the header for the HardwareTimer library hasn’t been included:

class HardwareTimer;
extern HardwareTimer *Tim1;

Try those.



1 Like

Thanks, that worked flawlessly.

Thats forward declaration right?

I am still having a different but very similar issue.
I made a Class that i use to generate eeprom storage objects. Its quite simple:


class EEPROM_RW{
    int Adress;
    bool type;
    int Value;
    int ValueOld;
    EEPROM_RW(bool ObjType);
    int Read();
    bool NeedsSaving();
    void Set(int NewValue);
    void Save();


    EEPROM_RW::EEPROM_RW(bool ObjType){ 
      Adress = Used_Adresses;
      type = ObjType; 
    int EEPROM_RW::Read(){
        return Value;

    bool EEPROM_RW::NeedsSaving(){
    //return stuff

    void EEPROM_RW::Save(){
    //save stuff

How would i go about using a class member in a different file?
I cant figure out how i need to do the ?forward declaration?.
Maybe i am just missing a keyword to google.

In the main file, create your main member of the class, call it eerw.

In the different file, declare an extern EEPROM_RW eerw to match the one in the main file. Alternatively, a pointer to a class, if that’s how it’s defined in the top level.

You will most likely also need to include the header file for the class.

Then either:


// Or, for a pointer if eerw is one.

eerw->function (parameters);