Calling a function that is outside of a class from inside

Question

I have an Arduino sketch with a timer interrupt class and would like to place the TIMER2Services() function in the TimerTwoTest.ino file for easy access. On compile I get a multiple definition of tmb2 error in the .ino TIMER2Services() function. I have tried all the variations I can think of but no luck. Is there a way to do this?

TimerTwoTest.cpp.o: In function `TIMER2Services()':
D:\Arduino157/TimerTwoTest.ino:41: multiple definition of `tmb2'
TimerTwo.cpp.o:C:\Users\...\build8577138580185682113.tmp/TimerTwo.cpp:10: first defined here

collect2.exe:

TimerTwo.h:

class Tmb2
{
 public:
 void initTIMER2(unsigned int Hz, unsigned int ulPeriod);
 void resetTIMER2(unsigned int Hz, unsigned int ulPeriod);
 TIMER2_TYPE getPeriodTIMER2(void);
 void activeTIMER2 (void);
 private:
}tmb2;

TimerTwo.cpp:

extern void TIMER2Services(void);
[this function is line 10 for the error]
void Tmb2::initTIMER2(unsigned int Hz, unsigned int ulPeriod){ //setperiod and enable interrupt
 if (Hz){
 ulPeriod = 1000/Hz; //if Hz > 0 use frequency microseconds
 }
 Timer2.attachInterrupt(TIMER2Services).setPeriod(ulPeriod).start();
}

TimerTwoTest.ino:

volatile unsigned long burpCount = 0;
//This routine services the interrupt
void TIMER2Services(void){
 burpCount++;
}

• Anonymous Penguin: Which file(s) are you including, and where? Also: it looks like you're using an external library: is this correct?

Answer 1

The problem is your definition of tmb2. You're declaring the variable in the header file, and not the C(++) file.

Please try this:

TimerTwo.h

#ifndef __TIMER_TWO_H__
#define __TIMER_TWO_H__
extern void TIMER2Services(void);
class Tmb2
{
 public:
 void initTIMER2(unsigned int Hz, unsigned int ulPeriod);
 void resetTIMER2(unsigned int Hz, unsigned int ulPeriod);
 TIMER2_TYPE getPeriodTIMER2(void);
 void activeTIMER2 (void);
 private:
};
#endif // #ifndef __TIMER_TWO_H__

The #ifndef TIMER stuff saves you getting multiple definitions from header files if they're included more than once. There's other ways to do this, but this is simple and well-known.

TimerTwo.cpp

#include "TimerTwo.h"
void Tmb2::initTIMER2(unsigned int Hz, unsigned int ulPeriod)
{ 
 //setperiod and enable interrupt
 if (Hz)
 {
 ulPeriod = 1000/Hz; //if Hz > 0 use frequency microseconds
 }
 Timer2.attachInterrupt(TIMER2Services).setPeriod(ulPeriod).start();
}

TimerTwoTest.ino

#include "TimerTwo.h"
Tmb2 tmb2;
volatile unsigned long burpCount = 0;
// This routine services the interrupt
void TIMER2Services(void)
{
 burpCount++;
}
void setup()
{
 tmb2.initTIMER2(blah1,blah2);
}

For the sake of neatness, I'd move TIMER2Services into class Tmb2 as a static function... if possible.

• Gerben: Shouldn't TimerTwo tmb2; be Tmb2 tmb2;?
• Kingsley: Yeah, you're right Gerben. I've just edited it
• CharlieHanson: I would also re-think the closeness of the class name and instantiation name: Tmb2 looks very much like tmb2, and could lead to errors of mistaken identity. It's certainly a personal 'good practice' for me, but there are no rules for either opinions.