How to fix compilation error for tone() using same timer as other function

Question

I am trying to integrate tone() with the open source program for the Amped heart rate monitor. The error:

Tone.cpp.o (symbol from plugin): In function `timer0_pin_port':

(.text+0x0): multiple definition of `__vector_7'

sketch\PulseSensorAmped_Arduino_1dot4.ino.cpp.o (symbol from plugin):(.text+0x0): first defined here

The program comes in three files. PulseSensorAmped_Arduino_1dot4.cpp I don't think references any timers but references a function in another file with this code:

 // Initializes Timer2 to throw an interrupt every 2mS.
 TCCR2A = 0x02; // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
 TCCR2B = 0x06; // DON'T FORCE COMPARE, 256 PRESCALER 
 OCR2A = 0X7C; // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
 TIMSK2 = 0x02; // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
 sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED

This uses timer 2; but isn't the error for timer 1? The tone() reference page says that tone interferes with pins 3 and 11. Is there any way to fix this?

references:

https://www.arduino.cc/en/Reference/Tone

https://github.com/WorldFamousElectronics/PulseSensor_Amped_Arduino

• brasofilo: In my case, IR library was conflicting with Tone. Nick's solution works perfectly.

Answer 1

It looks like the Tone library uses Timer 2, and it looks like your other code also uses Timer 2, hence the error message. Vector 7 would be the TIMER2_COMPA_vect (Timer 2 compare "a").

Pins 3 and 11 are from Timer 2.

I wrote a small library that generates tones using the hardware PWM and not interrupts. You can read about it here.

Example code:

#include <TonePlayer.h>
TonePlayer tone1 (TCCR1A, TCCR1B, OCR1AH, OCR1AL, TCNT1H, TCNT1L); // pin D9 (Uno), D11 (Mega)
void setup() 
 {
 pinMode (9, OUTPUT); // output pin is fixed (OC1A)
 tone1.tone (220); // 220 Hz
 delay (500);
 tone1.noTone ();
 tone1.tone (440);
 delay (500);
 tone1.noTone ();
 tone1.tone (880);
 delay (500);
 tone1.noTone ();
 }
void loop() { }

Library can be downloaded from http://www.gammon.com.au/Arduino/TonePlayer.zip

This uses Timer 1 (so that won't interfere with Timer 2) and no interrupts.

• brasofilo: For anyone wondering, when defining a tone, all those codes seem to be the address of the single workable pin on Uno/Mega (pin 9). For Mega 2560 there are 3 different pins and TonePlayer.cpp file has the examples.
• Nick Gammon: That's true, thanks for the clarification. In the source are examples of choosing between 3 pins (which are the outputs of the three hardware timers).