# Tone Function Arduino

Hello, I am trying to understand how the Tone Function on Arduino works. This function allows you to interface a buzzer at certain frequency.

``````// frequency (in hertz) and duration (in milliseconds).

void tone(uint8_t _pin, unsigned int frequency, unsigned long duration)
{
uint8_t prescalarbits = 0b001;
long toggle_count = 0;
uint32_t ocr = 0;
int8_t _timer;

_timer = toneBegin(_pin);

if (_timer >= 0)
{
// Set the pinMode as OUTPUT
pinMode(_pin, OUTPUT);

// if we are using an 8 bit timer, scan through prescalars to find the best fit
if (_timer == 0 || _timer == 2)
{
ocr = F_CPU / frequency / 2 - 1;
prescalarbits = 0b001;  // ck/1: same for both timers
if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 8 - 1;
prescalarbits = 0b010;  // ck/8: same for both timers

if (_timer == 2 && ocr > 255)
{
ocr = F_CPU / frequency / 2 / 32 - 1;
prescalarbits = 0b011;
}

if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 64 - 1;
prescalarbits = _timer == 0 ? 0b011 : 0b100;

if (_timer == 2 && ocr > 255)
{
ocr = F_CPU / frequency / 2 / 128 - 1;
prescalarbits = 0b101;
}

if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 256 - 1;
prescalarbits = _timer == 0 ? 0b100 : 0b110;
if (ocr > 255)
{
// can't do any better than /1024
ocr = F_CPU / frequency / 2 / 1024 - 1;
prescalarbits = _timer == 0 ? 0b101 : 0b111;
}
}
}
}

#if defined(TCCR0B)
if (_timer == 0)
{
TCCR0B = (TCCR0B & 0b11111000) | prescalarbits;
}
else
#endif
#if defined(TCCR2B)
{
TCCR2B = (TCCR2B & 0b11111000) | prescalarbits;
}
#else
{
// dummy place holder to make the above ifdefs work
}
#endif
}
else
{
// two choices for the 16 bit timers: ck/1 or ck/64
ocr = F_CPU / frequency / 2 - 1;

prescalarbits = 0b001;
if (ocr > 0xffff)
{
ocr = F_CPU / frequency / 2 / 64 - 1;
prescalarbits = 0b011;
}

if (_timer == 1)
{
#if defined(TCCR1B)
TCCR1B = (TCCR1B & 0b11111000) | prescalarbits;
#endif
}
#if defined(TCCR3B)
else if (_timer == 3)
TCCR3B = (TCCR3B & 0b11111000) | prescalarbits;
#endif
#if defined(TCCR4B)
else if (_timer == 4)
TCCR4B = (TCCR4B & 0b11111000) | prescalarbits;
#endif
#if defined(TCCR5B)
else if (_timer == 5)
TCCR5B = (TCCR5B & 0b11111000) | prescalarbits;
#endif

}

// Calculate the toggle count
if (duration > 0)
{
toggle_count = 2 * frequency * duration / 1000;
}
else
{
toggle_count = -1;
}

// Set the OCR for the given timer,
// set the toggle count,
// then turn on the interrupts
switch (_timer)
{

#if defined(OCR0A) && defined(TIMSK0) && defined(OCIE0A)
case 0:
OCR0A = ocr;
timer0_toggle_count = toggle_count;
bitWrite(TIMSK0, OCIE0A, 1);
break;
#endif

case 1:
#if defined(OCR1A) && defined(TIMSK1) && defined(OCIE1A)
OCR1A = ocr;
timer1_toggle_count = toggle_count;
bitWrite(TIMSK1, OCIE1A, 1);
#elif defined(OCR1A) && defined(TIMSK) && defined(OCIE1A)
// this combination is for at least the ATmega32
OCR1A = ocr;
timer1_toggle_count = toggle_count;
bitWrite(TIMSK, OCIE1A, 1);
#endif
break;

#if defined(OCR2A) && defined(TIMSK2) && defined(OCIE2A)
case 2:
OCR2A = ocr;
timer2_toggle_count = toggle_count;
bitWrite(TIMSK2, OCIE2A, 1);
break;
#endif

#if defined(OCR3A) && defined(TIMSK3) && defined(OCIE3A)
case 3:
OCR3A = ocr;
timer3_toggle_count = toggle_count;
bitWrite(TIMSK3, OCIE3A, 1);
break;
#endif

#if defined(OCR4A) && defined(TIMSK4) && defined(OCIE4A)
case 4:
OCR4A = ocr;
timer4_toggle_count = toggle_count;
bitWrite(TIMSK4, OCIE4A, 1);
break;
#endif

#if defined(OCR5A) && defined(TIMSK5) && defined(OCIE5A)
case 5:
OCR5A = ocr;
timer5_toggle_count = toggle_count;
bitWrite(TIMSK5, OCIE5A, 1);
break;
#endif

}
}
}
``````

It realies in this other function:

``````static int8_t toneBegin(uint8_t _pin)
{
int8_t _timer = -1;

// if we're already using the pin, the timer should be configured.
for (int i = 0; i < AVAILABLE_TONE_PINS; i++) {
if (tone_pins[i] == _pin) {
}
}

// search for an unused timer.
for (int i = 0; i < AVAILABLE_TONE_PINS; i++) {
if (tone_pins[i] == 255) {
tone_pins[i] = _pin;
break;
}
}

if (_timer != -1)
{
// Set timer specific stuff
// All timers in CTC mode
// 8 bit timers will require changing prescalar values,
// whereas 16 bit timers are set to either ck/1 or ck/64 prescalar
switch (_timer)
{
#if defined(TCCR0A) && defined(TCCR0B) && defined(WGM01)
case 0:
// 8 bit timer
TCCR0A = 0;
TCCR0B = 0;
bitWrite(TCCR0A, WGM01, 1);
bitWrite(TCCR0B, CS00, 1);
timer0_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif

#if defined(TCCR1A) && defined(TCCR1B) && defined(WGM12)
case 1:
// 16 bit timer
TCCR1A = 0;
TCCR1B = 0;
bitWrite(TCCR1B, WGM12, 1);
bitWrite(TCCR1B, CS10, 1);
timer1_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif

#if defined(TCCR2A) && defined(TCCR2B)
case 2:
// 8 bit timer
TCCR2A = 0;
TCCR2B = 0;
bitWrite(TCCR2A, WGM21, 1);
bitWrite(TCCR2B, CS20, 1);
timer2_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif

#if defined(TCCR3A) && defined(TCCR3B) &&  defined(TIMSK3)
case 3:
// 16 bit timer
TCCR3A = 0;
TCCR3B = 0;
bitWrite(TCCR3B, WGM32, 1);
bitWrite(TCCR3B, CS30, 1);
timer3_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif

#if defined(TCCR4A) && defined(TCCR4B) &&  defined(TIMSK4)
case 4:
// 16 bit timer
TCCR4A = 0;
TCCR4B = 0;
#if defined(WGM42)
bitWrite(TCCR4B, WGM42, 1);
#elif defined(CS43)
// TODO this may not be correct
// atmega32u4
bitWrite(TCCR4B, CS43, 1);
#endif
bitWrite(TCCR4B, CS40, 1);
timer4_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif

#if defined(TCCR5A) && defined(TCCR5B) &&  defined(TIMSK5)
case 5:
// 16 bit timer
TCCR5A = 0;
TCCR5B = 0;
bitWrite(TCCR5B, WGM52, 1);
bitWrite(TCCR5B, CS50, 1);
timer5_pin_port = portOutputRegister(digitalPinToPort(_pin));
break;
#endif
}
}

return _timer;
}
``````

Does anyone know what does is this function doing? How it works? I am trying to code something simmilar in a PIC Microcotroller

I've never used a PIC chip, but every microcontroller has a different architecture and there are several different PIC chips.

High level languages like C++ isolate you from the hardware details but with microcontroller programming you're not using Standard ANSI/ISO C/C++ so the language functions and details are different depending on the chip.

What kind of timing functions does your PIC chip have? If there is a timer interrupt you can use that. (It might require Assembly Language.)

Yes, it has a Timer Interrupt ... I only need to know the signal that I have to generate ...

It's a very simple signal as tone() just produces a square wave at the specified frequency.

Steve

So .. I can do it with PWM with a duty cycle of 50% and the specified frequency

DelfinDelfin:
So .. I can do it with PWM with a duty cycle of 50% and the specified frequency

If you can fix the duty cycle then changing the frequency of the PWM will change the tone.
BUT
Simply changing the frequency of the PWM clock will also change the duty cycle so you have to adjust two register values in the timer, the count and the threshold.

Hi, I would like to ask you for a help ... I have to present a work day 6, and I'm going to use a buzzer, but I wanted something nice and I do not know how to do code for arduino music ... I wanted someone to do it the code for my presentation, the ideal is the library tone because it will save me a lot of having to redo my code ... this is the music I wanted to do a funny thing, it's just to make the chorus

I wanted someone to do it the code for my presentation

Then you need to post in the Gigs and Collaboration section. It is best if you say how much you are willing to pay as well.