TimerFreeTone.cpp

// ---------------------------------------------------------------------------
// Created by Tim Eckel - teckel@leethost.com
// Copyright 2016 License: GNU GPL v3 http://www.gnu.org/licenses/gpl-3.0.html
//
// See "TimerFreeTone.h" for purpose, syntax, version history, links, and more.
// ---------------------------------------------------------------------------

#include "TimerFreeTone.h"

uint8_t _tft_volume[] = { 255, 200, 150, 125, 100, 87, 50, 33, 22, 2 }; // Duty for linear volume control.

void TimerFreeTone(uint8_t pin, unsigned long frequency, unsigned int duration, uint8_t volume) {
	if (frequency == 0 || volume == 0) { // If frequency or volume are zero, just wait duration and exit.
		delay(duration);
		return;
	} 
	frequency = 1000000 / frequency;                              // Calculate the square wave length (in microseconds).
	uint32_t duty = frequency / _tft_volume[min(volume, 10) - 1]; // Calculate the duty cycle (volume).
#ifdef __AVR__
	uint8_t pinBit = digitalPinToBitMask(pin);                                  // Get the bitmask for the pin.
	volatile uint8_t *pinOutput = (uint8_t *) portOutputRegister(digitalPinToPort(pin)); // Get the port register for the pin.
	volatile uint8_t *portMode = (uint8_t *) portModeRegister(digitalPinToPort(pin));    // Get the port mode register for the pin.
	*portMode |= pinBit;                                                        // Set pin to output mode.
#else
	pinMode(pin, OUTPUT);                                                       // Set pin to output mode.
#endif

	uint32_t startTime = millis();           // Starting time of note.
	while(millis() - startTime < duration) { // Loop for the duration.
	#ifdef __AVR__
		*pinOutput |= pinBit;    // Set pin high.
		delayMicroseconds(duty); // Square wave duration (how long to leave pin high).
		*pinOutput &= ~pinBit;   // Set pin low.
	#else
		digitalWrite(pin,HIGH);  // Set pin high.
		delayMicroseconds(duty); // Square wave duration (how long to leave pin high).
		digitalWrite(pin,LOW);   // Set pin low.
	#endif
		delayMicroseconds(frequency - duty); // Square wave duration (how long to leave pin low).
	}
}