My halloween project (PIR triggered sounds)

halloween.cpp

#include "Arduino.h"

#define PIR_INPUT 11
#define DFPLAYER_OUTPUT 10
#define WAIT_TICKS_INTERVAL 1000 // each ticks is about 10ms


int ledPin = 13;    // LED connected to digital pin 13
uint8_t state = 0;
volatile uint32_t ticks;
uint32_t lastTrigger;


ISR(TIMER0_COMPA_vect, ISR_BLOCK) {
	ticks++;
}

void init_systicks() {

	TCCR0B = _BV(CS02) | _BV(CS00);
	TCCR0A = _BV(WGM01);
	TIMSK0 = _BV(OCIE0A);

	// 8000000/1024/78 == 100HZ -> 10 ms
	OCR0A = 77; // !!! must me set last or it will not work!
}

uint32_t math_calc_diff(uint32_t value1, uint32_t value2) {
	if (value1 == value2) {
		return 0;
	}
	if (value1 > value2) {
		return (value1 - value2);
	}
	else {
		// check for overflow
		return (0xffffffff - value2 + value1);
	}
}

void delay_ticks(uint16_t t) {
	uint32_t now_ticks = ticks;
	while(math_calc_diff(ticks, now_ticks) < t) {
		// do nothing
	}
}

// The setup() method runs once, when the sketch starts
void setup() {
	init_systicks();

	Serial.begin(38400);
	// initialize the digital pin as an output:
	pinMode(ledPin, OUTPUT);
	pinMode(PIR_INPUT, INPUT);
	pinMode(DFPLAYER_OUTPUT, OUTPUT);
	digitalWrite(DFPLAYER_OUTPUT, HIGH);
}

// the loop() method runs over and over again,
// as long as the Arduino has power

void loop() {

	if (digitalRead(PIR_INPUT) == HIGH) {
		digitalWrite(ledPin, HIGH);


		if (math_calc_diff(ticks, lastTrigger) > WAIT_TICKS_INTERVAL) {
			lastTrigger = ticks;

			// trigger playback

			// NOTE: Due systick arduino 'delay' is not working!

			digitalWrite(DFPLAYER_OUTPUT, LOW);
			delay_ticks(20);
			digitalWrite(DFPLAYER_OUTPUT, HIGH);
			Serial.println("trigger");
		}
	}
	else {
		digitalWrite(ledPin, LOW);
	}
}

int main(void) {

	init();
	setup();

	while (true) {
		loop();
	}
}