microcontrolling/main.c

#define __AVR_ATmega2560__
#define F_CPU 16000000UL
#define TICK_BEEP false

#include <avr/io.h>
#include <util/delay.h>
#include <stdbool.h>
#include <avr/interrupt.h>
#include "lib/util.h"
#include "lib/7segment.h"
#include "lib/7segment_4digits.h"

int tick_timer_start =  0xffff - (F_CPU / 1024 / 1000); // 1ms
volatile uint32_t ticks = 0;
volatile beep_time = 0;
volatile bool counting = false;

void start_timer() {
    // Sets the Clock Select. See table on page 157 the Atmel datasheet.
    TCCR1B |= _BV(CS10) | _BV(CS12); // clk/1024
    TCCR2B |= _BV(CS22); // clk/64

    // Set the TOIE (Timer Overflow Interrupt Enable) bit
    // on TIMSK1 (Timer 1 Interrupt Mask Register).
    TIMSK1 |= _BV(TOIE1);
    TIMSK2 |= _BV(TOIE2);

    // Sets the current timer value
    TCNT1 = tick_timer_start;

    // Enable interrupts
    sei();
}

// ISR is used to handle interrupts. TIMER1_OVF_vect
// is triggered whenever timer 1 (16 bit) overflows.
ISR(TIMER1_OVF_vect) {
    TCNT1 = tick_timer_start;
    if (counting) {
        ticks += 1;
        if (TICK_BEEP && ticks % 1000 == 0 && !beep_time) beep_time = 10;
    }

    if (bit_is_set(PIND, PIND0)) {
        PORTD &= 0b11111110;
    } else if (beep_time > 0) {
        PORTD |= 0b00000001;
        beep_time--;
    }
}

ISR(TIMER2_OVF_vect) {
    update_next_digit();
}

void beep() {
    beep_time = 50;
}

void main() {
    DDRF  = 0b11111111;
    DDRK  = 0b00001111;
    DDRD  = 0b00000001;
    PORTK = 0b11000000; // set pull-up

    start_timer();

    float num = 0.0f;
    bool pressed_pause = false;
    bool pressed_clear = false;

    while(1) {
        show_float(ticks / 1000.0f);

        if (!pressed_pause && bit_is_clear(PINK, PINK7)) {
            counting = !counting;
            pressed_pause = true;
            beep();
        } else if (pressed_pause && bit_is_set(PINK, PINK7)) {
            pressed_pause = false;
        }

        if (bit_is_clear(PINK, PINK6)) {
            ticks = 0;
            counting = false;

            if (!pressed_clear) beep();
            pressed_clear = true;
        } else pressed_clear = false;
    }
}