digital_clock.c

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/******************************************************************************
 @copyright Copyright © 2022 by Jason Duffy
 
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/**
 * @file digital_clock.c
 * @ingroup digital_clock
 * @author Jason Duffy
 * @date 2nd April 2022
 * @brief Driver to provide setup and configuration of the timer/counter
 * hardware on the ATmega328P.
 * @details
 * @bug No known bugs. 
 * @see
 */
 
#include <avr/interrupt.h>
 
#include "digital_clock.h"
 
#define PRESCALER           64
#define UNITS_PER_SECOND    1000
 
/**
 * File scope variables for digital clock functionality.
 * Must be declared volatile if used in ISR. 
 */
static volatile uint16_t milliseconds = 0;
static volatile uint8_t seconds = 0;
static volatile uint8_t minutes = 31;
static volatile uint8_t hours = 22;
 
static char msg[9] = {0};
 
 
/**
 * Interrupt Service Routine. 
 */
ISR(TIMER0_COMPA_vect)
{
    if (milliseconds < 999)
    {
        ++milliseconds;
    }
    else
    {
        milliseconds = 0;
 
        if (seconds < 59)
        {
            ++seconds;
        }
        else
        {
            seconds = 0;
 
            if (minutes < 59)
            {
                ++minutes;
            }
            else
            {
                minutes = 0;
 
                if (hours < 23)
                {
                    ++hours;
                }
                else
                {
                    hours = 0;
                }
            }
        }
    }
}
 
/*
 * Initialisation routine for 8-bit timer 0.
 */
void init_timer_counter_0(void)
{
    /*
    cli();
    OCR0A = 125; // Set initial compare value A.
 
    TCCR0A |= (1 << WGM01); // CTC mode, OCR0A is TOP
    TCCR0B |= (1 << CS00) | (1 << CS01); // start timer with 64 prescaler
    TIMSK0 |= (1 << OCIE0A); // enable output compare interrupt for OCR4A
    sei();
    */
 
    cli();
    OCR0A = (F_CPU / PRESCALER / UNITS_PER_SECOND);
    TCCR0A |= (1 << WGM01); // CTC mode, OCR0A is TOP
    TCCR0B |= (1 << CS00) | (1 << CS01); // start timer with 64 prescaler
    TIMSK0 |= (1 << OCIE0A); // enable output compare interrupt for OCR4A
    sei();
 
}
 
 
/*
 * Setter function for time variables. 
 */
void set_time(uint8_t hrs, uint8_t mins, uint8_t secs)
{
    cli();
    hours = hrs;
    minutes = mins;
    seconds = secs;
    sei();
}
 
 
/*
 * Getter function for time variables.
 * Returns current time as a string eg. 22:03:11
 */
char* get_time(void)
{
    // Store hours as a string.
    msg[0] = '0' + (hours / 10); // 10's
    msg[1] = '0' + (hours % 10); // 1's 
 
    msg[2] = ':';
 
    // Store minutes as a string.
    msg[3] = '0' + (minutes / 10); // 10's
    msg[4] = '0' + (minutes % 10); // 1's
 
    msg[5] = ':';
 
    // Store seconds as a string.
    msg[6] = '0' + (seconds / 10); // 10's
    msg[7] = '0' + (seconds % 10); // 1's
 
    return msg;
}
 
 
/*** end of file ***/