digital_clock.c File Reference

Driver to provide setup and configuration of the timer/counter hardware on the ATmega328P. More...

#include <avr/interrupt.h>
#include "digital_clock.h"

Go to the source code of this file.

Macros
#define	PRESCALER   64
#define	UNITS_PER_SECOND   1000

Functions
	ISR (TIMER0_COMPA_vect)
	Interrupt Service Routine. More...
void	init_timer_counter_0 (void)
	Initialisation routine for 8-bit timer 0. More...
void	set_time (uint8_t hrs, uint8_t mins, uint8_t secs)
	Setter function for time variables. More...
char *	get_time (void)
	Getter function for time variables. More...

Detailed Description

Driver to provide setup and configuration of the timer/counter hardware on the ATmega328P.

Copyright

Copyright © 2022 by Jason Duffy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Author

Jason Duffy

Date

2nd April 2022

See also

Definition in file digital_clock.c.

Macro Definition Documentation

PRESCALER

#define PRESCALER   64

Definition at line 39 of file digital_clock.c.

UNITS_PER_SECOND

#define UNITS_PER_SECOND   1000

Definition at line 40 of file digital_clock.c.

Function Documentation

ISR()

ISR

(

TIMER0_COMPA_vect

)

Interrupt Service Routine.

Definition at line 57 of file digital_clock.c.

{
    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;
                }
            }
        }
    }
}

init_timer_counter_0()

void init_timer_counter_0

(

void

)

Initialisation routine for 8-bit timer 0.

Definition at line 99 of file digital_clock.c.

{
    /*
    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();
 
}

set_time()

void set_time	(	uint8_t	hrs,
		uint8_t	mins,
		uint8_t	secs
	)

Setter function for time variables.

Definition at line 124 of file digital_clock.c.

{
    cli();
    hours = hrs;
    minutes = mins;
    seconds = secs;
    sei();
}

get_time()

char * get_time

(

void

)

Getter function for time variables.

Returns current time as a string eg. 22:03:11

Definition at line 138 of file digital_clock.c.

{
    // 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;
}