To use:

• define include path to appriopriate port file “button_port.h”
• define include path to appriopriate config file “button_config.h”
• define global (or local) variable of Button type and export variable to every file timer is in use (if applicable).
• include button.h file in every file timer is in use.
• invoke Button_service in fixed intervals. If called from within interrupt service routine be aware that callbacks’ll be runnging in interrupt context.

Usage example

ATmega328p

/* main.c */
#include <avr/io.h>
#include <avr/interrupt.h>
#include "timer.h"
#include "software_timer.h"
#include "button.h"
#define BUTTON_PERIOD_MS 20
#define LED_BLINK 250
Timer buttonPoll;
Timer ledBlink;
Button btns;
void press(ButtonPort mask);
void release(ButtonPort mask);
void led_init(void);
void led_toggle(void);
void led_off(void);
int main() __attribute__((OS_main));
int main()
{
    timer_init();
    led_init();
    Timer_ctor(&buttonPoll);
    Timer_setPeriod(&buttonPoll, TICKS(BUTTON_PERIOD_MS,HARDWARE_TICK_MS));
    Timer_ctor(&ledBlink);
    Timer_setPeriod(&ledBlink, TICKS(LED_BLINK, HARDWARE_TICK_MS));
    /* pull ups on inputs */
    Button_initInputs();
    /* Button class constructor */
    Button_ctor(&btns,press,release);
    sei();
    while(1)
    {
        /* called every BUTTON_PERIOD_MS milliseconds */
        if(Timer_isTime(&buttonPoll)) {
            Button_service(&btns);
            Timer_setPeriod(&buttonPoll, TICKS(BUTTON_PERIOD_MS,HARDWARE_TICK_MS));
        }
        if(Timer_isTime(&ledBlink)) {
            led_toggle();
            Timer_setPeriod(&ledBlink, TICKS(LED_BLINK, HARDWARE_TICK_MS));
        }
    }
}
void press(ButtonPort mask)
{
    /* use mask parameter to identify which button was just pressed */
    Timer_activate(&ledBlink,0);
    led_off();
}
void release(ButtonPort mask)
{
    /* if needed use mask parameter to identify which button was just released */
    Timer_activate(&ledBlink,1);
}
void led_init(void)
{
    DDRB = _BV(5);
}
void led_toggle(void)
{
    PINB = _BV(5);
}
void led_off(void)
{
    PORTB &= ~_BV(5);
}
/* timer.h */
#define HARDWARE_TICK_MS 4
/* timer.c */
#include <avr/io.h>
#include <avr/interrupt.h>
#include "software_timer.h"
Timer buttonPoll;
Timer ledBlink;
void timer_init(void)
{
    TIMSK0 = _BV(TOIE0);
    TCCR0B = _BV(CS02);
}
ISR(TIMER0_OVF_vect)
{
    Timer_count(&buttonPoll);
    Timer_count(&ledBlink);
}