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avr_demo/button_debounce_timer/main.c
2011-10-12 00:04:57 +03:00

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/*
* Button with debouncing. Based on the Arduino example but without
* Arduino libraries.
*
* http://www.arduino.cc/en/Tutorial/Debounce
*
* To compile and upload run: make clean; make; make program;
*
* Copyright 2011 Mika Tuupola
*
* Licensed under the MIT license:
* http://www.opensource.org/licenses/mit-license.php
*
*/
#ifndef F_CPU
#define F_CPU 16000000UL
#endif
#include <stdlib.h>
#include <avr/io.h>
#include <stdio.h>
#include <util/delay.h>
#include <stdint.h>
#include <avr/sfr_defs.h>
#include "main.h"
#include "uart.h"
#include "timer.h"
void init(void) {
/* Make PORTD2 (Arduino digital 2) input by clearing bit in DDR */
DDRD &= ~(_BV(PORTD2));
/* In input mode, when pull-up is enabled, default state of pin becomes 1. So even if */
/* you dont connect anything to pin and if you try to read it, it will read as 1. Now, */
/* when you externally drive that pin to zero(i.e. connect to ground / or pull-down), */
/* only then it will be read as 0. */
/* Enable pullups by setting bits in PORT. Default state is now high. */
PORTD |= (_BV(PORTD2));
/* Make PORTB5 (Arduino digital 13) an output by setting bit in DDR. */
DDRB |= _BV(PORTB5);
}
uint8_t digital_read(int input_register, int pin) {
return bit_is_set(input_register, pin) != 0 ? 1 : 0;
}
/* You could use cbi ie &= ~ or sbi ie |= but this makes code more readable. */
void digital_write(volatile uint8_t *data_port, uint8_t pin, uint8_t value) {
if (0 == value) {
*data_port &= ~(_BV(pin));
} else {
*data_port |= _BV(pin);
}
}
int main(void) {
init();
timer_init();
uart_init();
stdout = &uart_output;
stdin = &uart_input;
uint8_t current_reading;
uint8_t previous_reading = 0;
uint8_t current_state = 0;
uint8_t previous_state = 0;
uint64_t last_toggle_time;
while (1) {
current_reading = digital_read(PIND, PIND2);
if (current_reading != previous_reading) {
/* Note the time in millis of last change of button state. */
last_toggle_time = timer_millis();
printf("- Reading toggled %d (%d)\n", current_reading, last_toggle_time);
}
/* If there has been more than 10 millis since last toggling */
/* of button state, assume it is real and not bouncing noise. */
if ((timer_millis() - last_toggle_time) > 10) {
current_state = current_reading;
}
/* Just for debugging purposes. */
if (current_state != previous_state) {
printf("+ State toggled %d (%d)\n", current_state, last_toggle_time);
previous_state = current_state;
}
previous_reading = current_reading;
}
return 0;
}