120 lines
3.4 KiB
C
120 lines
3.4 KiB
C
/*
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* Button with debouncing. Based on Lab Book Pages pseudocode.
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*
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* http://www.labbookpages.co.uk/electronics/debounce.html
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* http://www.arduino.cc/en/Tutorial/Debounce
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*
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* To compile and upload run: make clean; make; make program;
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*
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* Copyright 2011 Mika Tuupola
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*
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* Licensed under the MIT license:
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* http://www.opensource.org/licenses/mit-license.php
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*
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*/
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#ifndef F_CPU
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#define F_CPU 16000000UL
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#endif
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#include <stdlib.h>
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#include <avr/io.h>
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#include <stdio.h>
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#include <util/delay.h>
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#include <stdint.h>
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#include <avr/sfr_defs.h>
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#include "main.h"
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#include "uart.h"
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#include "timer.h"
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void init(void) {
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/* Make PORTD2 (Arduino digital 2) input by clearing bit in DDR */
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DDRD &= ~(_BV(PORTD2));
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/* In input mode, when pull-up is enabled, default state of pin becomes ’1′. So even if */
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/* you don’t connect anything to pin and if you try to read it, it will read as 1. Now, */
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/* when you externally drive that pin to zero(i.e. connect to ground / or pull-down), */
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/* only then it will be read as 0. */
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/* Enable pullups by setting bits in PORT. Default state is now high. */
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PORTD |= (_BV(PORTD2));
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/* Make PORTB5 (Arduino digital 13) an output by setting bit in DDR. */
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DDRB |= _BV(PORTB5);
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}
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uint8_t digital_read(int input_register, int pin) {
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return bit_is_set(input_register, pin) != 0 ? 1 : 0;
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}
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/* You could use cbi ie &= ~ or sbi ie |= but this makes code more readable. */
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void digital_write(volatile uint8_t *data_port, uint8_t pin, uint8_t value) {
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if (0 == value) {
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*data_port &= ~(_BV(pin));
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} else {
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*data_port |= _BV(pin);
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}
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}
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int main(void) {
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init();
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timer_init();
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uart_init();
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stdout = &uart_output;
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stdin = &uart_input;
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uint8_t current_reading;
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uint8_t current_state = 0;
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uint8_t shift_register = 0;
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/* Rest of the variables are used only for debugging output. */
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uint8_t previous_reading = 0;
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uint8_t previous_state = 0;
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uint64_t last_toggle_time;
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while (1) {
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/* Shift the register towards the most significant bit. */
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shift_register = shift_register << 1;
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current_reading = digital_read(PIND, PIND2);
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/* Set least significant bit to current reading. */
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if (1 == current_reading) {
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shift_register |= _BV(0);
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} else {
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shift_register &= ~(_BV(0));
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}
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/* Used only for debugging purposes. */
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if (current_reading != previous_reading) {
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/* Note the time in millis of last change of button state. */
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last_toggle_time = timer_millis();
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printf("- Reading toggled %d (%d)\n", current_reading, last_toggle_time);
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}
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/* If shift register is 0b00000000 or 0b11111111 switch has been */
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/* high or low long enough to assume reading is not noise. */
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if (0 == shift_register) {
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current_state = 0;
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} else if (255 == shift_register){
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current_state = 1;
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}
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/* Used only for debugging purposes. */
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if (current_state != previous_state) {
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printf("+ State toggled %d (%d)\n", current_state, last_toggle_time);
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previous_state = current_state;
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}
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previous_reading = current_reading;
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}
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return 0;
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}
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