matemat/main.c

#include <stdlib.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>

#include "lcd_routines.h"
#include "uart.h"

#define SAVE		PD2
#define SIGNAL		PD3
#define FREQ_DOWN	PD4
#define FREQ_UP		PD5
#define AMP_DOWN	PD6
#define AMP_UP		PD7
#define KEY_DDR		DDRD
#define KEY_PORT	PORTD
#define KEY_PIN		PIND

#define LED_PIN		PA7
#define LED_PORT	PORTA
#define LED_DDR		DDRA

#define led_on()	LED_PORT |= _BV(LED_PORT);
#define led_off()	LED_PORT &= ~_BV(LED_PORT);

#define UART_BAUD_RATE      9600

#define ALL_KEYS	(_BV(SAVE) | _BV(SIGNAL) | _BV(FREQ_DOWN) | _BV(FREQ_UP) | _BV(AMP_DOWN) | _BV(AMP_UP) )

#define REPEAT_MASK     ALL_KEYS
#define REPEAT_START    50
#define REPEAT_NEXT     20

volatile uint8_t key_state; // debounced and inverted key state:
// bit = 1: key pressed
volatile uint8_t key_press; // key press detect

volatile uint8_t key_rpt; // key long press and repeat

/* prototypes */
void init_io();
uint8_t get_key_press(uint8_t key_mask);

int main(void) {
	init_io();
	lcd_init();
	uart_init(UART_BAUD_SELECT(UART_BAUD_RATE,F_CPU));

	lcd_setcursor(0, 0);

	unsigned int c;

	sei();

	for (;;) {
		if (uart_available() > 0) {
			c = uart_getc();

			if (c == '*') {
				lcd_clear();
			} else if (c == '+') {
				lcd_setcursor(0, 2);
			} else {
				lcd_data(c);
			}
		}

		if (get_key_press(_BV(FREQ_DOWN))) {
			uart_putc('f');
		}
		if (get_key_press(_BV(FREQ_UP))) {
			uart_putc('F');
		}
		if (get_key_press(_BV(SIGNAL))) {
			uart_putc('s');
		}
		if (get_key_press(_BV(AMP_UP))) {
			uart_putc('A');
		}
		if (get_key_press(_BV(AMP_DOWN))) {
			uart_putc('a');
		}
		if (get_key_press(_BV(SAVE))) {
			uart_putc('v');
		}

	}

}

void init_io() {
	KEY_DDR &= ~ALL_KEYS; // configure key port for input
	KEY_PORT |= ALL_KEYS;
	LED_DDR |= _BV(LED_PIN);

	TCCR0 = (1 << CS02) | (1 << CS00); // divide by 1024
	TCNT0 = (uint8_t) (int16_t) -(F_CPU / 1024 * 10e-3 + 0.5); // preload for 10ms
	TIMSK |= 1 << TOIE0; // enable timer interrupt
}

ISR( TIMER0_OVF_vect ) {
	static uint8_t ct0, ct1, rpt;
	uint8_t i;

	TCNT0 = (uint8_t) (int16_t) -(F_CPU / 1024 * 10e-3 + 0.5); // preload for 10ms

	i = key_state ^ ~KEY_PIN; // key changed ?
	ct0 = ~(ct0 & i); // reset or count ct0
	ct1 = ct0 ^ (ct1 & i); // reset or count ct1
	i &= ct0 & ct1; // count until roll over ?
	key_state ^= i; // then toggle debounced state
	key_press |= key_state & i; // 0->1: key press detect

	if ((key_state & REPEAT_MASK) == 0) // check repeat function
		rpt = REPEAT_START; // start delay
	if (--rpt == 0) {
		rpt = REPEAT_NEXT; // repeat delay
		key_rpt |= key_state & REPEAT_MASK;
	}
}

uint8_t get_key_press(uint8_t key_mask) {
	cli();
	// read and clear atomic !
	key_mask &= key_press; // read key(s)
	key_press ^= key_mask; // clear key(s)
	sei();
	return key_mask;
}