kbd.c


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#include "kbd.h"

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#include <stdbool.h>
#include <stdint.h>


static volatile int8_t kbd_state = 0;

static volatile uint8_t kbd_input = 0;
static volatile uint8_t kbd_output = 0;
static volatile uint8_t kbd_flags = 0;


static volatile uint8_t ts = 10;


static inline bool kbd_data() {
	return (PINC & (1 << 0));
}

static inline bool kbd_clock() {
	return (PINC & (1 << 1));
}


static inline void kbd_clock_down() {
	DDRC |= 0x02;
	PORTC &= ~0x02;
}

static inline void kbd_clock_in() {
	DDRC &= ~0x02;
	PORTC |= 0x02;
}

static inline void kbd_data_set(bool state) {
	if (state)
		PORTC |= 0x01;
	else
		PORTC &= ~0x01;
}

static inline void kbd_data_out() {
	DDRC |= 0x01;
}

static inline void kbd_data_in() {
	DDRC &= ~0x01;
	PORTC |= 0x01;
}


static inline void kbd_wait() {
	while (kbd_state) {}
}


ISR(PCINT1_vect) {
	if (kbd_clock())
		return;

	if (kbd_state < 0) {
		if (kbd_state >= -8) {
			kbd_data_set(kbd_output & _BV(-1-kbd_state));
		}
		else if (kbd_state == -9) {
			kbd_data_set(!(__builtin_popcount(kbd_output) & 1));
		}
		else if (kbd_state == -10) {
			kbd_data_in();
		}
		else {
			kbd_state = 0;
			return;
		}

		kbd_state--;
		return;
	}

	bool data = kbd_data();

	if (kbd_state == 0) {
		if (!data) { /* start bit */
			kbd_input = 0;
			kbd_state++;
		}

		return;
	}

	if (kbd_state <= 8) {
		if (data)
			kbd_input |= _BV(kbd_state-1);
		kbd_state++;
		return;
	}

	if (kbd_state == 9) {
		if ((__builtin_popcount(kbd_input) & 1) == data)
			kbd_flags |= KBD_FLAG_ERROR;

		kbd_state++;
		return;
	}

	kbd_state = 0;

	if (kbd_flags & KBD_FLAG_ERROR) {
		/* Retry */
		return;
	}

	if (kbd_input == 0xe0) {
		kbd_flags |= KBD_FLAG_EXT;
		return;
	}

	if (kbd_input == 0xf0) {
		kbd_flags |= KBD_FLAG_BREAK;
		return;
	}

	uint16_t code = kbd_input;
	if (kbd_flags & KBD_FLAG_EXT)
		code |= 0xe000;

	kbd_handle(code, !(kbd_flags & KBD_FLAG_BREAK));

	kbd_flags = 0;
}


void kbd_send(uint8_t command) {
	kbd_wait();

	kbd_clock_down();
	_delay_us(100);

	kbd_data_out();
	kbd_data_set(false);
	_delay_us(10);

	kbd_clock_in();

	kbd_output = command;
	kbd_state = -1;

	kbd_wait();

	/* wait for ack */
	while (!kbd_state) {}

	kbd_wait();
}

void kbd_init(void) {
	DDRC  &= ~0x03;
	PORTC |= 0x03;

	PCMSK1 = (1 << PCINT9);
	PCICR = (1 << PCIE1);
}