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#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdbool.h>
#include <stdint.h>
static volatile uint8_t kbd_state = 0;
static volatile uint8_t kbd_input = 0;
static volatile uint8_t kbd_flags = 0;
static volatile uint8_t ts = 10;
#define KBD_FLAG_ERROR (_BV(0))
#define KBD_FLAG_BREAK (_BV(1))
#define KBD_FLAG_EXT (_BV(2))
#define KBD_CODE_UP 0xe075
#define KBD_CODE_LEFT 0xe06b
#define KBD_CODE_DOWN 0xe072
#define KBD_CODE_RIGHT 0xe074
static inline bool kbd_data() {
return (PINC & (1 << 0));
}
static inline bool kbd_clock() {
return (PINC & (1 << 1));
}
ISR(PCINT1_vect) {
if (kbd_clock())
return;
bool data = kbd_data();
if (kbd_state == 0) {
if (!data) { /* start bit */
kbd_input = 0;
kbd_state++;
}
return;
}
if (kbd_state <= 8) {
kbd_input |= (data << (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;
if (!(kbd_flags & KBD_FLAG_BREAK)) {
switch (code) {
case KBD_CODE_UP:
if (ts > 0)
ts--;
break;
case KBD_CODE_DOWN:
if (ts < 31)
ts++;
PORTB = 0;
break;
}
}
kbd_flags = 0;
}
int main(void) {
DDRB = 0xff;
PORTB = 0;
DDRC = 0x00;
PORTC = 0x03;
PCMSK1 = (1 << PCINT9);
PCICR = (1 << PCIE1);
sei();
while(true) {
PORTB ^= 0x20;
uint32_t i;
for (i = 0; i < (1 << ts); i++)
_delay_ms(1);
}
return 0;
}
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