1 files changed, 216 insertions, 0 deletions
diff --git a/kbd.c b/kbd.c
new file mode 100644
index 0000000..02c23a5
--- /dev/null
+++ b/kbd.c
@@ -0,0 +1,216 @@
+#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;
+
+
+#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));
+}
+
+
+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;
+
+	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++;
+			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();
+}
+
+
+int main(void) {
+	DDRB  = 0xff;
+	PORTB = 0;
+
+	DDRC  = 0x00;
+	PORTC = 0x03;
+
+	PCMSK1 = (1 << PCINT9);
+	PCICR = (1 << PCIE1);
+
+	sei();
+
+	kbd_send(0xff);
+
+	uint8_t l = 0;
+
+	while(true) {
+		uint8_t state = PORTB ^ 0x20;
+		PORTB = state;
+
+		if (state & 0x20) {
+			l = (l+1)%3;
+
+			kbd_send(0xed);
+			kbd_send(1 << l);
+		}
+
+		uint32_t i;
+		for (i = 0; i < (1 << ts); i++)
+			_delay_ms(1);
+	}
+
+	return 0;
+}