1 files changed, 101 insertions, 5 deletions
diff --git a/ardkbd.c b/ardkbd.c
index 2107a5d..1ccb156 100644
--- a/ardkbd.c
+++ b/ardkbd.c
@@ -1,18 +1,114 @@
 #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;
+
+
+#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;
 
-int main() {
-	DDRB  = 0xFF;
+		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:
+			PORTB = 0x20;
+			break;
+
+		case KBD_CODE_DOWN:
+			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) {
-		_delay_ms(1000);
-		PORTB ^= 0x20;
 	}
 
 	return 0;