From 9054f9a5267bee98cdf73bfd4ef368e3512f0491 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Tue, 11 Dec 2012 23:06:23 +0100
Subject: Snake

---
 kbd.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 kbd.c

(limited to 'kbd.c')

diff --git a/kbd.c b/kbd.c
new file mode 100644
index 0000000..e3342e9
--- /dev/null
+++ b/kbd.c
@@ -0,0 +1,167 @@
+#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);
+}
-- 
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