From 85ec57bb6f545084426527ecc80269544b904067 Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Wed, 26 Feb 2014 11:49:34 +0100
Subject: Add gyroscope abstraction layer

---
 gyroscope.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 gyroscope.c

(limited to 'gyroscope.c')

diff --git a/gyroscope.c b/gyroscope.c
new file mode 100644
index 0000000..0f932c2
--- /dev/null
+++ b/gyroscope.c
@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/sleep.h>
+
+#include "i2c.h"
+#include "gyroscope.h"
+
+/* device address */
+#define L3GD20 0b11010100
+/* registers */
+#define L3GD20_WHOAMI 0xf
+#define L3GD20_CTRLREG1 0x20
+#define L3GD20_CTRLREG3 0x22
+#define L3GD20_CTRLREG4 0x23
+
+#define sleepwhile(cond) \
+	sleep_enable (); \
+	while (cond) { sleep_cpu (); } \
+	sleep_disable ();
+
+/* the first interrupt is lost */
+volatile bool drdy = true;
+volatile int16_t val[3] = {0, 0, 0};
+
+/* data ready interrupt
+ */
+ISR(PCINT0_vect) {
+	drdy = true;
+}
+
+void gyroscopeInit () {
+	/* set PB1 to input, with pull-up */
+	DDRB = (DDRB & ~((1 << PB1)));
+	PORTB = (PORTB | (1 << PB1));
+	/* enable interrupt PCI0 */
+	PCICR = (1 << PCIE0);
+	/* enable interrupts on PB1/PCINT1 */
+	PCMSK0 = (1 << 1);
+}
+
+/* XXX: make nonblocking */
+void gyroscopeStart () {
+	/* XXX: implement multi-write */
+	/* disable power-down-mode */
+	if (!twWrite (L3GD20, L3GD20_CTRLREG1, 0b00001111)) {
+		printf ("cannot start write\n");
+	}
+	sleepwhile (twr.status == TWST_WAIT);
+	printf ("final twi status was %i\n", twr.status);
+
+	/* enable drdy interrupt */
+	if (!twWrite (L3GD20, L3GD20_CTRLREG3, 0b00001000)) {
+		printf ("cannot start write\n");
+	}
+	sleepwhile (twr.status == TWST_WAIT);
+	printf ("final twi status was %i\n", twr.status);
+
+	/* select 500dps */
+	if (!twWrite (L3GD20, L3GD20_CTRLREG4, 0b00010000)) {
+		printf ("cannot start write\n");
+	}
+	sleepwhile (twr.status == TWST_WAIT);
+	printf ("final twi status was %i\n", twr.status);
+}
+
+bool gyroscopeRead () {
+	if (drdy) {
+		drdy = false;
+
+		if (!twReadMulti (L3GD20, 0x28, (uint8_t *) val, 6)) {
+			printf ("cannot start read\n");
+		}
+
+		return true;
+	} else {
+		return false;
+	}
+}
+
+volatile const int16_t *gyroscopeGet () {
+	return val;
+}
+
-- 
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