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-rw-r--r--gyroscope.c84
1 files changed, 84 insertions, 0 deletions
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;
+}
+