From 6708da2661d693f855b6f56d69af1e2fb8502463 Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Tue, 23 Sep 2014 17:24:57 +0200
Subject: Add wakeup source mechanism

Should reduce amount of cpu wakeups with expensive computations.
---
 gyro.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

(limited to 'gyro.c')

diff --git a/gyro.c b/gyro.c
index f31385d..fdf2d1f 100644
--- a/gyro.c
+++ b/gyro.c
@@ -31,7 +31,13 @@ static bool reading = false;
 /* data ready interrupt
  */
 ISR(PCINT0_vect) {
-	/* empty */
+	const bool interrupt = (PINB >> PINB1) & 0x1;
+	/* high-active */
+	if (interrupt) {
+		enableWakeup (WAKE_GYRO);
+	} else {
+		disableWakeup (WAKE_GYRO);
+	}
 }
 
 void gyroInit () {
@@ -60,6 +66,7 @@ void gyroStart () {
 	}
 	sleepwhile (twr.status == TWST_WAIT);
 	puts ("gyroStart done");
+	disableWakeup (WAKE_I2C);
 }
 
 /*	calculate ticks for z rotation
@@ -84,7 +91,9 @@ static void gyroProcessTicks () {
 /*	process gyro sensor data, returns true if new data is available
  */
 bool gyroProcess () {
-	if (reading) {
+	if (reading && shouldWakeup (WAKE_I2C)) {
+		disableWakeup (WAKE_I2C);
+		reading = false;
 		if (twr.status == TWST_OK) {
 			/* new data transfered, process it */
 			/* poor man's noise filter */
@@ -92,19 +101,18 @@ bool gyroProcess () {
 				zaccum += zval;
 			}
 			gyroProcessTicks ();
-			reading = false;
 			return true;
 		} else if (twr.status == TWST_ERR) {
 			puts ("gyro i2c error");
-			reading = false;
 		}
 	} else {
-		if (((PINB >> PINB1) & 0x1) && twr.status == TWST_OK) {
+		if (shouldWakeup (WAKE_GYRO) && twr.status == TWST_OK) {
 			/* new data available in device buffer and bus is free */
 			if (!twRequest (TWM_READ, L3GD20, L3GD20_OUTZ,
 					(uint8_t *) &zval, sizeof (zval))) {
 				puts ("cannot start read");
 			} else {
+				/* wakeup source is disabled by isr to prevent race condition */
 				reading = true;
 			}
 		}
-- 
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