From 2c40f4a0e5c9e9bda8d3b59553abf01abe97c5cd Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Tue, 20 Jan 2015 15:51:50 +0100
Subject: i2c: twRequests returns false if bus is busy

---
 gyro.c | 38 +++++++++++++++++++-------------------
 i2c.c  |  8 ++++++--
 2 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/gyro.c b/gyro.c
index a533e3f..14e25ed 100644
--- a/gyro.c
+++ b/gyro.c
@@ -82,21 +82,21 @@ static void gyroProcessTicks () {
  */
 bool gyroProcess () {
 	switch (state) {
-		case START_REQUEST:
-			if (twr.status == TWST_OK) {
-				/* configuration:
-				 * disable power-down-mode, enable z
-				 * defaults
-				 * high-active, push-pull, drdy on int2
-				 * select 2000dps
-				 */
-				static uint8_t data[] = {0b00001100, 0b0, 0b00001000, 0b00110000};
-				const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
-						sizeof (data)/sizeof (*data));
-				assert (ret);
+		case START_REQUEST: {
+			/* configuration:
+			 * disable power-down-mode, enable z
+			 * defaults
+			 * high-active, push-pull, drdy on int2
+			 * select 2000dps
+			 */
+			static uint8_t data[] = {0b00001100, 0b0, 0b00001000, 0b00110000};
+			const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
+					sizeof (data)/sizeof (*data));
+			if (ret) {
 				state = STARTING;
 			}
 			break;
+		}
 
 		case STARTING:
 			if (shouldWakeup (WAKE_I2C)) {
@@ -105,17 +105,17 @@ bool gyroProcess () {
 			}
 			break;
 
-		case STOP_REQUEST:
-			if (twr.status == TWST_OK) {
-				/* enable power-down mode */
-				static uint8_t data[] = {0b00000000};
+		case STOP_REQUEST: {
+			/* enable power-down mode */
+			static uint8_t data[] = {0b00000000};
 
-				const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
-						sizeof (data)/sizeof (*data));
-				assert (ret);
+			const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
+					sizeof (data)/sizeof (*data));
+			if (ret) {
 				state = STOPPING;
 			}
 			break;
+		}
 
 		case STOPPING:
 			if (shouldWakeup (WAKE_I2C)) {
diff --git a/i2c.c b/i2c.c
index bbee35b..54e1f29 100644
--- a/i2c.c
+++ b/i2c.c
@@ -66,11 +66,15 @@ void twInit () {
 	twr.status = TWST_OK;
 }
 
-/*	high-level write
+/*	high-level write, returns false if bus is busy
  */
 bool twRequest (const twMode mode, const uint8_t address,
 		const uint8_t subaddress, uint8_t * const data, const uint8_t count) {
-	assert (twr.status == TWST_OK);
+	/* busy */
+	if (twr.status != TWST_OK) {
+		return false;
+	}
+
 	assert (count > 0);
 	assert (data != NULL);
 
-- 
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