From 6394cc275d247c2761f5aadd57bb9003a4974cd0 Mon Sep 17 00:00:00 2001
From: mikeller <github@ike.ch>
Date: Mon, 20 Aug 2018 15:54:29 +1200
Subject: [PATCH] Fixed problems with accelerometer.

---
 src/main/flight/imu.c           | 10 +++++-----
 src/main/sensors/acceleration.c |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/main/flight/imu.c b/src/main/flight/imu.c
index 8dec160a5..6f6dd85d2 100644
--- a/src/main/flight/imu.c
+++ b/src/main/flight/imu.c
@@ -355,16 +355,16 @@ STATIC_UNIT_TESTED void imuUpdateEulerAngles(void)
 
 static bool imuIsAccelerometerHealthy(float *accAverage)
 {
-    float accMagnitude = 0;
+    float accMagnitudeSq = 0;
     for (int axis = 0; axis < 3; axis++) {
         const float a = accAverage[axis];
-        accMagnitude += a * a;
+        accMagnitudeSq += a * a;
     }
 
-    accMagnitude = sqrtf(accMagnitude) * acc.dev.acc_1G_rec;
+    accMagnitudeSq = accMagnitudeSq * sq(acc.dev.acc_1G_rec);
 
-    // Accept accel readings only in range 0.80g - 1.20g
-    return (0.80f <= accMagnitude) && (accMagnitude <= 1.20f);
+    // Accept accel readings only in range 0.9g - 1.1g
+    return (0.81f < accMagnitudeSq) && (accMagnitudeSq < 1.21f);
 }
 
 // Calculate the dcmKpGain to use. When armed, the gain is imuRuntimeConfig.dcm_kp * 1.0 scaling.
diff --git a/src/main/sensors/acceleration.c b/src/main/sensors/acceleration.c
index e938e1700..882fbccd1 100644
--- a/src/main/sensors/acceleration.c
+++ b/src/main/sensors/acceleration.c
@@ -362,7 +362,7 @@ bool accInit(uint32_t gyroSamplingInverval)
     }
     acc.dev.acc_1G = 256; // set default
     acc.dev.initFn(&acc.dev); // driver initialisation
-    acc.dev.acc_1G_rec = 1 / acc.dev.acc_1G;
+    acc.dev.acc_1G_rec = 1.0f / acc.dev.acc_1G;
     // set the acc sampling interval according to the gyro sampling interval
     switch (gyroSamplingInverval) {  // Switch statement kept in place to change acc sampling interval in the future
     case 500: