From 38cbe28e0f229d39fd2c9892a3ecbfded3c2a8bc Mon Sep 17 00:00:00 2001
From: Dominic Clifton <me@dominicclifton.name>
Date: Fri, 1 Aug 2014 21:10:26 +0100
Subject: [PATCH] Apply accz pt1 element fixes.

See:
f7132b9d33211a55b8bd2c92f14da59f35b715a4
b1f58bc01fcf1632b3c3947a5ed0e807c2763a30
5832e2f67fcd2ee93044b300fda37a420c595813
a5961aeda657225fa843a115a94229313db4b2db
---
 src/main/flight/imu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/main/flight/imu.c b/src/main/flight/imu.c
index 3c8671fc18..20ea3250f5 100755
--- a/src/main/flight/imu.c
+++ b/src/main/flight/imu.c
@@ -214,10 +214,14 @@ static const float fc_acc = 0.5f / (M_PI * F_CUT_ACCZ);
 void acc_calc(uint32_t deltaT)
 {
     static int32_t accZoffset = 0;
-    static float accz_smooth;
+    static float accz_smooth = 0;
+    float dT;
     fp_angles_t rpy;
     t_fp_vector accel_ned;
 
+    // deltaT is measured in us ticks
+    dT = (float)deltaT * 1e-6f;
+
     // the accel values have to be rotated into the earth frame
     rpy.angles.roll = -(float)anglerad[AI_ROLL];
     rpy.angles.pitch = -(float)anglerad[AI_PITCH];
@@ -238,7 +242,7 @@ void acc_calc(uint32_t deltaT)
     } else
         accel_ned.V.Z -= acc_1G;
 
-    accz_smooth = accz_smooth + (deltaT / (fc_acc + deltaT)) * (accel_ned.V.Z - accz_smooth); // low pass filter
+    accz_smooth = accz_smooth + (dT / (fc_acc + dT)) * (accel_ned.V.Z - accz_smooth); // low pass filter
 
     // apply Deadband to reduce integration drift and vibration influence
     accSum[X] += applyDeadband(lrintf(accel_ned.V.X), accDeadband->xy);