[sensors][win] Reverse axis signs for motion sensors

This CL reverses axis signs for gyroscope, magnetometer and absolute
orientation sensors. Before the change, wrong coordinate system was
used based on the accelerometer's data. Integrating Motion and Orientation
Sensors [1] document, explains what coordinate system must be used and why
accelerometer's measurements differ from other platforms.

[1] https://msdn.microsoft.com/en-us/library/windows/hardware/dn642102(v=vs.85).aspx

Bug: 786252
Change-Id: I4afbc1a1d5fb03c3e2e0538a8ea7424c40020eca
Reviewed-on: https://chromium-review.googlesource.com/804624Reviewed-by: Mikhail Pozdnyakov <mikhail.pozdnyakov@intel.com>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Jun Cai <juncai@chromium.org>
Commit-Queue: Alexander Shalamov <alexander.shalamov@intel.com>
Cr-Commit-Position: refs/heads/master@{#522380}

services/device/generic_sensor/platform_sensor_and_provider_unittest_win.cc

@@ -599,9 +599,9 @@ TEST_F(PlatformSensorAndProviderTestWin, CheckGyroscopeReadingConversion) {
   base::RunLoop().RunUntilIdle();
   SensorReadingSharedBuffer* buffer =
       static_cast<SensorReadingSharedBuffer*>(mapping.get());
-  EXPECT_THAT(buffer->reading.gyro.x, gfx::DegToRad(-x_ang_accel));
-  EXPECT_THAT(buffer->reading.gyro.y, gfx::DegToRad(-y_ang_accel));
-  EXPECT_THAT(buffer->reading.gyro.z, gfx::DegToRad(-z_ang_accel));
+  EXPECT_THAT(buffer->reading.gyro.x, gfx::DegToRad(x_ang_accel));
+  EXPECT_THAT(buffer->reading.gyro.y, gfx::DegToRad(y_ang_accel));
+  EXPECT_THAT(buffer->reading.gyro.z, gfx::DegToRad(z_ang_accel));
   EXPECT_TRUE(sensor->StopListening(client.get(), configuration));
 }
 
@@ -639,9 +639,9 @@ TEST_F(PlatformSensorAndProviderTestWin, CheckMagnetometerReadingConversion) {
   base::RunLoop().RunUntilIdle();
   SensorReadingSharedBuffer* buffer =
       static_cast<SensorReadingSharedBuffer*>(mapping.get());
-  EXPECT_THAT(buffer->reading.magn.x, -x_magn_field * kMicroteslaInMilligauss);
-  EXPECT_THAT(buffer->reading.magn.y, -y_magn_field * kMicroteslaInMilligauss);
-  EXPECT_THAT(buffer->reading.magn.z, -z_magn_field * kMicroteslaInMilligauss);
+  EXPECT_THAT(buffer->reading.magn.x, x_magn_field * kMicroteslaInMilligauss);
+  EXPECT_THAT(buffer->reading.magn.y, y_magn_field * kMicroteslaInMilligauss);
+  EXPECT_THAT(buffer->reading.magn.z, z_magn_field * kMicroteslaInMilligauss);
   EXPECT_TRUE(sensor->StopListening(client.get(), configuration));
 }
 
@@ -730,9 +730,9 @@ TEST_F(PlatformSensorAndProviderTestWin,
   SensorReadingSharedBuffer* buffer =
       static_cast<SensorReadingSharedBuffer*>(mapping.get());
 
-  EXPECT_THAT(buffer->reading.orientation_quat.x, -x);
-  EXPECT_THAT(buffer->reading.orientation_quat.y, -y);
-  EXPECT_THAT(buffer->reading.orientation_quat.z, -z);
+  EXPECT_THAT(buffer->reading.orientation_quat.x, x);
+  EXPECT_THAT(buffer->reading.orientation_quat.y, y);
+  EXPECT_THAT(buffer->reading.orientation_quat.z, z);
   EXPECT_THAT(buffer->reading.orientation_quat.w, w);
   EXPECT_TRUE(sensor->StopListening(client.get(), configuration));
 }

services/device/generic_sensor/platform_sensor_reader_win.cc

@@ -88,9 +88,15 @@ std::unique_ptr<ReaderInitParams> CreateAccelerometerReaderInitParams() {
       return E_FAIL;
     }
 
-    // Windows uses coordinate system where Z axis points down from device
-    // screen, therefore, using right hand notation, we have to reverse
-    // sign for each axis. Values are converted from G/s^2 to m/s^2.
+    // Windows HW sensor integration requirements specify accelerometer
+    // measurements conventions such as, the accelerometer sensor must expose
+    // values that are proportional and in the same direction as the force of
+    // gravity. Therefore, sensor hosted by the device at rest on a leveled
+    // surface while the screen is facing towards the sky, must report -1G along
+    // the Z axis.
+    // https://msdn.microsoft.com/en-us/library/windows/hardware/dn642102(v=vs.85).aspx
+    // Change sign of values, to report 'reaction force', and convert values
+    // from G/s^2 to m/s^2 units.
     reading->accel.x = -x * kMeanGravity;
     reading->accel.y = -y * kMeanGravity;
     reading->accel.z = -z * kMeanGravity;
@@ -119,12 +125,10 @@ std::unique_ptr<ReaderInitParams> CreateGyroscopeReaderInitParams() {
       return E_FAIL;
     }
 
-    // Windows uses coordinate system where Z axis points down from device
-    // screen, therefore, using right hand notation, we have to reverse
-    // sign for each axis. Values are converted from deg to rad.
-    reading->gyro.x = gfx::DegToRad(-x);
-    reading->gyro.y = gfx::DegToRad(-y);
-    reading->gyro.z = gfx::DegToRad(-z);
+    // Values are converted from degrees to radians.
+    reading->gyro.x = gfx::DegToRad(x);
+    reading->gyro.y = gfx::DegToRad(y);
+    reading->gyro.z = gfx::DegToRad(z);
     return S_OK;
   };
   return params;
@@ -150,13 +154,10 @@ std::unique_ptr<ReaderInitParams> CreateMagnetometerReaderInitParams() {
       return E_FAIL;
     }
 
-    // Windows uses coordinate system where Z axis points down from device
-    // screen, therefore, using right hand notation, we have to reverse
-    // sign for each axis. Values are converted from Milligaus to
-    // Microtesla.
-    reading->magn.x = -x * kMicroteslaInMilligauss;
-    reading->magn.y = -y * kMicroteslaInMilligauss;
-    reading->magn.z = -z * kMicroteslaInMilligauss;
+    // Values are converted from Milligaus to Microtesla.
+    reading->magn.x = x * kMicroteslaInMilligauss;
+    reading->magn.y = y * kMicroteslaInMilligauss;
+    reading->magn.z = z * kMicroteslaInMilligauss;
     return S_OK;
   };
   return params;
@@ -204,12 +205,9 @@ CreateAbsoluteOrientationQuaternionReaderInitParams() {
 
     float* quat = reinterpret_cast<float*>(quat_variant.get().caub.pElems);
 
-    // Windows uses coordinate system where Z axis points down from device
-    // screen, therefore, using right hand notation, we have to reverse
-    // sign for each quaternion component.
-    reading->orientation_quat.x = -quat[0];  // x*sin(Theta/2)
-    reading->orientation_quat.y = -quat[1];  // y*sin(Theta/2)
-    reading->orientation_quat.z = -quat[2];  // z*sin(Theta/2)
+    reading->orientation_quat.x = quat[0];  // x*sin(Theta/2)
+    reading->orientation_quat.y = quat[1];  // y*sin(Theta/2)
+    reading->orientation_quat.z = quat[2];  // z*sin(Theta/2)
     reading->orientation_quat.w = quat[3];  // cos(Theta/2)
     return S_OK;
   };