sensors: correctly scale the accelerometer values

The UPM accelerometers' values are in counts/g. However, the sensors.h
mandates that the values should be in SI units (m/s^2).
Scale the values by multiplying with the gravitational acceleration
constant.

BUG=26009894

Tracked-On: https://jira01.devtools.intel.com/browse/BP-145
Change-Id: If9d4733fd2f70c4c4faebdcd39804f7463fc3eef
Signed-off-by: Constantin Musca <constantin.musca@intel.com>

4 files changed, 13 insertions, 0 deletions

diff --git a/peripheral/sensors/edison_arduino/Sensor.cpp b/peripheral/sensors/edison_arduino/Sensor.cpp
index e44ff60..8a93b81 100644
--- a/peripheral/sensors/edison_arduino/Sensor.cpp
+++ b/peripheral/sensors/edison_arduino/Sensor.cpp
@@ -21,6 +21,8 @@
 
 /* maximum delay: 1000ms */
 const int64_t kMaxDelay = 1000000000;
+/* Gravitational acceleration constant in m/s^2 */
+const float Sensor::kGravitationalAcceleration = 9.81f;
 
 Sensor::Sensor() : acquisitionThread(nullptr), handle(-1), type(-1), delay(kMaxDelay) {}
 
diff --git a/peripheral/sensors/edison_arduino/Sensor.hpp b/peripheral/sensors/edison_arduino/Sensor.hpp
index a1c2663..d28a398 100644
--- a/peripheral/sensors/edison_arduino/Sensor.hpp
+++ b/peripheral/sensors/edison_arduino/Sensor.hpp
@@ -118,6 +118,11 @@ class Sensor {
      */
     int64_t getDelay() { return delay; }
 
+    /**
+     * Gravitational acceleration constant in m/s^2
+     */
+    static const float kGravitationalAcceleration;
+
   protected:
 
     /**
diff --git a/peripheral/sensors/edison_arduino/sensors/MMA7660Accelerometer.cpp b/peripheral/sensors/edison_arduino/sensors/MMA7660Accelerometer.cpp
index c63ffaa..0947b25 100644
--- a/peripheral/sensors/edison_arduino/sensors/MMA7660Accelerometer.cpp
+++ b/peripheral/sensors/edison_arduino/sensors/MMA7660Accelerometer.cpp
@@ -45,6 +45,9 @@ MMA7660Accelerometer::~MMA7660Accelerometer() {}
 
 int MMA7660Accelerometer::pollEvents(sensors_event_t* data, int count) {
   getAcceleration(&data->acceleration.x, &data->acceleration.y, &data->acceleration.z);
+  data->acceleration.x *= Sensor::kGravitationalAcceleration;
+  data->acceleration.y *= Sensor::kGravitationalAcceleration;
+  data->acceleration.z *= Sensor::kGravitationalAcceleration;
   return 1;
 }
 
diff --git a/peripheral/sensors/edison_arduino/sensors/MPU9150Accelerometer.cpp b/peripheral/sensors/edison_arduino/sensors/MPU9150Accelerometer.cpp
index 446de3c..f8ba355 100644
--- a/peripheral/sensors/edison_arduino/sensors/MPU9150Accelerometer.cpp
+++ b/peripheral/sensors/edison_arduino/sensors/MPU9150Accelerometer.cpp
@@ -47,6 +47,9 @@ MPU9150Accelerometer::~MPU9150Accelerometer() {}
 int MPU9150Accelerometer::pollEvents(sensors_event_t* data, int count) {
   update();
   getAccelerometer(&data->acceleration.x, &data->acceleration.y, &data->acceleration.z);
+  data->acceleration.x *= Sensor::kGravitationalAcceleration;
+  data->acceleration.y *= Sensor::kGravitationalAcceleration;
+  data->acceleration.z *= Sensor::kGravitationalAcceleration;
   return 1;
 }