iio-sensors: support conversion matrix magnetic field

With the prop hal.sensors.iio.magn.matrix=f1x,f1y,f1z,f2x,f2y,f2z,f3x,f3y,f3z
it is possible to manipulate the sensors directions and assignment to the
corresponding axes. The default is
hal.sensors.iio.magn.matrix=1,0,0,0,1,0,0,0,1

diff --git a/iio-sensors.cpp b/iio-sensors.cpp
index 126cb92..ca50c91 100644 (file)
--- a/iio-sensors.cpp
+++ b/iio-sensors.cpp
@@ -280,10 +280,21 @@ template<> int Sensor<ID_MAGNETIC_FIELD>::readEvents(sensors_event_t *data, int
        static float scale_y = (*nodes)[1] ? read_sysfs_float((*nodes)[1]) : scale_x;
        static float scale_z = (*nodes)[2] ? read_sysfs_float((*nodes)[2]) : scale_x;
        int ret = SensorBase::readEvents(data, cnt);
+       char cm[PROPERTY_VALUE_MAX];
+       float m[9];
+       int v[3];
+
+       property_get("hal.sensors.iio.magn.matrix", cm, "1,0,0,0,1,0,0,0,1" );
+       sscanf(cm, "%f,%f,%f,%f,%f,%f,%f,%f,%f", &m[0], &m[1], &m[2], &m[3], &m[4], &m[5], &m[6], &m[7], &m[8]);
+
        for (int i = 0; i < ret; ++i) {
-               data[i].magnetic.x = scale_x * read_sysfs_int("in_magn_x_raw");
-               data[i].magnetic.y = scale_y * read_sysfs_int("in_magn_y_raw");
-               data[i].magnetic.z = scale_z * read_sysfs_int("in_magn_z_raw");
+               v[0] = read_sysfs_int("in_magn_x_raw");
+               v[1] = read_sysfs_int("in_magn_y_raw");
+               v[2] = read_sysfs_int("in_magn_z_raw");
+               // create matrix * vector product
+               data[i].magnetic.x = scale_x * (m[0] * v[0] + m[1] * v[1] + m[2] * v[2]);
+               data[i].magnetic.y = scale_y * (m[3] * v[0] + m[4] * v[1] + m[5] * v[2]);
+               data[i].magnetic.z = scale_z * (m[6] * v[0] + m[7] * v[1] + m[8] * v[2]);
                data[i].magnetic.status = SENSOR_STATUS_ACCURACY_HIGH;
        }
        return ret;