GMIN-2992: Don't be as heavy handed with gyro filtering as compass

The gyroscope is not so noisy, so limit ourselves to a smaller
window size in the interest of better response time.

Issue: GMIN-2992

Change-Id: Ida74cae999007eca90c708ccf35cd3f6c706f04c
Signed-off-by: Patrick Porlan <patrick.porlan@intel.com>

diff --git a/transform.c b/transform.c
index e86fe1a..be4a8f1 100644 (file)
--- a/transform.c
+++ b/transform.c
@@ -189,8 +189,14 @@ static void reorder_fields(float* data,    unsigned char map[MAX_CHANNELS])
 
 
 static void denoise (struct sensor_info_t* si, struct sensors_event_t* data,
-                    int num_fields)
+                    int num_fields, int max_samples)
 {
+       /*
+        * Smooth out incoming data using a moving average over a number of
+        * samples. We accumulate one second worth of samples, or max_samples,
+        * depending on which is lower.
+        */
+
        int i;
        float total;
        int f;
@@ -201,9 +207,9 @@ static void denoise (struct sensor_info_t* si, struct sensors_event_t* data,
        if (sampling_rate < 2)
                return;
 
-       /* Restrict window size in case of a very high sampling rate */
-       if (sampling_rate > 100)
-               history_size = 100;
+       /* Restrict window size to the min of sampling_rate and max_samples */
+       if (sampling_rate > max_samples)
+               history_size = max_samples;
        else
                history_size = sampling_rate;
 
@@ -255,20 +261,20 @@ static int finalize_sample_default(int s, struct sensors_event_t* data)
        switch (sensor_type) {
                case SENSOR_TYPE_ACCELEROMETER:
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise(&sensor_info[s], data, 3, 20);
                        break;
 
                case SENSOR_TYPE_MAGNETIC_FIELD:
                        calibrate_compass (data, &sensor_info[s], get_timestamp());
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise(&sensor_info[s], data, 3, 100);
                        break;
 
                case SENSOR_TYPE_GYROSCOPE:
                case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
                        calibrate_gyro(data, &sensor_info[s]);
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise(&sensor_info[s], data, 3, 20);
                        break;
 
                case SENSOR_TYPE_LIGHT: