unsigned int sample_size;
};
-static unsigned int partition(float* list, unsigned int left,
- unsigned int right, unsigned int pivot_index)
+
+static unsigned int partition ( float* list, unsigned int left,
+ unsigned int right, unsigned int pivot_index)
{
unsigned int i;
unsigned int store_index = left;
float aux;
float pivot_value = list[pivot_index];
- // swap list[pivotIndex] and list[right]
+ /* Swap list[pivotIndex] and list[right] */
aux = list[pivot_index];
list[pivot_index] = list[right];
list[right] = aux;
{
if (list[i] < pivot_value)
{
- // swap list[store_index] and list[i]
+ /* Swap list[store_index] and list[i] */
aux = list[store_index];
list[store_index] = list[i];
list[i] = aux;
store_index++;
}
}
- //swap list[right] and list[store_index]
+
+ /* Swap list[right] and list[store_index] */
aux = list[right];
list[right] = list[store_index];
list[store_index] = aux;
return store_index;
}
-/* http://en.wikipedia.org/wiki/Quickselect */
-float median(float* queue, unsigned int size)
+
+static float median (float* queue, unsigned int size)
{
+ /* http://en.wikipedia.org/wiki/Quickselect */
+
unsigned int left = 0;
unsigned int right = size - 1;
unsigned int pivot_index;
return temp[left];
}
-void denoise_median_init(int s, unsigned int num_fields,
- unsigned int max_samples)
+
+static void denoise_median_init(int s, unsigned int num_fields,
+ unsigned int max_samples)
{
- struct filter_median* f_data = (struct filter_median*) calloc(1, sizeof(struct filter_median));
+ struct filter_median* f_data = (struct filter_median*) calloc(1,
+ sizeof(struct filter_median));
+
f_data->buff = (float*)calloc(max_samples,
sizeof(float) * num_fields);
f_data->sample_size = max_samples;
sensor_info[s].filter = f_data;
}
-void denoise_median_release(int s)
+
+static void denoise_median_reset (struct sensor_info_t* info)
{
- if (!sensor_info[s].filter)
+ struct filter_median* f_data = (struct filter_median*) info->filter;
+
+ if (!f_data)
return;
- free(((struct filter_median*)sensor_info[s].filter)->buff);
- free(sensor_info[s].filter);
- sensor_info[s].filter = NULL;
+ f_data->count = 0;
+ f_data->idx = 0;
}
-void denoise_median(struct sensor_info_t* info, struct sensors_event_t* data,
- unsigned int num_fields)
+
+static void denoise_median ( struct sensor_info_t* info,
+ struct sensors_event_t* data,
+ unsigned int num_fields)
{
float x, y, z;
float scale;
if (!f_data)
return;
+ /* If we are at event count 1 reset the indices */
+ if (info->event_count == 1)
+ denoise_median_reset(info);
if (f_data->count < f_data->sample_size)
f_data->count++;
}
+static void denoise_average ( struct sensor_info_t* si,
+ struct sensors_event_t* data,
+ 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;
+ int f;
+ int sampling_rate = (int) si->sampling_rate;
+ int history_size;
+ int history_full = 0;
+
+ /* Don't denoise anything if we have less than two samples per second */
+ if (sampling_rate < 2)
+ return;
+
+ /* 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;
+
+ /* Reset history if we're operating on an incorrect window size */
+ if (si->history_size != history_size) {
+ si->history_size = history_size;
+ si->history_entries = 0;
+ si->history_index = 0;
+ si->history = (float*) realloc(si->history,
+ si->history_size * num_fields * sizeof(float));
+ if (si->history) {
+ si->history_sum = (float*) realloc(si->history_sum,
+ num_fields * sizeof(float));
+ if (si->history_sum)
+ memset(si->history_sum, 0, num_fields * sizeof(float));
+ }
+ }
+
+ if (!si->history || !si->history_sum)
+ return; /* Unlikely, but still... */
+
+ /* Update initialized samples count */
+ if (si->history_entries < si->history_size)
+ si->history_entries++;
+ else
+ history_full = 1;
+
+ /* Record new sample and calculate the moving sum */
+ for (f=0; f < num_fields; f++) {
+ /**
+ * A field is going to be overwritten if
+ * history is full, so decrease the history sum
+ */
+ if (history_full)
+ si->history_sum[f] -=
+ si->history[si->history_index * num_fields + f];
+
+ si->history[si->history_index * num_fields + f] = data->data[f];
+ si->history_sum[f] += data->data[f];
+
+ /* For now simply compute a mobile mean for each field */
+ /* and output filtered data */
+ data->data[f] = si->history_sum[f] / si->history_entries;
+ }
+
+ /* Update our rolling index (next evicted cell) */
+ si->history_index = (si->history_index + 1) % si->history_size;
+}
+
+
+void setup_noise_filtering (int s)
+{
+ switch (sensor_info[s].type) {
+ case SENSOR_TYPE_GYROSCOPE:
+ case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
+ denoise_median_init(s, 3, 5);
+ break;
+ }
+}
+
+
+void denoise (int s, struct sensors_event_t* data)
+{
+ switch (sensor_info[s].type) {
+ case SENSOR_TYPE_GYROSCOPE:
+ case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
+ denoise_median(&sensor_info[s], data, 3);
+ break;
+
+ case SENSOR_TYPE_MAGNETIC_FIELD:
+ denoise_average(&sensor_info[s], data, 3 , 20);
+ break;
+ }
+}
+
+
+void release_noise_filtering_data (int s)
+{
+ void *buff;
+
+ /* Delete moving average structures */
+ if (sensor_info[s].history) {
+ free(sensor_info[s].history);
+ sensor_info[s].history = NULL;
+ sensor_info[s].history_size = 0;
+ if (sensor_info[s].history_sum) {
+ free(sensor_info[s].history_sum);
+ sensor_info[s].history_sum = NULL;
+ }
+ }
+
+ /* Delete median filter structures */
+ if (sensor_info[s].filter) {
+ buff = ((struct filter_median*)sensor_info[s].filter)->buff;
+
+ if (buff)
+ free(buff);
+
+ free(sensor_info[s].filter);
+ sensor_info[s].filter = NULL;
+ }
+}
+
+
#define GLOBAL_HISTORY_SIZE 100
struct recorded_sample_t
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