#include "common.h"
#include "calibration.h"
-
-void gyro_cal_init(struct sensor_info_t* info)
+static void reset (struct gyro_cal* cal_data)
{
- info->cal_level = 0;
+ cal_data->count = 0;
- struct gyro_cal* gyro_data = (struct gyro_cal*) info->cal_data;
+ cal_data->bias_x = cal_data->bias_y = cal_data->bias_z = 0;
- if (gyro_data == NULL)
- return;
+ cal_data->min_x = cal_data->min_y = cal_data->min_z = 1.0;
+ cal_data->max_x = cal_data->max_y = cal_data->max_z =-1.0;
+}
+
+
+void gyro_cal_init (struct sensor_info_t* info)
+{
+ info->cal_level = 0;
- gyro_data->start = 0;
- gyro_data->count = 0;
- gyro_data->bias[0] = gyro_data->bias[1] = gyro_data->bias[2] = 0;
+ if (info->cal_data)
+ reset((struct gyro_cal*) info->cal_data);
}
-/* Collect points - circular queue for the last GYRO_DS_SIZE
- elements. If the points are sufficiently close compute bias */
-static void gyro_collect(float x, float y, float z, struct sensor_info_t* info)
+
+static int gyro_collect (float x, float y, float z, struct gyro_cal* cal_data)
{
- int offset, k;
- float min[3], max[3];
+ /* Analyze gyroscope data */
- struct gyro_cal* gyro_data = (struct gyro_cal*) info->cal_data;
+ if (fabs(x) >= 1 || fabs(y) >= 1 || fabs(z) >= 1) {
- if (gyro_data == NULL)
- return;
+ /* We're supposed to be standing still ; start over */
+ reset(cal_data);
- int pos = (gyro_data->start + gyro_data->count) % GYRO_DS_SIZE;
- gyro_data->sample[pos][0] = x;
- gyro_data->sample[pos][1] = y;
- gyro_data->sample[pos][2] = z;
-
- if (gyro_data->count < GYRO_DS_SIZE)
- gyro_data->count++;
- else
- gyro_data->start = (gyro_data->start + 1) % GYRO_DS_SIZE;
-
- for (k = 0; k < 3; k++)
- min[k] = max[k] = gyro_data->sample[gyro_data->start][k];
-
- /* Search for min-max values */
- for (offset = 1; offset < gyro_data->count; offset++) {
- int pos2 = (gyro_data->start + offset) % GYRO_DS_SIZE;
- for (k = 0; k < 3; k++) {
- if (min[k] > gyro_data->sample[pos2][k])
- min[k] = gyro_data->sample[pos2][k];
- else if (max[k] < gyro_data->sample[pos2][k])
- max[k] = gyro_data->sample[pos2][k];
- }
+ return 0; /* Uncalibrated */
}
- if (gyro_data->count == GYRO_DS_SIZE &&
- fabs(max[0] - min[0]) < GYRO_MAX_ERR &&
- fabs(max[1] - min[1]) < GYRO_MAX_ERR &&
- fabs(max[2] - min[2]) < GYRO_MAX_ERR) {
- info->cal_level = 1;
- gyro_data->bias[0] = (max[0] + min[0]) / 2;
- gyro_data->bias[1] = (max[1] + min[1]) / 2;
- gyro_data->bias[2] = (max[2] + min[2]) / 2;
+ if (cal_data->count < GYRO_DS_SIZE) {
+
+ if (x < cal_data->min_x)
+ cal_data->min_x = x;
+
+ if (y < cal_data->min_y)
+ cal_data->min_y = y;
+
+ if (z < cal_data->min_z)
+ cal_data->min_z = z;
+
+ if (x > cal_data->max_x)
+ cal_data->max_x = x;
+
+ if (y > cal_data->max_y)
+ cal_data->max_y = y;
+
+ if (z > cal_data->max_z)
+ cal_data->max_z = z;
+
+ if (fabs(cal_data->max_x - cal_data->min_x) <= GYRO_MAX_ERR &&
+ fabs(cal_data->max_y - cal_data->min_y) <= GYRO_MAX_ERR &&
+ fabs(cal_data->max_z - cal_data->min_z) <= GYRO_MAX_ERR)
+ cal_data->count++; /* One more conformant sample */
+ else
+ reset(cal_data); /* Out of spec sample ; start over */
+
+ return 0; /* Still uncalibrated */
}
+
+ /* We got enough stable samples to estimate gyroscope bias */
+ cal_data->bias_x = (cal_data->max_x + cal_data->min_x) / 2;
+ cal_data->bias_y = (cal_data->max_y + cal_data->min_y) / 2;
+ cal_data->bias_z = (cal_data->max_z + cal_data->min_z) / 2;
+
+ return 1; /* Calibrated! */
}
void calibrate_gyro(struct sensors_event_t* event, struct sensor_info_t* info)
{
- if (!info->cal_level) {
- gyro_collect(event->data[0], event->data[1], event->data[2], info);
- return;
- }
+ struct gyro_cal* cal_data = (struct gyro_cal*) info->cal_data;
- struct gyro_cal* gyro_data = (struct gyro_cal*) info->cal_data;
+ event->gyro.status = SENSOR_STATUS_ACCURACY_MEDIUM;
- if (gyro_data == NULL)
+ if (cal_data == NULL)
return;
+ /* Attempt gyroscope calibration if we have not reached this state */
+ if (info->cal_level == 0)
+ info->cal_level = gyro_collect(event->data[0], event->data[1],
+ event->data[2], cal_data);
+
+ if (info->cal_level)
+ event->gyro.status = SENSOR_STATUS_ACCURACY_HIGH;
+
switch (event->type) {
case SENSOR_TYPE_GYROSCOPE:
/* For the gyroscope apply the bias */
- event->data[0] = event->data[0] - gyro_data->bias[0];
- event->data[1] = event->data[1] - gyro_data->bias[1];
- event->data[2] = event->data[2] - gyro_data->bias[2];
+ event->data[0] = event->data[0] - cal_data->bias_x;
+ event->data[1] = event->data[1] - cal_data->bias_y;
+ event->data[2] = event->data[2] - cal_data->bias_z;
break;
case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
- /* For the uncalibrated gyroscope don't apply the bias but save it */
- event->uncalibrated_gyro.bias[0] = gyro_data->bias[0];
- event->uncalibrated_gyro.bias[1] = gyro_data->bias[1];
- event->uncalibrated_gyro.bias[2] = gyro_data->bias[2];
- break;
-
- default:
+ /*
+ * For the uncalibrated gyroscope don't apply the bias,
+ * but tell he Android framework what we think it is.
+ */
+ event->uncalibrated_gyro.bias[0] = cal_data->bias_x;
+ event->uncalibrated_gyro.bias[1] = cal_data->bias_y;
+ event->uncalibrated_gyro.bias[2] = cal_data->bias_z;
break;
}
-}
\ No newline at end of file
+}
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