#ifdef DBG_RAW_DATA
#define MAX_RAW_DATA_COUNT 2000
+#define RAW_DATA_FULL_PATH "/data/raw_compass_data_full_%d.txt"
+#define RAW_DATA_SELECTED_PATH "/data/raw_compass_data_selected_%d.txt"
static FILE *raw_data = NULL;
static FILE *raw_data_selected = NULL;
static int raw_data_count = 0;
int file_no = 0;
#endif
+/* compass defines */
+#define COMPASS_CALIBRATION_PATH "/data/compass.conf"
+#define EPSILON 0.000000001
+
+#define MAGNETIC_LOW 960 /* 31 micro tesla squared */
+#define CAL_STEPS 5
+
/* We'll have multiple calibration levels
* so that we can provide an estimation as fast as possible
*/
-static const float min_diffs[CAL_STEPS] = { 0.2, 0.4, 0.6, 1.0 };
-static const float max_sqr_errs[CAL_STEPS] = { 10.0, 8.0, 5.0, 3.5 };
-static const unsigned int lookback_counts[CAL_STEPS] = { 3, 4, 5, 6 };
+static const float min_diffs[CAL_STEPS] = {0.2, 0.25, 0.4, 0.6, 1.0 };
+static const float max_sqr_errs[CAL_STEPS] = {10.0, 10.0, 8.0, 5.0, 3.5 };
+static const unsigned int lookback_counts[CAL_STEPS] = {2, 3, 4, 5, 6 };
/* reset calibration algorithm */
-static void reset_sample (struct compass_cal* data)
+static void reset_sample (struct compass_cal_t* data)
{
int i,j;
data->sample_count = 0;
- for (i = 0; i < DS_SIZE; i++)
+ for (i = 0; i < MAGN_DS_SIZE; i++)
for (j=0; j < 3; j++)
data->sample[i][j] = 0;
+
+ data->average[0] = data->average[1] = data->average[2] = 0;
}
-static double calc_square_err (struct compass_cal* data)
+static double calc_square_err (struct compass_cal_t* data)
{
double err = 0;
double raw[3][1], result[3][1], mat_diff[3][1];
int i;
+ float stdev[3] = {0,0,0};
- for (i = 0; i < DS_SIZE; i++) {
+ for (i = 0; i < MAGN_DS_SIZE; i++) {
raw[0][0] = data->sample[i][0];
raw[1][0] = data->sample[i][1];
raw[2][0] = data->sample[i][2];
+ stdev[0] += (raw[0][0] - data->average[0]) * (raw[0][0] - data->average[0]);
+ stdev[1] += (raw[1][0] - data->average[1]) * (raw[1][0] - data->average[1]);
+ stdev[2] += (raw[2][0] - data->average[2]) * (raw[2][0] - data->average[2]);
+
substract (3, 1, raw, data->offset, mat_diff);
multiply(3, 3, 1, data->w_invert, mat_diff, result);
err += diff * diff;
}
- err /= DS_SIZE;
+
+ stdev[0] = sqrt(stdev[0] / MAGN_DS_SIZE);
+ stdev[1] = sqrt(stdev[1] / MAGN_DS_SIZE);
+ stdev[2] = sqrt(stdev[2] / MAGN_DS_SIZE);
+
+ /*
+ * A sanity check - if we have too little variation for an axis
+ * it's best to reject the calibration than risking a wrong calibration.
+ */
+ if (stdev[0] <= 1 || stdev[1] <= 1 || stdev[2] <= 1)
+ return max_sqr_errs[0];
+
+ err /= MAGN_DS_SIZE;
return err;
}
-// Given an real symmetric 3x3 matrix A, compute the eigenvalues
+/* Given an real symmetric 3x3 matrix A, compute the eigenvalues */
static void compute_eigenvalues(double mat[3][3], double* eig1, double* eig2, double* eig3)
{
double p = mat[0][1] * mat[0][1] + mat[0][2] * mat[0][2] + mat[1][2] * mat[1][2];
static int ellipsoid_fit (mat_input_t m, double offset[3][1], double w_invert[3][3], double* bfield)
{
int i;
- double h[DS_SIZE][9];
- double w[DS_SIZE][1];
- double h_trans[9][DS_SIZE];
+ double h[MAGN_DS_SIZE][9];
+ double w[MAGN_DS_SIZE][1];
+ double h_trans[9][MAGN_DS_SIZE];
double p_temp1[9][9];
- double p_temp2[9][DS_SIZE];
+ double p_temp2[9][MAGN_DS_SIZE];
double temp1[3][3], temp[3][3];
double temp1_inv[3][3];
double temp2[3][1];
double a[3][3], sqrt_evals[3][3], evecs[3][3], evecs_trans[3][3];
double evec1[3][1], evec2[3][1], evec3[3][1];
- for (i = 0; i < DS_SIZE; i++) {
+ for (i = 0; i < MAGN_DS_SIZE; i++) {
w[i][0] = m[i][0] * m[i][0];
h[i][0] = m[i][0];
h[i][1] = m[i][1];
h[i][7] = -1 * m[i][2] * m[i][2];
h[i][8] = 1;
}
- transpose (DS_SIZE, 9, h, h_trans);
- multiply (9, DS_SIZE, 9, h_trans, h, result);
+ transpose (MAGN_DS_SIZE, 9, h, h_trans);
+ multiply (9, MAGN_DS_SIZE, 9, h_trans, h, result);
invert (9, result, p_temp1);
- multiply (9, 9, DS_SIZE, p_temp1, h_trans, p_temp2);
- multiply (9, DS_SIZE, 1, p_temp2, w, p);
+ multiply (9, 9, MAGN_DS_SIZE, p_temp1, h_trans, p_temp2);
+ multiply (9, MAGN_DS_SIZE, 1, p_temp2, w, p);
temp1[0][0] = 2;
temp1[0][1] = p[3][0];
double eig1 = 0, eig2 = 0, eig3 = 0;
compute_eigenvalues(a, &eig1, &eig2, &eig3);
+ if (eig1 <=0 || eig2 <= 0 || eig3 <= 0)
+ return 0;
+
sqrt_evals[0][0] = sqrt(eig1);
sqrt_evals[1][0] = 0;
sqrt_evals[2][0] = 0;
multiply (3, 3, 3, temp1, evecs_trans, temp);
transpose (3, 3, temp, w_invert);
*bfield = pow(sqrt(1/eig1) * sqrt(1/eig2) * sqrt(1/eig3), 1.0/3.0);
+
+ if (*bfield < 0)
+ return 0;
+
multiply_scalar_inplace(3, 3, w_invert, *bfield);
return 1;
raw_data_count = 0;
#endif
- struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
-
+ struct compass_cal_t* cal_data = (struct compass_cal_t*) info->cal_data;
+ int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
+ info->max_cal_level : CAL_STEPS;
if (cal_data == NULL)
return;
&cal_data->w_invert[2][0], &cal_data->w_invert[2][1], &cal_data->w_invert[2][2],
&cal_data->bfield);
- if (ret != data_count) {
+ if (ret != data_count || info->cal_level >= cal_steps) {
info->cal_level = 0;
}
}
+
if (info->cal_level) {
ALOGV("CompassCalibration: load old data, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f",
cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0],
static void compass_store_result(FILE* data_file, struct sensor_info_t* info)
{
- struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
+ struct compass_cal_t* cal_data = (struct compass_cal_t*) info->cal_data;
if (data_file == NULL || cal_data == NULL)
return;
ALOGE ("compass calibration - store data failed!");
}
-static int compass_collect (struct sensors_event_t* event, struct sensor_info_t* info, int64_t current_time)
+static int compass_collect (struct sensors_event_t* event, struct sensor_info_t* info)
{
float data[3] = {event->magnetic.x, event->magnetic.y, event->magnetic.z};
unsigned int index,j;
unsigned int lookback_count;
float min_diff;
- struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
+ struct compass_cal_t* cal_data = (struct compass_cal_t*) info->cal_data;
if (cal_data == NULL)
return -1;
/* Discard the point if not valid */
- if (data[0] == 0 && data[1] == 0 && data[2] == 0)
+ if (data[0] == 0 || data[1] == 0 || data[2] == 0)
return -1;
#ifdef DBG_RAW_DATA
lookback_count = lookback_counts[info->cal_level];
min_diff = min_diffs[info->cal_level];
- // For the current point to be accepted, each x/y/z value must be different enough
- // to the last several collected points
- if (cal_data->sample_count > 0 && cal_data->sample_count < DS_SIZE) {
+ /*
+ * For the current point to be accepted, each x/y/z value must be different
+ * enough to the last several collected points.
+ */
+ if (cal_data->sample_count > 0 && cal_data->sample_count < MAGN_DS_SIZE) {
unsigned int lookback = lookback_count < cal_data->sample_count ? lookback_count :
cal_data->sample_count;
for (index = 0; index < lookback; index++){
}
}
- if (cal_data->sample_count < DS_SIZE) {
+ if (cal_data->sample_count < MAGN_DS_SIZE) {
memcpy(cal_data->sample[cal_data->sample_count], data, sizeof(float) * 3);
cal_data->sample_count++;
+ cal_data->average[0] += data[0];
+ cal_data->average[1] += data[1];
+ cal_data->average[2] += data[2];
ALOGV("CompassCalibration:point collected [%f,%f,%f], selected_count=%d",
(double)data[0], (double)data[1], (double)data[2], cal_data->sample_count);
#ifdef DBG_RAW_DATA
event->magnetic.y * event->magnetic.y +
event->magnetic.z * event->magnetic.z);
- sanity_norm = (sqr_norm < MAGNETIC_LOW) ? MAGNETIC_LOW : sanity_norm;
- sanity_norm = (sqr_norm > MAGNETIC_HIGH) ? MAGNETIC_HIGH : sanity_norm;
+ if (sqr_norm < MAGNETIC_LOW)
+ sanity_norm = MAGNETIC_LOW;
if (sanity_norm && sqr_norm) {
scale = sanity_norm / sqr_norm;
static void compass_compute_cal (struct sensors_event_t* event, struct sensor_info_t* info)
{
- struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
+ struct compass_cal_t* cal_data = (struct compass_cal_t*) info->cal_data;
double result[3][1], raw[3][1], diff[3][1];
if (!info->cal_level || cal_data == NULL)
int i;
float max_sqr_err;
- struct compass_cal* cal_data = (struct compass_cal*) info->cal_data;
+ struct compass_cal_t* cal_data = (struct compass_cal_t*) info->cal_data;
+ struct compass_cal_t new_cal_data;
+
+ /*
+ * Some sensors take unrealistically long to calibrate at higher levels.
+ * We'll use a max_cal_level if we have such a property setup, or go with
+ * the default settings if not.
+ */
+ int cal_steps = (info->max_cal_level && info->max_cal_level <= CAL_STEPS) ?
+ info->max_cal_level : CAL_STEPS;
- if (cal_data->sample_count < DS_SIZE)
+ if (cal_data->sample_count < MAGN_DS_SIZE)
return info->cal_level;
max_sqr_err = max_sqr_errs[info->cal_level];
- /* enough points have been collected, do the ellipsoid calibration */
- for (i = 0; i < DS_SIZE; i++) {
+ /* Enough points have been collected, do the ellipsoid calibration */
+
+ /* Compute average per axis */
+ cal_data->average[0] /= MAGN_DS_SIZE;
+ cal_data->average[1] /= MAGN_DS_SIZE;
+ cal_data->average[2] /= MAGN_DS_SIZE;
+
+ for (i = 0; i < MAGN_DS_SIZE; i++) {
mat[i][0] = cal_data->sample[i][0];
mat[i][1] = cal_data->sample[i][1];
mat[i][2] = cal_data->sample[i][2];
}
- /* check if result is good */
- struct compass_cal new_cal_data;
- /* the sample data must remain the same */
+ /* Check if result is good. The sample data must remain the same */
new_cal_data = *cal_data;
+
if (ellipsoid_fit(mat, new_cal_data.offset, new_cal_data.w_invert, &new_cal_data.bfield)) {
double new_err = calc_square_err (&new_cal_data);
ALOGI("new err is %f, max sqr err id %f", new_err,max_sqr_err);
memcpy(cal_data->offset, new_cal_data.offset, sizeof(cal_data->offset));
memcpy(cal_data->w_invert, new_cal_data.w_invert, sizeof(cal_data->w_invert));
cal_data->bfield = new_cal_data.bfield;
- if (info->cal_level < (CAL_STEPS - 1))
+ if (info->cal_level < (cal_steps - 1))
info->cal_level++;
ALOGV("CompassCalibration: ready check success, caldata: %f %f %f %f %f %f %f %f %f %f %f %f %f, err %f",
cal_data->offset[0][0], cal_data->offset[1][0], cal_data->offset[2][0], cal_data->w_invert[0][0],
return info->cal_level;
}
-void calibrate_compass (struct sensors_event_t* event, struct sensor_info_t* info, int64_t current_time)
+
+void calibrate_compass (struct sensors_event_t* event, struct sensor_info_t* info)
{
- long current_time_ms = current_time / 1000000;
int cal_level;
/* Calibration is continuous */
- compass_collect (event, info, current_time_ms);
+ compass_collect (event, info);
cal_level = compass_ready(info);
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