gyro-calibration.c

   1 /*
   2  * Copyright (C) 2014 Intel Corporation.
   3  */
   4
   5 #include <stdio.h>
   6 #include <math.h>
   7 #include <sys/time.h>
   8 #include <utils/Log.h>
   9 #include <hardware/sensors.h>
  10 #include "common.h"
  11 #include "calibration.h"
  12
  13 static void reset (struct gyro_cal* cal_data)
  14 {
  15         cal_data->count = 0;
  16
  17         cal_data->bias_x = cal_data->bias_y = cal_data->bias_z = 0;
  18
  19         cal_data->min_x  = cal_data->min_y  = cal_data->min_z  = 1.0;
  20         cal_data->max_x  = cal_data->max_y  = cal_data->max_z  =-1.0;
  21 }
  22
  23
  24 void gyro_cal_init (struct sensor_info_t* info)
  25 {
  26         int ret;
  27         struct gyro_cal* cal_data = (struct gyro_cal*) info->cal_data;
  28         FILE* data_file;
  29
  30         info->cal_level = 0;
  31
  32         if (cal_data == NULL)
  33                 return;
  34
  35         reset(cal_data);
  36
  37         data_file = fopen (GYRO_CALIBRATION_PATH, "r");
  38         if (data_file == NULL)
  39                 return;
  40
  41         ret = fscanf(data_file, "%f %f %f",
  42                         &cal_data->bias_x, &cal_data->bias_y, &cal_data->bias_z);
  43         fclose(data_file);
  44 }
  45
  46 void gyro_store_data (struct sensor_info_t* info)
  47 {
  48         int ret;
  49         struct gyro_cal* cal_data = (struct gyro_cal*) info->cal_data;
  50         FILE* data_file;
  51
  52         if (cal_data == NULL)
  53                 return;
  54
  55         data_file = fopen (GYRO_CALIBRATION_PATH, "w");
  56
  57         if (data_file == NULL)
  58                 return;
  59
  60         ret = fprintf(data_file, "%f %f %f",
  61                 cal_data->bias_x, cal_data->bias_y, cal_data->bias_z);
  62
  63         if (ret < 0)
  64                 ALOGE ("Gyro calibration - store data failed!");
  65
  66         fclose(data_file);
  67 }
  68
  69
  70 static int gyro_collect (float x, float y, float z, struct gyro_cal* cal_data)
  71 {
  72         /* Analyze gyroscope data */
  73
  74         if (fabs(x) >= 1 || fabs(y) >= 1 || fabs(z) >= 1) {
  75
  76                 /* We're supposed to be standing still ; start over */
  77                 reset(cal_data);
  78
  79                 return 0; /* Uncalibrated */
  80         }
  81
  82         if (cal_data->count < GYRO_DS_SIZE) {
  83
  84                 if (x < cal_data->min_x)
  85                         cal_data->min_x = x;
  86
  87                 if (y < cal_data->min_y)
  88                         cal_data->min_y = y;
  89
  90                 if (z < cal_data->min_z)
  91                         cal_data->min_z = z;
  92
  93                 if (x > cal_data->max_x)
  94                         cal_data->max_x = x;
  95
  96                 if (y > cal_data->max_y)
  97                         cal_data->max_y = y;
  98
  99                 if (z > cal_data->max_z)
 100                         cal_data->max_z = z;
 101
 102                 if (fabs(cal_data->max_x - cal_data->min_x) <= GYRO_MAX_ERR &&
 103                     fabs(cal_data->max_y - cal_data->min_y) <= GYRO_MAX_ERR &&
 104                     fabs(cal_data->max_z - cal_data->min_z) <= GYRO_MAX_ERR)
 105                         cal_data->count++; /* One more conformant sample */
 106                 else
 107                         reset(cal_data); /* Out of spec sample ; start over */
 108
 109                 return 0; /* Still uncalibrated */
 110         }
 111
 112         /* We got enough stable samples to estimate gyroscope bias */
 113         cal_data->bias_x = (cal_data->max_x + cal_data->min_x) / 2;
 114         cal_data->bias_y = (cal_data->max_y + cal_data->min_y) / 2;
 115         cal_data->bias_z = (cal_data->max_z + cal_data->min_z) / 2;
 116
 117         return 1; /* Calibrated! */
 118 }
 119
 120 void calibrate_gyro(struct sensors_event_t* event, struct sensor_info_t* info)
 121 {
 122         struct gyro_cal* cal_data = (struct gyro_cal*) info->cal_data;
 123
 124         if (cal_data == NULL)
 125                 return;
 126
 127         /* Attempt gyroscope calibration if we have not reached this state */
 128         if (info->cal_level == 0)
 129                 info->cal_level = gyro_collect(event->data[0], event->data[1],
 130                                                event->data[2], cal_data);
 131
 132         switch (event->type) {
 133                 case SENSOR_TYPE_GYROSCOPE:
 134                         /* For the gyroscope apply the bias */
 135                         event->data[0] = event->data[0] - cal_data->bias_x;
 136                         event->data[1] = event->data[1] - cal_data->bias_y;
 137                         event->data[2] = event->data[2] - cal_data->bias_z;
 138
 139                         if (info->cal_level)
 140                                event->gyro.status = SENSOR_STATUS_ACCURACY_HIGH;
 141                         break;
 142
 143                 case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
 144                         /*
 145                          * For the uncalibrated gyroscope don't apply the bias,
 146                          * but tell he Android framework what we think it is.
 147                          */
 148                         event->uncalibrated_gyro.bias[0] = cal_data->bias_x;
 149                         event->uncalibrated_gyro.bias[1] = cal_data->bias_y;
 150                         event->uncalibrated_gyro.bias[2] = cal_data->bias_z;
 151                         break;
 152         }
 153 }