Store magnetometer calibration in flash

app/src/applications/compass/compass_app.c

@@ -15,6 +15,7 @@ static void compass_app_stop(void);
 
 // Functions related to app functionality
 static void timer_callback(lv_timer_t *timer);
+static void on_start_calibration(void);
 
 LV_IMG_DECLARE(move);
 
@@ -31,13 +32,9 @@ static uint32_t cal_start_ms;
 
 static void compass_app_start(lv_obj_t *root, lv_group_t *group)
 {
-    compass_ui_show(root);
+    compass_ui_show(root, on_start_calibration);
     refresh_timer = lv_timer_create(timer_callback, CONFIG_DEFAULT_CONFIGURATION_COMPASS_REFRESH_INTERVAL_MS,  NULL);
     zsw_magnetometer_set_enable(true);
-    zsw_magnetometer_start_calibration();
-    is_calibrating = true;
-    cal_start_ms = lv_tick_get();
-    zsw_popup_show("Calibration", "Spin around 360 degrees for 10.", NULL, 100, false);
 }
 
 static void compass_app_stop(void)
@@ -51,6 +48,15 @@ static void compass_app_stop(void)
     }
 }
 
+static void on_start_calibration(void)
+{
+    zsw_magnetometer_start_calibration();
+    is_calibrating = true;
+    cal_start_ms = lv_tick_get();
+    zsw_popup_show("Calibration",
+                   "Spin the watch around 360 degrees\nand do some random rotations in 3D space for 10 seconds.", NULL, 10, false);
+}
+
 static void timer_callback(lv_timer_t *timer)
 {
     if (is_calibrating &&

app/src/applications/compass/compass_ui.c

@@ -7,8 +7,20 @@ static lv_obj_t *compass_panel;
 static lv_obj_t *compass_img;
 static lv_obj_t *compass_label;
 
+static on_start_calibraion_cb_t start_cal;
+
+static void calibrate_button_event_cb(lv_event_t *e)
+{
+    if (start_cal) {
+        start_cal();
+    }
+}
+
 static void create_ui(lv_obj_t *parent)
 {
+    lv_obj_t *cal_btn;
+    lv_obj_t *cal_btn_label;
+
     LV_IMG_DECLARE(cardinal_point)
     compass_panel = lv_obj_create(parent);
     lv_obj_set_width(compass_panel, 240);
@@ -19,6 +31,16 @@ static void create_ui(lv_obj_t *parent)
     lv_obj_set_style_bg_opa(compass_panel, LV_OPA_TRANSP, LV_PART_MAIN | LV_STATE_DEFAULT);
     lv_obj_set_style_border_width(compass_panel, 0, LV_PART_MAIN | LV_STATE_DEFAULT);
 
+    cal_btn = lv_btn_create(compass_panel);
+    lv_obj_set_style_pad_all(cal_btn, 3, LV_PART_MAIN);
+    lv_obj_set_align(cal_btn, LV_ALIGN_CENTER);
+    lv_obj_set_pos(cal_btn, 0, 80);
+    lv_obj_set_size(cal_btn, 70, 25);
+    lv_obj_set_style_bg_color(cal_btn, lv_palette_main(LV_PALETTE_ORANGE), LV_PART_MAIN | LV_STATE_DEFAULT);
+    cal_btn_label = lv_label_create(cal_btn);
+    lv_label_set_text(cal_btn_label, "Calibrate");
+    lv_obj_add_event_cb(cal_btn, calibrate_button_event_cb, LV_EVENT_CLICKED, NULL);
+
     compass_img = lv_img_create(compass_panel);
     lv_img_set_src(compass_img, &cardinal_point);
     lv_obj_set_width(compass_img, LV_SIZE_CONTENT);
@@ -36,7 +58,7 @@ static void create_ui(lv_obj_t *parent)
     lv_obj_set_style_text_opa(compass_label, 255, LV_PART_MAIN | LV_STATE_DEFAULT);
 }
 
-void compass_ui_show(lv_obj_t *root)
+void compass_ui_show(lv_obj_t *root, on_start_calibraion_cb_t start_cal_cb)
 {
     assert(root_page == NULL);
 
@@ -48,6 +70,8 @@ void compass_ui_show(lv_obj_t *root)
     lv_obj_set_size(root_page, LV_PCT(100), LV_PCT(100));
     lv_obj_clear_flag(root_page, LV_OBJ_FLAG_SCROLLABLE);
 
+    start_cal = start_cal_cb;
+
     create_ui(root_page);
 }
 

app/src/applications/compass/compass_ui.h

@@ -3,7 +3,9 @@
 #include <inttypes.h>
 #include <lvgl.h>
 
-void compass_ui_show(lv_obj_t *root);
+typedef void(*on_start_calibraion_cb_t)(void);
+
+void compass_ui_show(lv_obj_t *root, on_start_calibraion_cb_t start_cal_cb);
 
 void compass_ui_remove(void);
 

app/src/sensors/zsw_magnetometer.c

@@ -1,6 +1,7 @@
 #include <zephyr/kernel.h>
 #include <zephyr/device.h>
 #include <zephyr/drivers/sensor.h>
+#include <zephyr/settings/settings.h>
 #include <zephyr/pm/pm.h>
 #include <zephyr/pm/device.h>
 #include <zephyr/pm/policy.h>
@@ -19,6 +20,16 @@ LOG_MODULE_REGISTER(zsw_magnetometer, CONFIG_ZSW_SENSORS_LOG_LEVEL);
 #define M_PI        3.14159265358979323846
 #endif
 
+#define SETTINGS_NAME_MAGN              "magn"
+#define SETTINGS_KEY_CALIB              "calibr"
+#define SETTINGS_MAGN_CALIB             SETTINGS_NAME_MAGN "/" SETTINGS_KEY_CALIB
+
+typedef struct {
+    float offset_x;
+    float offset_y;
+    float offset_z;
+} magn_calib_data_t;
+
 static double last_heading;
 static double last_x;
 static double last_y;
@@ -30,9 +41,7 @@ static double min_x;
 static double min_y;
 static double min_z;
 static bool is_calibrating;
-static float offset_x;
-static float offset_y;
-static float offset_z;
+static magn_calib_data_t calibration_data;
 
 static void zbus_periodic_slow_callback(const struct zbus_channel *chan);
 
@@ -116,22 +125,50 @@ static void lis2mdl_trigger_handler(const struct device *dev,
         }
     }
 
-    last_x = last_x - offset_x;
-    last_y = last_y - offset_y;
-    last_z = last_z - offset_z;
+    last_x = last_x - calibration_data.offset_x;
+    last_y = last_y - calibration_data.offset_y;
+    last_z = last_z - calibration_data.offset_z;
 
     last_heading = xyz_to_rotation(last_x, last_y, last_z);
 
     LOG_DBG("Rotation: %f", last_heading);
 }
 
+static int magn_cal_load(const char *p_key, size_t len,
+                         settings_read_cb read_cb, void *p_cb_arg, void *p_param)
+{
+    ARG_UNUSED(p_key);
+
+    if (len != sizeof(magn_calib_data_t)) {
+        LOG_ERR("Invalid length of magn calibration data");
+        return -EINVAL;
+    }
+
+    if (read_cb(p_cb_arg, &calibration_data, len) != sizeof(magn_calib_data_t)) {
+        LOG_ERR("Error reading magn calibration data");
+        return -EIO;
+    }
+
+    return 0;
+}
+
 int zsw_magnetometer_init(void)
 {
     if (!device_is_ready(magnetometer)) {
         LOG_ERR("Device magnetometer is not ready");
         return -ENODEV;
     }
 
+    if (settings_subsys_init()) {
+        LOG_ERR("Error during settings_subsys_init!");
+        return -EFAULT;
+    }
+
+    if (settings_load_subtree_direct(SETTINGS_MAGN_CALIB, magn_cal_load, NULL)) {
+        LOG_ERR("Error during settings_load_subtree!");
+        return -EFAULT;
+    }
+
     struct sensor_trigger trig;
     struct sensor_value odr_attr;
 
@@ -205,9 +242,11 @@ int zsw_magnetometer_stop_calibration(void)
     }
 
     is_calibrating = false;
-    offset_x = (max_x + min_x) / 2;
-    offset_y = (max_y + min_y) / 2;
-    offset_z = (max_z + min_z) / 2;
+    calibration_data.offset_x = (max_x + min_x) / 2;
+    calibration_data.offset_y = (max_y + min_y) / 2;
+    calibration_data.offset_z = (max_z + min_z) / 2;
+
+    settings_save_one(SETTINGS_MAGN_CALIB, &calibration_data, sizeof(magn_calib_data_t));
 
     return 0;
 }