static void cb_gattc_register_for_notification(int conn_id, int registered, int status,
btgatt_srvc_id_t *srvc_id, btgatt_gatt_id_t *char_id);
static void cb_gattc_notify(int conn_id, btgatt_notify_params_t *p_data);
static void cb_gattc_register_for_notification(int conn_id, int registered, int status,
btgatt_srvc_id_t *srvc_id, btgatt_gatt_id_t *char_id);
static void cb_gattc_notify(int conn_id, btgatt_notify_params_t *p_data);