ESP32 reads BLE iTag's Battery Service

borch84
Posts: 10
Joined: Fri May 04, 2018 9:11 pm

ESP32 reads BLE iTag's Battery Service

Postby borch84 » Fri May 04, 2018 9:40 pm

Hello, I am using gatt client example for reading the battery level value from an Itag, which is a BLE device.
The device is:
Screen Shot 2018-05-04 at 15.17.28.png
Screen Shot 2018-05-04 at 15.17.28.png (558.12 KiB) Viewed 7970 times
I am using the nRF Connect to discover the services advertised by the iTag. As you can see, the battery service is reporting 99%
WhatsApp Image 2018-05-04 at 3.08.24 PM.jpeg
WhatsApp Image 2018-05-04 at 3.08.24 PM.jpeg (82.73 KiB) Viewed 7970 times
I have modified the gatt client code to read the service UUID from the itag.

Code: Select all

#define REMOTE_SERVICE_UUID        0x180F //iTAG battery service
#define REMOTE_NOTIFY_CHAR_UUID    0x2A19 //battery level characteristic
I found that when the esp_ble_gattc_register_for_notify funcion is called, it return 0 (cero) descriptor for the characteristic. Instead of calling for esp_ble_gattc_register_for_notify, I call instead esp_ble_gattc_read_char.

When the read funcion happens, it calls the ESP_GATTC_READ_CHAR_EVT:

Code: Select all

    
    case ESP_GATTC_READ_CHAR_EVT: {
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_READ_CHAR_EVT");
        ESP_LOGI(GATTC_TAG, "p_data->read.value %s",p_data->read.value);
        ESP_LOGI(GATTC_TAG, "p_data->read.value_len %d",p_data->read.value_len);
        break;
    }
When this part of code executes it returns the following values:

I (604) GATTC_DEMO: remote_device_name: iTAG | remote_device_name len: 4

I (604) GATTC_DEMO: adv_name_nospaces: iTAG | adv_name_nospaces len: 4

I (614) GATTC_DEMO: searched device iTAG

I (614) GATTC_DEMO: connect to the remote device.
I (624) GATTC_DEMO: stop scan successfully
I (1244) GATTC_DEMO: ESP_GATTC_CONNECT_EVT conn_id 0, if 3
I (1244) GATTC_DEMO: REMOTE BDA:
I (1244) GATTC_DEMO: ff ff c1 00 ad 3e
I (1254) GATTC_DEMO: open success
I (1724) GATTC_DEMO: ESP_GATTC_CFG_MTU_EVT, Status 0, MTU 23, conn_id 0
I (1724) GATTC_DEMO: ESP_GATTC_SEARCH_RES_EVT
I (1724) GATTC_DEMO: service found
I (1734) GATTC_DEMO: UUID16: 180f
I (1734) GATTC_DEMO: ESP_GATTC_SEARCH_CMPL_EVT
I (1744) GATTC_DEMO: attr count: 1

I (1744) GATTC_DEMO: char count: 1
I (1774) GATTC_DEMO: ESP_GATTC_READ_CHAR_EVT
I (1774) GATTC_DEMO: p_data->read.value c
I (1774) GATTC_DEMO: p_data->read.value_len 1

I am confused because I think it should return "99%", am I correct?

Maybe somebody has a better understanding of this and could point me to the correct direction. My objective is to be able to read the value "99%" from the ESP32. Thank you.

I am using the following code:

Code: Select all

/*
   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/



/****************************************************************************
*
* This file is for gatt client. It can scan ble device, connect one device.
* Run the gatt_server demo, the client demo will automatically connect to the gatt_server demo.
* Client demo will enable gatt_server's notify after connection. Then the two devices will exchange
* data.
*
****************************************************************************/

/*
#ifndef BTM_INITIAL_TRACE_LEVEL
#define BTM_INITIAL_TRACE_LEVEL BT_TRACE_LEVEL_DEBUG
#endif

#ifndef L2CAP_INITIAL_TRACE_LEVEL
#define L2CAP_INITIAL_TRACE_LEVEL BT_TRACE_LEVEL_DEBUG
#endif

#ifndef GATT_INITIAL_TRACE_LEVEL
#define GATT_INITIAL_TRACE_LEVEL BT_TRACE_LEVEL_DEBUG
#endif
*/

#include <stdint.h>
#include <string.h>
#include <stdbool.h>
#include <stdio.h>
#include "nvs.h"
#include "nvs_flash.h"
#include "controller.h"

#include "esp_bt.h"
#include "esp_gap_ble_api.h"
#include "esp_gattc_api.h"
#include "esp_gatt_defs.h"
#include "esp_bt_main.h"
#include "esp_gatt_common_api.h"

#define GATTC_TAG "GATTC_DEMO"
#define REMOTE_SERVICE_UUID        0x180F //iTAG battery service
#define REMOTE_NOTIFY_CHAR_UUID    0x2A19 //battery level characteristic
#define PROFILE_NUM      1
#define PROFILE_A_APP_ID 0
#define INVALID_HANDLE   0

//static const char remote_device_name[] = "ESP_GATTS_DEMO";
static const char remote_device_name[] = "iTAG"; //borch

static bool connect    = false;
static bool get_server = false;
static esp_gattc_char_elem_t *char_elem_result   = NULL;
static esp_gattc_descr_elem_t *descr_elem_result = NULL;

/* eclare static functions */
static void esp_gap_cb(esp_gap_ble_cb_event_t event, esp_ble_gap_cb_param_t *param);
static void esp_gattc_cb(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t *param);
static void gattc_profile_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t *param);


static esp_bt_uuid_t remote_filter_service_uuid = {
    .len = ESP_UUID_LEN_16,
    .uuid = {.uuid16 = REMOTE_SERVICE_UUID,},
};

static esp_bt_uuid_t remote_filter_char_uuid = {
    .len = ESP_UUID_LEN_16,
    .uuid = {.uuid16 = REMOTE_NOTIFY_CHAR_UUID,},
};

static esp_bt_uuid_t notify_descr_uuid = {
    .len = ESP_UUID_LEN_16,
    .uuid = {.uuid16 = ESP_GATT_UUID_CHAR_CLIENT_CONFIG,},
};

static esp_ble_scan_params_t ble_scan_params = {
    .scan_type              = BLE_SCAN_TYPE_ACTIVE,
    .own_addr_type          = BLE_ADDR_TYPE_PUBLIC,
    .scan_filter_policy     = BLE_SCAN_FILTER_ALLOW_ALL,
    .scan_interval          = 0x50,
    .scan_window            = 0x30
};

struct gattc_profile_inst {
    esp_gattc_cb_t gattc_cb;
    uint16_t gattc_if;
    uint16_t app_id;
    uint16_t conn_id;
    uint16_t service_start_handle;
    uint16_t service_end_handle;
    uint16_t char_handle;
    esp_bd_addr_t remote_bda;
};

/* One gatt-based profile one app_id and one gattc_if, this array will store the gattc_if returned by ESP_GATTS_REG_EVT */
static struct gattc_profile_inst gl_profile_tab[PROFILE_NUM] = {
    [PROFILE_A_APP_ID] = {
        .gattc_cb = gattc_profile_event_handler,
        .gattc_if = ESP_GATT_IF_NONE,       /* Not get the gatt_if, so initial is ESP_GATT_IF_NONE */
    },
};

static void gattc_profile_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t *param)
{
    esp_ble_gattc_cb_param_t *p_data = (esp_ble_gattc_cb_param_t *)param;

    switch (event) {
    case ESP_GATTC_REG_EVT:
        ESP_LOGI(GATTC_TAG, "REG_EVT");
        esp_err_t scan_ret = esp_ble_gap_set_scan_params(&ble_scan_params);
        if (scan_ret){
            ESP_LOGE(GATTC_TAG, "set scan params error, error code = %x", scan_ret);
        }
        break;
    case ESP_GATTC_CONNECT_EVT:{
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_CONNECT_EVT conn_id %d, if %d", p_data->connect.conn_id, gattc_if);
        gl_profile_tab[PROFILE_A_APP_ID].conn_id = p_data->connect.conn_id;
        memcpy(gl_profile_tab[PROFILE_A_APP_ID].remote_bda, p_data->connect.remote_bda, sizeof(esp_bd_addr_t));
        ESP_LOGI(GATTC_TAG, "REMOTE BDA:");
        esp_log_buffer_hex(GATTC_TAG, gl_profile_tab[PROFILE_A_APP_ID].remote_bda, sizeof(esp_bd_addr_t));
        esp_err_t mtu_ret = esp_ble_gattc_send_mtu_req (gattc_if, p_data->connect.conn_id);
        if (mtu_ret){
            ESP_LOGE(GATTC_TAG, "config MTU error, error code = %x", mtu_ret);
        }
        break;
    }
    case ESP_GATTC_OPEN_EVT:
        if (param->open.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG, "open failed, status %d", p_data->open.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "open success");
        break;
    case ESP_GATTC_CFG_MTU_EVT:
        if (param->cfg_mtu.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG,"config mtu failed, error status = %x", param->cfg_mtu.status);
        }
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_CFG_MTU_EVT, Status %d, MTU %d, conn_id %d", param->cfg_mtu.status, param->cfg_mtu.mtu, param->cfg_mtu.conn_id);
        esp_ble_gattc_search_service(gattc_if, param->cfg_mtu.conn_id, &remote_filter_service_uuid);
        break;
    case ESP_GATTC_SEARCH_RES_EVT: {
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_SEARCH_RES_EVT");
        esp_gatt_srvc_id_t *srvc_id =(esp_gatt_srvc_id_t *)&p_data->search_res.srvc_id;
        if (srvc_id->id.uuid.len == ESP_UUID_LEN_16 && srvc_id->id.uuid.uuid.uuid16 == REMOTE_SERVICE_UUID) {
            ESP_LOGI(GATTC_TAG, "service found");
            get_server = true;
            gl_profile_tab[PROFILE_A_APP_ID].service_start_handle = p_data->search_res.start_handle;
            gl_profile_tab[PROFILE_A_APP_ID].service_end_handle = p_data->search_res.end_handle;
            ESP_LOGI(GATTC_TAG, "UUID16: %x", srvc_id->id.uuid.uuid.uuid16);
        }
        break;
    }
    case ESP_GATTC_SEARCH_CMPL_EVT:
        if (p_data->search_cmpl.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG, "search service failed, error status = %x", p_data->search_cmpl.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_SEARCH_CMPL_EVT");
        if (get_server){
            uint16_t count = 0;
            esp_gatt_status_t status = esp_ble_gattc_get_attr_count( gattc_if,
                                                                     p_data->search_cmpl.conn_id,
                                                                     ESP_GATT_DB_CHARACTERISTIC,
                                                                     gl_profile_tab[PROFILE_A_APP_ID].service_start_handle,
                                                                     gl_profile_tab[PROFILE_A_APP_ID].service_end_handle,
                                                                     INVALID_HANDLE,
                                                                     &count);
            if (status != ESP_GATT_OK){
                ESP_LOGE(GATTC_TAG, "esp_ble_gattc_get_attr_count error");
            }
            ESP_LOGI(GATTC_TAG, "attr count: %d\n",count);
            if (count > 0){
                char_elem_result = (esp_gattc_char_elem_t *)malloc(sizeof(esp_gattc_char_elem_t) * count);
                if (!char_elem_result){
                    ESP_LOGE(GATTC_TAG, "gattc no mem");
                }else{
                    status = esp_ble_gattc_get_char_by_uuid( gattc_if,
                                                             p_data->search_cmpl.conn_id,
                                                             gl_profile_tab[PROFILE_A_APP_ID].service_start_handle,
                                                             gl_profile_tab[PROFILE_A_APP_ID].service_end_handle,
                                                             remote_filter_char_uuid,
                                                             char_elem_result,
                                                             &count);
                    if (status != ESP_GATT_OK){
                        ESP_LOGE(GATTC_TAG, "esp_ble_gattc_get_char_by_uuid error");
                    }

                    /*  Every service have only one char in our 'ESP_GATTS_DEMO' demo, so we used first 'char_elem_result' */
                    if (count > 0 && (char_elem_result[0].properties & ESP_GATT_CHAR_PROP_BIT_NOTIFY)){
                        ESP_LOGI(GATTC_TAG, "char count: %d\n",count);
                        gl_profile_tab[PROFILE_A_APP_ID].char_handle = char_elem_result[0].char_handle;

                        esp_ble_gattc_read_char(gattc_if,p_data->search_cmpl.conn_id,gl_profile_tab[PROFILE_A_APP_ID].char_handle,ESP_GATT_AUTH_REQ_NONE);

                        //esp_ble_gattc_register_for_notify (gattc_if, gl_profile_tab[PROFILE_A_APP_ID].remote_bda, char_elem_result[0].char_handle);
                    }
                }
                /* free char_elem_result */
                free(char_elem_result);
            }else{
                ESP_LOGE(GATTC_TAG, "no char found");
            }
        }
         break;

    case ESP_GATTC_READ_CHAR_EVT: {
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_READ_CHAR_EVT");
        ESP_LOGI(GATTC_TAG, "p_data->read.value %s",p_data->read.value);
        ESP_LOGI(GATTC_TAG, "p_data->read.value_len %d",p_data->read.value_len);
        break;
    }

    case ESP_GATTC_REG_FOR_NOTIFY_EVT: {
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_REG_FOR_NOTIFY_EVT");
        if (p_data->reg_for_notify.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG, "REG FOR NOTIFY failed: error status = %d", p_data->reg_for_notify.status);
        }else{
            uint16_t count = 0;
            uint16_t notify_en = 1;
            esp_gatt_status_t ret_status = esp_ble_gattc_get_attr_count( gattc_if,
                                                                         gl_profile_tab[PROFILE_A_APP_ID].conn_id,
                                                                         ESP_GATT_DB_DESCRIPTOR,
                                                                         gl_profile_tab[PROFILE_A_APP_ID].service_start_handle,
                                                                         gl_profile_tab[PROFILE_A_APP_ID].service_end_handle,
                                                                         gl_profile_tab[PROFILE_A_APP_ID].char_handle,
                                                                         &count);
            if (ret_status != ESP_GATT_OK){
                ESP_LOGE(GATTC_TAG, "esp_ble_gattc_get_attr_count error");
            }
            ESP_LOGI(GATTC_TAG, "desc count: %d\n",count);
            if (count > 0){
                descr_elem_result = malloc(sizeof(esp_gattc_descr_elem_t) * count);
                if (!descr_elem_result){
                    ESP_LOGE(GATTC_TAG, "malloc error, gattc no mem");
                }else{
                    ret_status = esp_ble_gattc_get_descr_by_char_handle( gattc_if,
                                                                         gl_profile_tab[PROFILE_A_APP_ID].conn_id,
                                                                         p_data->reg_for_notify.handle,
                                                                         notify_descr_uuid,
                                                                         descr_elem_result,
                                                                         &count);
                    if (ret_status != ESP_GATT_OK){
                        ESP_LOGE(GATTC_TAG, "esp_ble_gattc_get_descr_by_char_handle error");
                    }

                    /* Every char has only one descriptor in our 'ESP_GATTS_DEMO' demo, so we used first 'descr_elem_result' */
                    if (count > 0 && descr_elem_result[0].uuid.len == ESP_UUID_LEN_16 && descr_elem_result[0].uuid.uuid.uuid16 == ESP_GATT_UUID_CHAR_CLIENT_CONFIG){
                        ret_status = esp_ble_gattc_write_char_descr( gattc_if,
                                                                     gl_profile_tab[PROFILE_A_APP_ID].conn_id,
                                                                     descr_elem_result[0].handle,
                                                                     sizeof(notify_en),
                                                                     (uint8_t *)&notify_en,
                                                                     ESP_GATT_WRITE_TYPE_RSP,
                                                                     ESP_GATT_AUTH_REQ_NONE);
                    }

                    if (ret_status != ESP_GATT_OK){
                        ESP_LOGE(GATTC_TAG, "esp_ble_gattc_write_char_descr error");
                    }

                    /* free descr_elem_result */
                    free(descr_elem_result);
                }
            }
            else{
                ESP_LOGE(GATTC_TAG, "decsr not found");
                
            }

        }
        break;
    }
    case ESP_GATTC_NOTIFY_EVT:
        if (p_data->notify.is_notify){
            ESP_LOGI(GATTC_TAG, "ESP_GATTC_NOTIFY_EVT, receive notify value:");
        }else{
            ESP_LOGI(GATTC_TAG, "ESP_GATTC_NOTIFY_EVT, receive indicate value:");
        }
        esp_log_buffer_hex(GATTC_TAG, p_data->notify.value, p_data->notify.value_len);
        break;
    case ESP_GATTC_WRITE_DESCR_EVT:
        if (p_data->write.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG, "write descr failed, error status = %x", p_data->write.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "write descr success ");
        uint8_t write_char_data[35];
        for (int i = 0; i < sizeof(write_char_data); ++i)
        {
            write_char_data[i] = i % 256;
        }
        esp_ble_gattc_write_char( gattc_if,
                                  gl_profile_tab[PROFILE_A_APP_ID].conn_id,
                                  gl_profile_tab[PROFILE_A_APP_ID].char_handle,
                                  sizeof(write_char_data),
                                  write_char_data,
                                  ESP_GATT_WRITE_TYPE_RSP,
                                  ESP_GATT_AUTH_REQ_NONE);
        break;
    case ESP_GATTC_SRVC_CHG_EVT: {
        esp_bd_addr_t bda;
        memcpy(bda, p_data->srvc_chg.remote_bda, sizeof(esp_bd_addr_t));
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_SRVC_CHG_EVT, bd_addr:");
        esp_log_buffer_hex(GATTC_TAG, bda, sizeof(esp_bd_addr_t));
        break;
    }
    case ESP_GATTC_WRITE_CHAR_EVT:
        if (p_data->write.status != ESP_GATT_OK){
            ESP_LOGE(GATTC_TAG, "write char failed, error status = %x", p_data->write.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "write char success ");
        break;
    case ESP_GATTC_DISCONNECT_EVT:
        connect = false;
        get_server = false;
        ESP_LOGI(GATTC_TAG, "ESP_GATTC_DISCONNECT_EVT, reason = %d", p_data->disconnect.reason);
        break;
    default:
        break;
    }
}

static void esp_gap_cb(esp_gap_ble_cb_event_t event, esp_ble_gap_cb_param_t *param)
{
    uint8_t *adv_name = NULL;
    uint8_t adv_name_len = 0;
    switch (event) {
    case ESP_GAP_BLE_SCAN_PARAM_SET_COMPLETE_EVT: {
        //the unit of the duration is second
        uint32_t duration = 30;
        esp_ble_gap_start_scanning(duration);
        break;
    }
    case ESP_GAP_BLE_SCAN_START_COMPLETE_EVT:
        //scan start complete event to indicate scan start successfully or failed
        if (param->scan_start_cmpl.status != ESP_BT_STATUS_SUCCESS) {
            ESP_LOGE(GATTC_TAG, "scan start failed, error status = %x", param->scan_start_cmpl.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "scan start success");

        break;
    case ESP_GAP_BLE_SCAN_RESULT_EVT: {
        esp_ble_gap_cb_param_t *scan_result = (esp_ble_gap_cb_param_t *)param;
        switch (scan_result->scan_rst.search_evt) {
        case ESP_GAP_SEARCH_INQ_RES_EVT:
            esp_log_buffer_hex(GATTC_TAG, scan_result->scan_rst.bda, 6);
            ESP_LOGI(GATTC_TAG, "searched Adv Data Len %d, Scan Response Len %d", scan_result->scan_rst.adv_data_len, scan_result->scan_rst.scan_rsp_len);
            adv_name = esp_ble_resolve_adv_data(scan_result->scan_rst.ble_adv,
                                                ESP_BLE_AD_TYPE_NAME_CMPL, &adv_name_len);
            ESP_LOGI(GATTC_TAG, "searched Device Name Len %d", adv_name_len);
            esp_log_buffer_char(GATTC_TAG, adv_name, adv_name_len);
            ESP_LOGI(GATTC_TAG, "\n");
            if (adv_name != NULL) {

                            	
                char adv_name_nospaces[strlen(remote_device_name)];

                int i,j;	
                for ( i = 0, j = 0; i<strlen((const char*)adv_name);i++,j++) {
                    if (adv_name[i] != ' ')  
                        adv_name_nospaces[j]=adv_name[i];
                    else 
                        j--;
                }
                adv_name_nospaces[j]=0;

                ESP_LOGI(GATTC_TAG, "remote_device_name: %s | remote_device_name len: %d\n", remote_device_name,strlen(remote_device_name));
                ESP_LOGI(GATTC_TAG, "adv_name_nospaces: %s | adv_name_nospaces len: %d\n", adv_name_nospaces,strlen(adv_name_nospaces));

                //if (strlen(remote_device_name) == adv_name_len && strncmp((char *)adv_name, remote_device_name, adv_name_len) == 0) { 
                
                if ( strncmp(adv_name_nospaces, remote_device_name, strlen(adv_name_nospaces)) == 0 ) { 
                    ESP_LOGI(GATTC_TAG, "searched device %s\n", remote_device_name);
                    if (connect == false) {
                        connect = true;
                        ESP_LOGI(GATTC_TAG, "connect to the remote device.");
                        esp_ble_gap_stop_scanning();
                        esp_ble_gattc_open(gl_profile_tab[PROFILE_A_APP_ID].gattc_if, scan_result->scan_rst.bda, scan_result->scan_rst.ble_addr_type, true);

                    }
                }

            }
            break;
        case ESP_GAP_SEARCH_INQ_CMPL_EVT:
            break;
        default:
            break;
        }
        break;
    }

    case ESP_GAP_BLE_SCAN_STOP_COMPLETE_EVT:
        if (param->scan_stop_cmpl.status != ESP_BT_STATUS_SUCCESS){
            ESP_LOGE(GATTC_TAG, "scan stop failed, error status = %x", param->scan_stop_cmpl.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "stop scan successfully");
        break;

    case ESP_GAP_BLE_ADV_STOP_COMPLETE_EVT:
        if (param->adv_stop_cmpl.status != ESP_BT_STATUS_SUCCESS){
            ESP_LOGE(GATTC_TAG, "adv stop failed, error status = %x", param->adv_stop_cmpl.status);
            break;
        }
        ESP_LOGI(GATTC_TAG, "stop adv successfully");
        break;
    case ESP_GAP_BLE_UPDATE_CONN_PARAMS_EVT:
         ESP_LOGI(GATTC_TAG, "update connection params status = %d, min_int = %d, max_int = %d,conn_int = %d,latency = %d, timeout = %d",
                  param->update_conn_params.status,
                  param->update_conn_params.min_int,
                  param->update_conn_params.max_int,
                  param->update_conn_params.conn_int,
                  param->update_conn_params.latency,
                  param->update_conn_params.timeout);
        break;
    default:
        break;
    }
}

static void esp_gattc_cb(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t *param)
{
    /* If event is register event, store the gattc_if for each profile */
    if (event == ESP_GATTC_REG_EVT) {
        if (param->reg.status == ESP_GATT_OK) {
            gl_profile_tab[param->reg.app_id].gattc_if = gattc_if;
        } else {
            ESP_LOGI(GATTC_TAG, "reg app failed, app_id %04x, status %d",
                    param->reg.app_id,
                    param->reg.status);
            return;
        }
    }

    /* If the gattc_if equal to profile A, call profile A cb handler,
     * so here call each profile's callback */
    do {
        int idx;
        for (idx = 0; idx < PROFILE_NUM; idx++) {
            if (gattc_if == ESP_GATT_IF_NONE || /* ESP_GATT_IF_NONE, not specify a certain gatt_if, need to call every profile cb function */
                    gattc_if == gl_profile_tab[idx].gattc_if) {
                if (gl_profile_tab[idx].gattc_cb) {
                    gl_profile_tab[idx].gattc_cb(event, gattc_if, param);
                }
            }
        }
    } while (0);
}

void app_main()
{
    // Initialize NVS.
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK( ret );

    ESP_ERROR_CHECK(esp_bt_controller_mem_release(ESP_BT_MODE_CLASSIC_BT));

    esp_bt_controller_config_t bt_cfg = BT_CONTROLLER_INIT_CONFIG_DEFAULT();
    ret = esp_bt_controller_init(&bt_cfg);
    if (ret) {
        ESP_LOGE(GATTC_TAG, "%s initialize controller failed: %s\n", __func__, esp_err_to_name(ret));
        return;
    }

    ret = esp_bt_controller_enable(ESP_BT_MODE_BLE);
    if (ret) {
        ESP_LOGE(GATTC_TAG, "%s enable controller failed: %s\n", __func__, esp_err_to_name(ret));
        return;
    }

    ret = esp_bluedroid_init();
    if (ret) {
        ESP_LOGE(GATTC_TAG, "%s init bluetooth failed: %s\n", __func__, esp_err_to_name(ret));
        return;
    }

    ret = esp_bluedroid_enable();
    if (ret) {
        ESP_LOGE(GATTC_TAG, "%s enable bluetooth failed: %s\n", __func__, esp_err_to_name(ret));
        return;
    }

    //register the  callback function to the gap module
    ret = esp_ble_gap_register_callback(esp_gap_cb);
    if (ret){
        ESP_LOGE(GATTC_TAG, "%s gap register failed, error code = %x\n", __func__, ret);
        return;
    }

    //register the callback function to the gattc module
    ret = esp_ble_gattc_register_callback(esp_gattc_cb);
    if(ret){
        ESP_LOGE(GATTC_TAG, "%s gattc register failed, error code = %x\n", __func__, ret);
        return;
    }

    ret = esp_ble_gattc_app_register(PROFILE_A_APP_ID);
    if (ret){
        ESP_LOGE(GATTC_TAG, "%s gattc app register failed, error code = %x\n", __func__, ret);
    }
    esp_err_t local_mtu_ret = esp_ble_gatt_set_local_mtu(500);
    if (local_mtu_ret){
        ESP_LOGE(GATTC_TAG, "set local  MTU failed, error code = %x", local_mtu_ret);
    }

}


cm6000
Posts: 1
Joined: Wed May 02, 2018 10:19 am

Re: ESP32 reads BLE iTag's Battery Service

Postby cm6000 » Thu May 10, 2018 6:27 am

I am trying to do similar thing although my remote devise is different. I have the UUIDs of the service and the characteristic but when the esp_ble_gattc_read_char is called on the ESP_GATTC_READ_CHAR_EVT the status is 1 which i think mean that the handle is invalid:

case ESP_GATTC_READ_CHAR_EVT:
ESP_LOGI(GATTC_TAG, "READ CHAR EVT");
ESP_LOGI(GATTC_TAG, "p_data->read.value_len %d",p_data->read.value_len);
ESP_LOGI(GATTC_TAG, "p_data->read.status %d",p_data->read.status); //ESP_GATT_INVALID_HANDLE ???
break;

Not sure what the "handle" should be - i am using the characteristic's UUID.

WiFive
Posts: 3529
Joined: Tue Dec 01, 2015 7:35 am

Re: ESP32 reads BLE iTag's Battery Service

Postby WiFive » Thu May 10, 2018 7:38 am

Not a string a uint8
99 = 0x63 = 'c'

borch84
Posts: 10
Joined: Fri May 04, 2018 9:11 pm

Re: ESP32 reads BLE iTag's Battery Service

Postby borch84 » Thu May 17, 2018 12:59 am

Thanks! I was able to read the value:

Code: Select all

const char *char_pointer = (char*)p_data->read.value
int battery_percentage = (int)*char_pointer;
ESP_LOGI(GATTC_TAG, "(p_data->read.value) Battery level: %d %%",battery_percentage);

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