esp-idf/examples/bluetooth/bluedroid/ble/gatt_client

Supported Targets	ESP32	ESP32-C3

ESP-IDF Gatt Client Example

This example shows how to use ESP APIs to create a GATT Client.

How to Use Example

Before project configuration and build, be sure to set the correct chip target using:

idf.py set-target <chip_name>

To test this example, you first run the gatt_server_demo, which creates services and starts advertising. Gatt_client_demo will start scanning and connect to the gatt_server_demo automatically.

This example will enable gatt server's notification function once the connection is established and then the devices start exchanging data.

Please, check this tutorial for more information about this example.

Hardware Required

• A development board with ESP32/ESP32-C3 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
• A USB cable for Power supply and programming

See Development Boards for more information about it.

Build and Flash

Run idf.py -p PORT flash monitor to build, flash and monitor the project.

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Settings for UUID128

This example works with UUID16 as default. To change to UUID128, follow this steps:

1. Change the UIID16 to UUID128. You can change the UUID according to your needs.

// Create a new UUID128 (using random values for this example)
static uint8_t gatts_xxx_uuid128[ESP_UUID_LEN_128] = {0x06, 0x18, 0x7a, 0xec, 0xbe, 0x11, 0x11, 0xea, 0x00, 0x16, 0x02, 0x42, 0x01, 0x13, 0x00, 0x04};

By adding this new UUID128, you can remove the #define macros with the old UUID16.

2. Change the structure to:

static esp_bt_uuid_t xxx_uuid = {
    .len = ESP_UUID_LEN_128,
    .uuid = {.uuid128 = { 0 },},
};

3. Add the new UUID128 to the profile.

// Copy the new UUID128 to the profile
memcpy(xxx_uuid.uuid.uuid128, gatts_xxx_uuid128, ESP_UUID_LEN_128);

4. Edit the ESP_GATTC_SEARCH_RES_EVT in order to filter the new UUID128.

case ESP_GATTC_SEARCH_RES_EVT: {
    ESP_LOGI(GATTC_TAG, "SEARCH RES: conn_id = %x is primary service %d", p_data->search_res.conn_id, p_data->search_res.is_primary);
    ESP_LOGI(GATTC_TAG, "start handle %d end handle %d current handle value %d", p_data->search_res.start_handle, p_data->search_res.end_handle, p_data->search_res.srvc_id.inst_id);
    if (p_data->search_res.srvc_id.uuid.len == ESP_UUID_LEN_128) {
        if(memcmp(p_data->search_res.srvc_id.uuid.uuid.uuid128, gatts_xxx_uuid128, ESP_UUID_LEN_128) == 0){
            ESP_LOGI(GATTC_TAG, "service uuid128 found");
            get_server = true;
            gl_profile_tab[PROFILE_X_APP_ID].service_start_handle = p_data->search_res.start_handle;
            gl_profile_tab[PROFILE_X_APP_ID].service_end_handle = p_data->search_res.end_handle;
        } else {
            ESP_LOGE(GATTC_TAG, "service not found");
        }
    }
    break;

Example Output

I (0) cpu_start: Starting scheduler on APP CPU.
I (525) BTDM_INIT: BT controller compile version [1342a48]
I (525) system_api: Base MAC address is not set
I (525) system_api: read default base MAC address from EFUSE
I (535) phy_init: phy_version 4670,719f9f6,Feb 18 2021,17:07:07
I (945) GATTC_DEMO: REG_EVT
I (955) GATTC_DEMO: scan start success
I (1115) GATTC_DEMO: 08 ef 3b a7 04 41 
I (1115) GATTC_DEMO: searched Adv Data Len 9, Scan Response Len 15
I (1115) GATTC_DEMO: searched Device Name Len 13
I (1125) GATTC_DEMO: LG CM2760(41)
I (1125) GATTC_DEMO: 

I (1425) GATTC_DEMO: 08 ef 3b a7 04 41 
I (1425) GATTC_DEMO: searched Adv Data Len 9, Scan Response Len 15
I (1425) GATTC_DEMO: searched Device Name Len 13
I (1435) GATTC_DEMO: LG CM2760(41)
I (1435) GATTC_DEMO: 

I (1865) GATTC_DEMO: 38 68 a4 69 bb 7c 
I (1865) GATTC_DEMO: searched Adv Data Len 31, Scan Response Len 14
I (1865) GATTC_DEMO: searched Device Name Len 0
I (1875) GATTC_DEMO: 

I (2185) GATTC_DEMO: 38 68 a4 69 bb 7c 
I (2185) GATTC_DEMO: searched Adv Data Len 31, Scan Response Len 14
I (2185) GATTC_DEMO: searched Device Name Len 0
I (2185) GATTC_DEMO:

Troubleshooting

For any technical queries, please open an issue on GitHub. We will get back to you soon.