BLE : How to expose 128bits UUID of a characteristic (IDFGH-4855)

[Marc-Aurele]

Hello,

My characteristics expose only 16 bits instead of full UUID (128bits). Is there a way to expose the full UUID ?

static const uint16_t custom_svc        = 0xFF00;
static const uint16_t custom_str_uuid   = 0xFF01;
static const uint8_t custom_ccc[2]      = {0x00, 0x00};
static uint8_t  custom_str_value[10+1]  = "NULL";

#define GATTS_DEMO_CHAR_VAL_LEN_MAX 500

static const esp_gatts_attr_db_t custom_att_db[CUSTOM_IDX_NB] =
{
    /* Custom service Declaration */
    [CUSTOM_IDX_SVC]            = {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&primary_service_uuid, ESP_GATT_PERM_READ,
                                    sizeof(uint16_t), sizeof(custom_svc), (uint8_t *)&custom_svc}},

    /* Characteristic Declaration */
    [CUSTOM_IDX_CHAR]           = {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_declaration_uuid, ESP_GATT_PERM_READ,
                                    CHAR_DECLARATION_SIZE,CHAR_DECLARATION_SIZE, (uint8_t *)&char_prop_read_write_notify}},

    /* Characteristic Value */
    [CUSTOM_IDX_CHAR_VAL]       = {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&custom_str_uuid, ESP_GATT_PERM_WRITE|ESP_GATT_PERM_READ,
                                    GATTS_DEMO_CHAR_VAL_LEN_MAX, sizeof(custom_str_value), (uint8_t *)custom_str_value}},

    /* Client Characteristic Configuration Descriptor */
    [CUSTOM_IDX_CHAR_CFG]       = {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_client_config_uuid, ESP_GATT_PERM_READ | ESP_GATT_PERM_WRITE,
                                    sizeof(uint16_t), sizeof(custom_ccc), (uint8_t *)custom_ccc}},
};

Regards,

Aurélien

[chegewara]

Dou you want to have service with 128 bit UUID or advertise service with 128 bit UUID?

[Marc-Aurele]

Hi @chegewara
Once my device is paired, I want all my characteristics expose a 128 bits UUID if possible. For now, it seems my characteristics only expose a 16 bits UUID.
Regards,

[chegewara]

https://github.com/espressif/esp-idf/blob/master/examples/bluetooth/gatt_server_service_table/main/gatts_table_creat_demo.c#L92-L123

[Weijian-Espressif]

@chegewara,
thanks for your help.
@Marc-Aurele ,
Has your problem been solved?

[Marc-Aurele]

Hi all,

Thank you very much @chegewara for the proposition but i'm afraid to not understand exactly what you mean. Indeed, what i want is the following. Here are two devices :

These two devices expose custum characteristics (red border)
Mine is on the left, but as you can see, it exposes only 16 bits uuid whereas the one on the right exposes the full 128 bits uuid.
Maybe i'm missing something in the link you attached to your previous post.

Regards,

[chegewara]

https://github.com/espressif/esp-idf/blob/master/examples/bluetooth/gatt_server_service_table/main/gatts_table_creat_demo.c#L103-L104

https://github.com/espressif/esp-idf/blob/master/examples/bluetooth/gatt_server_service_table/main/gatts_table_creat_demo.c#L120-L121

If you setup it with different UUIDs then you can advertise 2 different 128bit UUIDs at the same time.
Remember this option is to use with normal advertising, if you are using raw advertising then you need to build advertising packet byte by byte.

[Marc-Aurele]

Thank you very much @chegewara ;)

[hcanak]

Hello,
I have a question about the same project (gatts_table_creat_demo.c).
I want to "advertise" service with 128 bit UUID. In the example file line 85-89 defines 128bit UUID. See below;

static uint8_t service_uuid[16] = {
/* LSB <--------------------------------------------------------------------------------> MSB */
//first uuid, 16bit, [12],[13] is the value
0xfb, 0x34, 0x9b, 0x5f, 0x80, 0x00, 0x00, 0x80, 0x00, 0x10, 0x00, 0x00, 0xFF, 0x00, 0x00, 0x00,
};

When i compile and run the project it does NOT advertise above 128bit UUID instead it advertise 2 "0x00FF" services!!!. Please see attachment of LightBlue caps.

Now, my questions;

1. Although we supplied one 128bit UUID in line 85-89, we get responce of two 16bit UUIDs (0x00FF).
   How can i get 128bit advertisement UUID?
2. When i change service_uuid[12] and service_uuid[13], it advertise that value as it said in the comment line 87. Why do we get two 16bit service UUIDs while we set only one 16bit UUID?

Thanks in advance.

[xulongzhuang]

Hello, @hcanak
First, the two UUIDs are displayed because the broadcast data and scan response data are configured at the same time. You can remove esp_ble_gap_config_adv_data(&scan_rsp_data) or esp_ble_gap_config_scan_rsp_data_raw(raw_scan_rsp_data, sizeof(raw_scan_rsp_data)) to display only one service uuid.
Second, the reason why 128 bit UUID is set but only 16 bit UUID is displayed in the broadcast is the return value of the following uuidType function, The base of service_uuid is the same as BASE_UUID, so there is no need to put all 128 bit UUIDs in the broadcast, unless we change service_uuid and BASE_UUID are very different

int uuidType(unsigned char *p_uuid)
{
    int i = 0;
    int match = 0;
    int all_zero = 1;

    for (i = 0; i != 16; ++i) {
       if (i == 12 || i == 13) {
            continue;
        }  

        if (p_uuid[i] == BASE_UUID[i]) {
            ++match;
        }

        if (p_uuid[i] != 0) {
            all_zero = 0;
        }
    }
    if (all_zero) {
        return 0;
    }
    if (match == 12) {
        return LEN_UUID_32;
    }
    if (match == 14) {
        return LEN_UUID_16;
    }
    return LEN_UUID_128;
}

[HieuDAY1]

@chegewara Can you reshare the link?