ESP32 Forum

Posted: **Tue Nov 14, 2023 10:10 pm**

I'm trying to modify the GATT SPP server demo to accommodate a 128-bit UUID so I can replicate other SPP profiles. While I successfully got a 128 bit service ID to work using the github client documentation and other questions on the forum, I'm having trouble making a Rx and Tx characteristic with 128 bit UUIDs.

I changed the actual receive characteristic from the following, where SPP_DATA_RECEIVE is 16b

Code: Select all

static const uint16_t spp_data_receive_uuid = ESP_GATT_UUID_SPP_DATA_RECEIVE;
static const uint8_t  spp_data_receive_val[20] = {0x00};

to

Code: Select all

static uint8_t gatts_rx_uuid128[ESP_UUID_LEN_128] = {0x9E, 0xCA, 0xDC, 0x24, 0x0E, 0xE5, 0xA9, 0xE0, 0x93, 0xF3, 0xA3, 0xB5, 0x02, 0x00, 0x40, 0x6E};
static const uint8_t  spp_data_receive_val[20] = {0x00};

In the GATT database, I changed

Code: Select all

    //SPP -  data receive characteristic Declaration
    [SPP_IDX_SPP_DATA_RECV_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}},

    //SPP -  data receive characteristic Value
    [SPP_IDX_SPP_DATA_RECV_VAL]             	=
    {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&spp_data_receive_uuid, ESP_GATT_PERM_READ|ESP_GATT_PERM_WRITE,
    SPP_DATA_MAX_LEN,sizeof(spp_data_receive_val), (uint8_t *)spp_data_receive_val}},

to

Code: Select all

    //SPP -  data receive characteristic Declaration
    [SPP_IDX_SPP_DATA_RECV_CHAR]            =
    {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_128, (uint8_t *)&character_declaration_uuid, ESP_GATT_PERM_READ,
    CHAR_DECLARATION_SIZE,CHAR_DECLARATION_SIZE, (uint8_t *)&char_prop_read_write}},

    //SPP -  data receive characteristic Value
    [SPP_IDX_SPP_DATA_RECV_VAL]             	=
    {{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_128, (uint8_t *)&gatts_rx_uuid128, ESP_GATT_PERM_READ|ESP_GATT_PERM_WRITE,
    SPP_DATA_MAX_LEN,sizeof(spp_data_receive_val), (uint8_t *)spp_data_receive_val}},

To try and account for the longer UUID.. but now it doesn't come up when I perform a scan with my mobile app. Any suggestions?

ESP32 Forum

128-bit UUID on GATT server

128-bit UUID on GATT server