RE: A question about the UUID & Characteristic ID

bjorn-spockeli — Fri, 01 Feb 2019 13:00:27 GMT

HI Lee,

Which SDK version are you using? SDK v12.3.0?

The Nordic UART Service(NUS) is a Vendor Specific Bluetooth Service, not a Bluetooth SIG Service. So you need to make the following changes:

1. Setting the UUIDs to advertise

static ble_uuid_t vive_adv_uuids[] = {{BLE_UUID_NUS_SERVICE, BLE_UUID_TYPE_BLE}}; /**< Universally unique service identifier. */

must be changed to

static ble_uuid_t vive_adv_uuids[] = {{BLE_UUID_NUS_SERVICE, BLE_UUID_TYPE_VENDOR_BEGIN}}; /**< Universally unique service identifier. */

2. Adding the Vendor Specific UUID

// Add the service.
BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_NUS_SERVICE);
err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY,&ble_uuid,&p_nus->service_handle);
if (err_code != NRF_SUCCESS)
{
    return err_code;
}

must be changed to the following

ble_uuid_t            ble_uuid;
ble_uuid128_t         nus_base_uuid = NUS_BASE_UUID;

/**@snippet [Adding proprietary Service to the SoftDevice] */
// Add a custom base UUID.
err_code = sd_ble_uuid_vs_add(&nus_base_uuid, &p_nus->uuid_type);
VERIFY_SUCCESS(err_code);

ble_uuid.type = p_nus->uuid_type;
ble_uuid.uuid = BLE_UUID_NUS_SERVICE;

// Add the service.
err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY,
                                    &ble_uuid,
                                    &p_nus->service_handle);

3. Set the correct UUID type when adding the RX and TX characteristics

The following macros,

BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_NUS_TX_CHARACTERISTIC);

BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_NUS_RX_CHARACTERISTIC);

must be replaced with

ble_uuid.type = p_nus->uuid_type;
ble_uuid.uuid = BLE_UUID_NUS_TX_CHARACTERISTIC;

ble_uuid.type = p_nus->uuid_type;
ble_uuid.uuid = BLE_UUID_NUS_RX_CHARACTERISTIC;

as shown in the snippet below

/**@brief Function for adding RX characteristic.
 *
 * @param[in] p_nus       Nordic UART Service structure.
 * @param[in] p_nus_init  Information needed to initialize the service.
 *
 * @return NRF_SUCCESS on success, otherwise an error code.
 */
static uint32_t rx_char_add(ble_nus_t * p_nus, const ble_nus_init_t * p_nus_init)
{
    /**@snippet [Adding proprietary characteristic to S110 SoftDevice] */
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_md_t cccd_md;
    ble_gatts_attr_t    attr_char_value;
    ble_uuid_t          ble_uuid;
    ble_gatts_attr_md_t attr_md;

    memset(&cccd_md, 0, sizeof(cccd_md));

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);

    cccd_md.vloc = BLE_GATTS_VLOC_STACK;

    memset(&char_md, 0, sizeof(char_md));

    char_md.char_props.notify = 1;
    char_md.p_char_user_desc  = NULL;
    char_md.p_char_pf         = NULL;
    char_md.p_user_desc_md    = NULL;
    char_md.p_cccd_md         = &cccd_md;
    char_md.p_sccd_md         = NULL;

    ble_uuid.type = p_nus->uuid_type;
    ble_uuid.uuid = BLE_UUID_NUS_RX_CHARACTERISTIC;

    memset(&attr_md, 0, sizeof(attr_md));

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);

    attr_md.vloc    = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth = 0;
    attr_md.wr_auth = 0;
    attr_md.vlen    = 1;

    memset(&attr_char_value, 0, sizeof(attr_char_value));

    attr_char_value.p_uuid    = &ble_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len  = sizeof(uint8_t);
    attr_char_value.init_offs = 0;
    attr_char_value.max_len   = BLE_NUS_MAX_RX_CHAR_LEN;

    return sd_ble_gatts_characteristic_add(p_nus->service_handle,
                                           &char_md,
                                           &attr_char_value,
                                           &p_nus->rx_handles);
    /**@snippet [Adding proprietary characteristic to S110 SoftDevice] */
}


/**@brief Function for adding TX characteristic.
 *
 * @param[in] p_nus       Nordic UART Service structure.
 * @param[in] p_nus_init  Information needed to initialize the service.
 *
 * @return NRF_SUCCESS on success, otherwise an error code.
 */
static uint32_t tx_char_add(ble_nus_t * p_nus, const ble_nus_init_t * p_nus_init)
{
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_t    attr_char_value;
    ble_uuid_t          ble_uuid;
    ble_gatts_attr_md_t attr_md;

    memset(&char_md, 0, sizeof(char_md));

    char_md.char_props.write         = 1;
    char_md.char_props.write_wo_resp = 1;
    char_md.p_char_user_desc         = NULL;
    char_md.p_char_pf                = NULL;
    char_md.p_user_desc_md           = NULL;
    char_md.p_cccd_md                = NULL;
    char_md.p_sccd_md                = NULL;

    ble_uuid.type = p_nus->uuid_type;
    ble_uuid.uuid = BLE_UUID_NUS_TX_CHARACTERISTIC;

    memset(&attr_md, 0, sizeof(attr_md));

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);

    attr_md.vloc    = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth = 0;
    attr_md.wr_auth = 0;
    attr_md.vlen    = 1;

    memset(&attr_char_value, 0, sizeof(attr_char_value));

    attr_char_value.p_uuid    = &ble_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len  = 1;
    attr_char_value.init_offs = 0;
    attr_char_value.max_len   = BLE_NUS_MAX_TX_CHAR_LEN;

    return sd_ble_gatts_characteristic_add(p_nus->service_handle,
                                           &char_md,
                                           &attr_char_value,
                                           &p_nus->tx_handles);
}

Best regards
Bjørn