Connecting to peripheral BLE device using BMD 350 (nrf52 based chip) as central BLE device.

RE: Connecting to peripheral BLE device using BMD 350 (nrf52 based chip) as central BLE device.

Simonr — Fri, 11 Apr 2025 10:14:28 GMT

Check out this case that discusses how to use ble_db_discovery to find the DFU service for example. I think that should give you some intel in the issue you're seeing here.

Best regards,

Simon

RE: Connecting to peripheral BLE device using BMD 350 (nrf52 based chip) as central BLE device.

inspiringdev123 — Tue, 08 Apr 2025 15:11:17 GMT

Susheel Nuguru

I have added the following code to add the uuid.

uint8_t uuid_type;
    uint32_t err_code;
    ble_uuid128_t base_uuid = { FIXD_BASE_UUID };

    err_code = sd_ble_uuid_vs_add(&base_uuid, &uuid_type);
    APP_ERROR_CHECK(err_code);

    ble_uuid_t obd_uuids[] = 
    {
        { .uuid = BLE_UUID_LELINK_SERVICE, .type = BLE_UUID_TYPE_BLE },
        { .uuid = BLE_UUID_VLINK_SERVICE, .type = BLE_UUID_TYPE_BLE },
        { .uuid = BLE_UUID_FIXD_SERVICE, .type = uuid_type } 
    };

But after adding the uuid, the uuid type is 0x04 instead of 0x02. I cannot find anywhere that says what 0x04 for uuid type would mean after registering it? It should be 0x02 if it is vendor specific correct?

EDIT: I see in the documentation, after each call it increments the uuid type by one. I call for ble_nus and dfu so 4 makes sense since this is the third call.

But I am still getting the service not found in the discovery event callback.

RE: Connecting to peripheral BLE device using BMD 350 (nrf52 based chip) as central BLE device.

Susheel Nuguru — Tue, 08 Apr 2025 04:58:52 GMT

Hi Matt,

I can see that you are using nRF5SDK. Your discovery is failing because the FIXD device's service UUID 0xFFF0 is not a standard 16-I think your BLE UUID, it's a 128-bit vendor-specific UUID, even though it appears as 0xFFF0 in nRF Connect.

You registered it as a 16-bit UUID which you should do if the UUID is a BLE standard UUID of type BLE_UUID_TYPE_BLE .

{ .uuid = BLE_UUID_FIXD_SERVICE, .type = BLE_UUID_TYPE_BLE }

The screenshot in the nrf connect app confirms this as it seems 0XFFF0 as unknown service

In your code you have this check

(p_evt->params.discovered_db.srv_uuid.type == p_obd_service_client->uuid_type)

This check fails before BLE_UUID_TYPE_BLE != BLE_UUID_TYPE_VENDOR_BEGIN + X

You need to add a full 128 bit UUID for your FIXD service/Device something like this

#define FIXD_BASE_UUID  { 0xAB, 0xCD, 0xEF, 0x00, 0x12, 0x34, 0x56, 0x78, \
                          0x9A, 0xBC, 0xDE, 0xF0, 0xF0, 0xFF, 0x00, 0x00 }

See that 0XFFF0 is represented in your base UUID in the little endian format.

Register this to the softdevice uuid database

ble_uuid128_t base_uuid = { FIXD_BASE_UUID };
uint8_t uuid_type;

err_code = sd_ble_uuid_vs_add(&base_uuid, &uuid_type);
APP_ERROR_CHECK(err_code);
...
...
// Then when you are registering for callback for discovery event of your service, you do this
ble_uuid_t fixd_uuid;
fixd_uuid.uuid = 0xFFF0;
fixd_uuid.type = uuid_type;

err_code = ble_db_discovery_evt_register(&fixd_uuid);

You clearly need to have your uuid.type updated so that your compare in the discovery callback is comparing the right things.

p_obd_service_client->uuid_type = uuid_type;

in discovery callback you do this
if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE &&
    (p_evt->params.discovered_db.srv_uuid.uuid == BLE_UUID_FIXD_SERVICE) &&
    (p_evt->params.discovered_db.srv_uuid.type == p_obd_service_client->uuid_type))

This should work now