basic central tutorial please

RE: basic central tutorial please

PingISTL — Wed, 08 Jun 2022 14:07:16 GMT

no problem, thanks for your help!

Ping

RE: basic central tutorial please

Kenneth — Wed, 08 Jun 2022 13:36:21 GMT

You ask legit quesitons, but it's kind of out of the scope of the tech support we provide to tutor developers on how BLE works and designed, we provide examples that show various usage, and you should from looking at the example implementation get some understanding on how it works, but you still need to also look at other sources for knowledge on how BLE is and how it can be used.

Kenneth

RE: basic central tutorial please

PingISTL — Wed, 08 Jun 2022 12:55:20 GMT

Thank you for reply, Kenneth

I am developing a central application, and needs to connect to peripherals which are connectable and exchange data, You are right there are some peripherals don't advertising services or anything, in that case there is no need to discovery anything and that is not what I am discussing here.

Please advise further on how to implement BLE profile and service specification, I need to start from a simple application like how to talk to peripheralLBS example? and need to make it generic later. I am not sure what I need to do after discovery of the ATT[ ] & handles.

Your input is much appreciated.

Ping

RE: basic central tutorial please

Kenneth — Wed, 08 Jun 2022 12:39:16 GMT

It's really up to you how you implement and do this.

If you are implementing a BLE profile, then you need to follow the BLE profile and service specification as specified by bluetooth.

If you are implementing a proprieatary BLE application, then you can do this whatever you like (e.g. there is no need to put any UUID in the advertisment if you don't want to).

Best regards,
Kenneth

RE: basic central tutorial please

PingISTL — Wed, 08 Jun 2022 10:23:44 GMT

hello, Kenneth

Thanks for your reply!

About 3 - SDP, I tried a few examples and had a bit of understanding, but I am still not sure the completer procedure to exchange data between connected peers, here is the procedure by my understanding and questions too, correct me if I am wrong please.

1. Central does active scan and get peripheral's service UUID it advertises, the UUID can be passed to bt_gatt_dm_start() function and find all services, so peripheral must advertising its service UUID, some peripheral advertising more than 1 UUID, is this right? in the case of it advertise more than 1 service UUID, gatt_discovery() need to do discover for each UUID?

2. Central initiate connection and then call gatt_discovery() function using the service UUID it scanned, and here is the print out of the central uart sample by bt_gatt_dm_data_print(dm) function.

ATT[1]:     UUID: 0x2803    Handle: 0x0011    Value:

Characteristic: 0x6e400003-b5a3-f393-e0a9-e50e24dcca9e    Properties: 0x0010

ATT[2]:     UUID: 0x6e400003-b5a3-f393-e0a9-e50e24dcca9e    Handle: 0x0012    Value:

ATT[3]:     UUID: 0x2902    Handle: 0x0013    Value:

    CCCD

ATT[4]:     UUID: 0x2803    Handle: 0x0014    Value:

Characteristic: 0x6e400002-b5a3-f393-e0a9-e50e24dcca9e    Properties: 0x000C

ATT[5]:     UUID: 0x6e400002-b5a3-f393-e0a9-e50e24dcca9e    Handle: 0x0015    Value:

3. Then probably need to define client to get the handles? like this bt_nus_handles_assign(dm, nus)? But different client seems have different client definition, the BAS service client have a different definition with NUS, so I am not sure how to make the client generic to access handles for all? please advise.

Thank you for your patience .

Ping

RE: basic central tutorial please

Kenneth — Thu, 02 Jun 2022 08:55:04 GMT

1. Optional.

2. It is common that a central take the initiative to establish an encrypted link (by bonding/pairing), but it can be initiated by a security request also from the peripheral. It's also possible that neither want to bond or encrypt the link.

3. It is common that the database discovery done by either peers are generic, there are software modules that can do this for you. I believe the central examples show how this can be done, though it can also be done by a peripheral.

Kenneth

RE: basic central tutorial please

PingISTL — Wed, 01 Jun 2022 15:17:59 GMT

Thanks, Kenneth

Read the first link and have a few questions to ask:

1. About the security feature, it seems that the central set a higher security level immediately after connection, is this optional or mandatory?

2. Is it determined by peripheral or by central only?

3. About service discovery - gatt_discovery, if central doesn't know anything (service ID) before doing discovery, how this can be done? I am aiming to do a generic central and presume it knows nothing and all information can be found by doing some sort of service discovery, am I right?

Thank you!

Ping

RE: basic central tutorial please

PingISTL — Wed, 01 Jun 2022 12:21:29 GMT

Thank you, Kenneth

I will have a look.

Ping

RE: basic central tutorial please

Kenneth — Wed, 01 Jun 2022 11:59:34 GMT

Have you looked at:
https://devzone.nordicsemi.com/guides/nrf-connect-sdk-guides/b/software/posts/building-a-ble-application-on-ncs-sdk---contrasting-to-softdevice-based-ble-applications---part-2-central-role

Also check out:
https://webinars.nordicsemi.com/developing-bluetooth-low-energy-6

And in general developing with NCS: https://academy.nordicsemi.com/

Kenneth