RE: Bluetooth profile common characteristics between services

Sigurd — Wed, 10 Mar 2021 13:11:35 GMT

[quote user="TomDavies"]You say that if the characterisitc have different UUID then this isn't an issue[/quote]

Since the Service base is different, then it should be possible for the central to distinguish e.g. Characteristic C used in Service 2 from the one used in Service 4, even if the 16 bit UUID is the same.

I did some quick testing, I modified the lbs(LED Button Service) 16 bits UUIDs to match the ones used in NUS(Nordic UART service), and then added added lbs to the ble_app_uart example, and I did not experience any issues when testing with a Android phone as central. But, if you run into issues during your testing, then I guess it's easy to change the 16 bit UUIDs to be unique when used in different services, but I think you should be OK. If you see any issues when testing this, then let me know.

RE: Bluetooth profile common characteristics between services

Tom — Tue, 23 Feb 2021 11:56:43 GMT

Hi Sigurd,

Thanks for your response. You say that if the characterisitc have different UUID then this isn't an issue but from my description:

[quote userid="88838" url="~/f/nordic-q-a/71782/bluetooth-profile-common-characteristics-between-services"]Characteristic C does not use the same base UUID as Service 2 or 4 - I gave it a different base as it is shared but does have the same UUID when used in Service 2 and 4.[/quote]

Characteristic C does have the same UUID in Service 2 and 4.

Maybe my description wasn't the best, to expand this is what I proposed in the example with UUIDs for each

Product Apple - Service 1 (UUID 0xAAAA0000AAAAAAAAAAAAAAAAAAAAAAAA) - Characteristic A (UUID 0x0001)
                                                                    - Characteristic B (UUID 0x0002)
                Service 2 (UUID 0xBBBB0000BBBBBBBBBBBBBBBBBBBBBBBB) - Characteristic C (UUID 0xZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ)
                                                                    - Characteristic D (UUID 0x0001)
                Service 3 (UUID 0xCCCC0000CCCCCCCCCCCCCCCCCCCCCCCC) - Characteristic E (UUID 0x0001)

Product Banana- Service 1 (UUID 0xAAAA0000AAAAAAAAAAAAAAAAAAAAAAAA) - Characteristic A (UUID 0x0001)
                                                                      Characteristic B (UUID 0x0002)
                Service 4 (UUID 0xDDDD0000DDDDDDDDDDDDDDDDDDDDDDDD) - Characteristic F (UUID 0x0001)
                                                                    - Characteristic G (UUID 0x0002)
                                                                    - Characteristic C (UUID 0xZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ)

So to clarify, from your response should I change the UUID for Characteristic C from 0xZZ..ZZ to follow the base ID for each Service and use a 16 bit unique for that service? ie:

Product Apple - Service 1 (UUID 0xAAAA0000AAAAAAAAAAAAAAAAAAAAAAAA) - Characteristic A (UUID 0x0001)
                                                                    - Characteristic B (UUID 0x0002)
                Service 2 (UUID 0xBBBB0000BBBBBBBBBBBBBBBBBBBBBBBB) - Characteristic C (UUID 0x0002)
                                                                    - Characteristic D (UUID 0x0001)
                Service 3 (UUID 0xCCCC0000CCCCCCCCCCCCCCCCCCCCCCCC) - Characteristic E (UUID 0x0001)

Product Banana- Service 1 (UUID 0xAAAA0000AAAAAAAAAAAAAAAAAAAAAAAA) - Characteristic A (UUID 0x0001)
                                                                      Characteristic B (UUID 0x0002)
                Service 4 (UUID 0xDDDD0000DDDDDDDDDDDDDDDDDDDDDDDD) - Characteristic F (UUID 0x0001)
                                                                    - Characteristic G (UUID 0x0002)
                                                                    - Characteristic C (UUID 0x0003)

My thinking had been that given the characterstic was the same when used in different services it should have the same UUID. Should it instead be unique within each service, even if the characteristic is essentially duplicated?

RE: Bluetooth profile common characteristics between services

Sigurd — Mon, 22 Feb 2021 16:17:50 GMT

Hi,

Your approach seems fine. Since the characteristic have a different UUID when it's used in e.g. service 2 and 4, it shouldn't be any issues.