Device Discovery using "Read By Group Type Request"?

RE: Device Discovery using "Read By Group Type Request"?

Hung Bui — Wed, 26 Jun 2019 09:05:31 GMT

Hi Lars,

I got an update from our R&D. It could be related to an old Qualcomm issue dating 5-10 years back. I'm not sure it's the case with your printer, but would it be possible to update the stack on the printer?

If that's not possible, you may need to stick with the "generic" service discovery.

RE: Device Discovery using "Read By Group Type Request"?

laran — Fri, 14 Jun 2019 20:16:48 GMT

Yes this is exactly what I did, I used nRFConnect on Android tablet for connecting to the device, the Wireshark log is attached above. All the services are discovered properly and I can see the battery service in nRFConnect.

RE: Device Discovery using "Read By Group Type Request"?

Hung Bui — Fri, 14 Jun 2019 10:48:39 GMT

Hi Lars,

Yes unless the attribute table doesn't have that attribute with such UUID it should return with the correct location (handle) of the attribute.

Have you tried using nRFConnect to connect to the device and check if you can see the battery service ?

RE: Device Discovery using "Read By Group Type Request"?

laran — Tue, 11 Jun 2019 17:25:46 GMT

Hi Hung,

The device is a Bluetooth thermal printer (POS-5802DD) and if I interpret the log properly it looks like a Qualcomm chip. Are you suggesting that the peripheral I am using is not following the standard, since it does not answer to the "Find By Type Value Request"?

I will look into your message sequence, and see if I manage to get a full discovery working, thanks.

RE: Device Discovery using "Read By Group Type Request"?

Hung Bui — Tue, 11 Jun 2019 14:33:35 GMT

Hi Lars,

Which peripheral you are using for testing ? I assume it's a 3rd party product ?

Any device that pass Bluetooth qualification should response correctly to all ATT opcode.

Regarding your question, yes you can do a full service discovery, similar to what the Android phone did.

You can follow this message sequence chart on how to do a "full" service discovery.

Our db_discovery library currently only does service/characteristic discovery for predefined characteristics.