Custom BLE service can't read all characteristics

RE: Custom BLE service can't read all characteristics

MicSch — Wed, 21 Dec 2022 08:49:05 GMT

I found the issue. In the on_characteristic_discovery_rsp() there is BLE_GATT_DB_MAX_CHARS which limits the max amount. It is declared in ble_gatt_dh.h

RE: Custom BLE service can't read all characteristics

MicSch — Wed, 21 Dec 2022 08:29:38 GMT

Yes I modified the BLE_DB_DISCOVERY_MAX_SRV in ble_db_discovery.h

RE: Custom BLE service can't read all characteristics

Hung Bui — Wed, 21 Dec 2022 08:21:17 GMT

Hi MicSch,

Have you modified BLE_DB_DISCOVERY_MAX_SRV inside ble_db_discovery.h ?

RE: Custom BLE service can't read all characteristics

MicSch — Tue, 20 Dec 2022 16:22:22 GMT

They are indeed under the same service. I increased both, but it didn't work. BLE_GATT_DB_MAX_CHARS wasn't declared in the library or the sdk_confiq file, but it doesnt matter where I declare it?
I will try do search for the query of the ATT_READ_BY_TYPE_RSP response tomorrow, maybe this will fix the issue.

RE: Custom BLE service can't read all characteristics

Hung Bui — Tue, 20 Dec 2022 15:52:34 GMT

Hi MicSch,

I found this declaration BLE_DB_DISCOVERY_MAX_SRV set to 6 in the ble_db_discovery.h . It matched with what you observed.

Could you try to increase it ?
I'm not sure if all of your characteristic is under the same service or not, but if they are, then you need to increase BLE_GATT_DB_MAX_CHARS as well.

RE: Custom BLE service can't read all characteristics

MicSch — Tue, 20 Dec 2022 15:11:26 GMT

Hello Hung Bui,

I'm using the ble_db_discovery lib. I changed a client example to be able to discover the custom service. It's running on a nrf52832 chip. In the meantime I will try to find the query for the ATT_READ_BY_TYPE_RSP response.

Here are the two traces.

devzone.nordicsemi.com/.../snifferTraceCentral.pcapng devzone.nordicsemi.com/.../snifferTraceBleApp.pcapng

RE: Custom BLE service can't read all characteristics

Hung Bui — Tue, 20 Dec 2022 14:35:22 GMT

Hi MicSch,

Could you give more information about your central ? Did you use our service discovery library to do the task ?

Please attach the sniffer trace file so we can have a look.

My understanding is that after receiving ATT_READ_BY_TYPE_RSP and the result was not "Attribute Not Found " you would need to continue sending ATT_READ_BY_TYPE_REQ again with the start handled updated until you receive "Attribute not found" Please see Section 4.6.1 Vol 3 Part G in Bluetooth Spec.