Can you do GATT caching with a 4.2 server and a 5.1 client?

RE: Can you do GATT caching with a 4.2 server and a 5.1 client?

Andres — Mon, 15 Nov 2021 15:45:27 GMT

Kenneth,

Thank you for your helpful answers.

Andres

RE: Can you do GATT caching with a 4.2 server and a 5.1 client?

Kenneth — Wed, 10 Nov 2021 09:55:54 GMT

[quote user="aaguirre"]You raise an interesting point, is it correct that a softdevice that supports BLE 5.1 will still not be able to handle GATT caching?[/quote]

It's an optional feature, so you are right.

[quote user="aaguirre"]Is there a document that may explain more about what features Nordic supports for BLE 5.1?[/quote]

You would need to go into the main page of each of the softdevice specifications to get the hightligthed supported features, e.g.:
https://infocenter.nordicsemi.com/topic/sds_s132/SDS/s1xx/s130.html

I think it's the second time I have seen a request for GATT caching so it doesn't seem as feature that is much used, so I guess the additional softdevice size, development and test time have not been prioritized as important enough to go into a softdevice release (at least not yet).

I am not sure if I have a quick fix for you either, you could possible do it the other way around, e.g. that the mobile phone is the GATT server and the nRF is the GATT client, then you could potentially do some "shortcuts", for instance if you reconnect to a previously connected mobile phone you can read a specific characteristic directly from the nRF to "see" if the GATT table have changed.

Kenneth

RE: Can you do GATT caching with a 4.2 server and a 5.1 client?

Andres — Tue, 09 Nov 2021 14:50:16 GMT

Hi Kenneth,

Our product does not support bonding. And it is going to be very difficult to upgrade to a recent softdevice for a number of reasons.

My next option is the source of my question, namely, continue with a softdevice which supports BLE 4.2 and find out if a central running BLE 5.1 will be able to do the GATT caching.

You raise an interesting point, is it correct that a softdevice that supports BLE 5.1 will still not be able to handle GATT caching? Is there a document that may explain more about what features Nordic supports for BLE 5.1?

Thank you,

Andres

RE: Can you do GATT caching with a 4.2 server and a 5.1 client?

Kenneth — Tue, 09 Nov 2021 14:03:55 GMT

Hello,

Are you sure GATT caching is the feature you are looking for? If your product support bonding this is indirectly already covered by the fact that the peer devices should for instance cache the system attributes and re-enable them when the link is re-encrypted, and thereby will already know the GATT table of the peer device and can for instance receive notifications without doing a new discovery of the GATT table. The only advantage of GATT caching is if your product are not supporting bonding, then GATT caching can be used to avoid re-encrypting the link after connection, thereby saving a few connection intervals on each re-connection, overall I think GATT caching is not used much, and it is (afaik) not supported by any nordic softdevice. This means that for any re-connection with a peer that does not support bonding you will need to do a new GATT table discovery, this is the default case.

Best regards,
Kenneth