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

[Andres]

We have a device based on NRF52832, SDK 13.0, Softdevice S132 v4.0.5. We can't upgrade the Softdevice at this time but we can modify the firmware if necessary.

We know that Bluetooth 5.1 has a feature to allow for GATT caching to speed up the connection between the server  and the client.

If the client, e.g., a smartphone, already has Bluetooth 5.1 and the server, e.g., our device, has Bluetooth 4.2, would it still be possible to have GATT caching?

What can the 4.2 device do to tell the 5.1 smartphone to do GATT caching?

[Kenneth]

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