why does GATT use Characteristic

RE: why does GATT use Characteristic

cocoa — Wed, 30 Jul 2014 14:52:02 GMT

It would be interesting to have a comment about low duty cycle directed advertising, LL ping, L2CAP CoC, etc... by Nordic.

RE: why does GATT use Characteristic

Ulrich Myhre — Tue, 29 Jul 2014 18:54:00 GMT

It is actually optional to implement any of the new 4.1 features, meaning a 4.0 device with a few parameter tweaks would become "4.1 compliant" in a sense. So it's up to each vendor if they want to implement low duty cycle directed advertising, LL ping, L2CAP CoC, etc. Hoping to see the L2CAP communication in the future though!

RE: why does GATT use Characteristic

cocoa — Tue, 29 Jul 2014 07:47:20 GMT

In BLE version 4.1 specifications was been introduced L2CAP Connection Oriented and Dedicated Channels, that might means a non-GATT profiles or other protocols in additions to ATT and SMP.

See this Nordic ULP and this on stackoverflow .

S130 soft device should be 4.1 compliant.

-c

RE: why does GATT use Characteristic

Ulrich Myhre — Mon, 28 Jul 2014 05:41:27 GMT

This is purely due to how the core spec defines it, as you probably know :)

The characteristic declaration in the table exists mainly because it should be possible to discover the database layout and still keep the actual values locked by permission settings. GATT defines that all declarations should be readable, but the value handles can have varying permission settings through authorization or authentication.

A declaration itself also has its own UUID saying what it is (e.g. 0x2803 for characteristic), meaning it is possible to enumerate every (primary/secondary) service or every characteristic in relatively few messages. It would of course be possible to simply skip the declaration part and strip out the metadata once asked for it, but you would have to introduce some concept of "sub-UUIDs" to preserve the same functionality you have today.