Cordio MTU/ACL sizing confusion

I am trying to understand the basic Cordio stack (target: NRF52), and also adjust the default/desired MTU sizes.

Question 1
What components are actually used in the (default) setup of the Cordio stack on the nRF52 target. I see 3:

  • Cordio
  • Cordio-LL
  • Cordio-LL-nrf52840
    Each of these components has mbed_lib.json files with settings that seem to be duplicated, which leads to the 2nd question…

Question 2
I’d like to make use of a 256-byte user data payload for a given attribute. Looking at the lib.json(s), I have been able to track down 4 settings that related to this:

  1. cordio.desired-att-mtu
  2. cordio.rx-acl-buffer-size (which needs to be X bytes larger than desired-att-mtu)?
  3. cordio-ll.max-acl-size
  4. cordio-ll-nrf52840.max-acl-size

(3) and (4) of this list is where I started to become confused. Do these settings also need to be increased to match the cordio parent settings?

Any guidance on this would be much appreciated


Is the Cordio team active in answering any of these questions?