iotivity constrained is an implementation of ocf standard for really constrained hardware (MCU)
sources can be downloaded from :
git clone https://gerrit.iotivity.org/gerrit/iotivity-constrained
It's trivial to build for linux or tizen, smaller OSes : Zephyr, RIOT and contiki are supported too.
For reference check:
Note that iotivity core (csdk) can also be deployed to some MCU hardware but flash footprint is much more. Anyway one example is explained at: