Custom EtherCAT device

I have absolutley no knowlidge of the CIA402 protocol, and i have no drives

May be worth look at this
github.com/kubabuda/ecat_servo

If you ask me you should clone his repo. I think there is not much activity there and some fixes have been submitted, but none if them were implemented or at least commented on why not

I found this.. A bit misleading. There is no servo code there only the implementation for CIA. This is based on easycat library, its the same as mine. I only ported it to STM32Cube. But yes ok I see it has 402 implementation. Ehat I don't understand is why is there an extra module for linuxcnc to use the CiA protocol.. Isn't this only a definition of the PDOs?

Dominc's cia402 comp is here  github.com/dbraun1981/hal-cia402
It correctly sequences the startup steps and provides a method for homing. I think he had absolute encoders on his drives to his solution home to.

The homing method does not work using internal homing where home sensors are attached to the drive.

The solution is to rewrite the homing sequence in homing.c so that all the intermediate steps done by Linuxcnc homing are skipped and just wait until the drive says I am homed.

Homing is now a replaceable module set in the InI file or on the linuxcnc command line and you can write your own homing module so homing.c is not modified
Start here:  linuxcnc.org/docs/2.9/html/man/man9/homecomp.9.html

they have entire reference designs and most of those mcu are below $30, thats hardly expensive, unless you expect free