SOES EtherCAT Slave Library, written in C, is used to write custom EtherCAT Slave applications.
SOES can run on a large number of platforms, the main requirement is that the platform include or can interface an EtherCAT Slave Controller(ESC).
It is easy to use and provides a small footprint. It is a good alternative to more complex stacks on the market and is especially well suited for embedded systems.
Full product documentation is available here (requires a free account at RT-Labs).