EtherCAT Master (SOEM / IgH)

The end of an EtherCAT bus that issues commands and gathers data, usually running on the main control computer.

EtherCAT is a real-time industrial bus built on Ethernet, with one master and a number of slaves on the network: the slaves are devices such as joint drivers and sensors, and the master sends out a data frame every fixed cycle, reading and writing each slave's data in turn. Commercial masters include Beckhoff's TwinCAT; the two most common open-source options are SOEM (Simple Open EtherCAT Master), a user-space C library that's easy to get started with, and IgH EtherCAT Master (the EtherLab project), which runs as a Linux kernel module and offers better real-time performance. Humanoid and legged robots commonly run IgH or SOEM on Linux patched with PREEMPT_RT, sending commands to each joint at roughly 1 kHz.

ExampleOn the main controller, use SOEM to scan 12 joint drivers on the bus, switch them into CSP mode, and send a target position while reading back encoder values every 1 ms.

Also called

SOEM, IgH EtherCAT Master

Related

EtherCAT (Ethernet for Control Automation Technology) · PREEMPT_RT · Cyclic Synchronous Position / Velocity / Torque Modes (CiA 402) · Servo Drive (Motor Driver) · Hard Real-Time · CANopen / CiA 402 Drive Profile

Sources

SOEM GitHub
IgH EtherCAT Master（EtherLab）