EtherCAT Troubleshooting

Real-Time Optimization and Debugging

7.6 Common Problems

/dev/EtherCAT0 Cannot Be Found

Check:

lsmod | grep '^ec_'
dmesg | grep -i ethercat
modinfo ec_master

Confirm that the master module exactly matches the running kernel version, and check whether the device-node rules or master service ran correctly.

The Master Exists but Cannot Scan Any Slaves

• Check the MAC address and the interface bound to the master.
• Check slave power, IN/OUT direction, and Ethernet cables.
• When using ec_generic, confirm that the standard network driver works and normal network services do not use the interface. When using a native or platform-specific driver, confirm that the standard network driver does not occupy the device.
• Check the link speed; EtherCAT devices generally use 100 Mbit/s full duplex.
• Start troubleshooting with one slave and one short Ethernet cable.

A Slave Remains in PREOP

• Use ethercat slaves -v to display the AL state and error code.
• Check the PDO assignment and Sync Manager configuration.
• Check whether SDO initialization succeeded.
• Verify the Vendor ID, Product Code, and Revision Number.

A Slave Remains in SAFEOP

• Check whether the application has started cyclic communication.
• Check whether the working counter is complete.
• Check the watchdog, cycle period, DC, and Sync0/Sync1 configuration.
• Check whether output PDOs are initialized as required by the device.

Cycle Jitter Is High

• Confirm that PREEMPT_RT and a suitable real-time network driver are used.
• Check whether other tasks or IRQs preempt the real-time thread.
• Check CPU frequency scaling, thermal throttling, and deep sleep states.
• Remove logging, memory allocation, and blocking calls from the cyclic thread.
• Test the system with no load, one slave, and the complete topology separately.

ethercat Cannot Load libethercat.so

ldd "$(command -v ethercat)"
ldconfig -p | grep libethercat

Install the library in a system library directory and run ldconfig, or configure the runtime library search path correctly. Do not mix tools, libraries, headers, and kernel modules from different IgH versions.