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EtherCAT Cyclic Application

6. Developing IgH Applications​

6.3 Basic Structure of a Cyclic Task​

The following simplified call sequence illustrates how the master API is used:

while (running) {
    clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME,
                    &wakeup_time, NULL);

    ecrt_master_receive(master);
    ecrt_domain_process(domain);

    /* Read inputs from domain_pd with EC_READ_*(). */
    /* Run the device state machine and control algorithm. */
    /* Write outputs to domain_pd with EC_WRITE_*(). */

    ecrt_domain_queue(domain);
    ecrt_master_send(master);
}

When using DC, set the application time and synchronize the clocks at the correct point in the cycle:

ecrt_master_application_time(master, app_time_ns);
ecrt_master_sync_reference_clock_to(master, app_time_ns);
ecrt_master_sync_slave_clocks(master);

The specific synchronization method depends on the reference clock, slave capabilities, and control period. Refer to the IgH API documentation and slave manual.

6.4 Building an Application​

If IgH is installed in /opt/etherlab:

gcc main.c -o ethercat_app \
  -I/opt/etherlab/include \
  -L/opt/etherlab/lib \
  -Wl,-rpath,/opt/etherlab/lib \
  -lethercat -lpthread

For cross-compilation, use the target platform compiler and ensure that the headers and libethercat.so come from the same IgH build.