EthercatDevice_XXX.getSerialNumber()

#include "Ethercat.h"

EthercatMaster master;
EthercatDevice_QECR11DF0S slave;

void setup(void) {
    uint32_t getSerialNumber;
    
    Serial.begin(115200);
    while (!Serial);
    
    master.begin();
    slave.attach(0, master);
    master.start();
    getSerialNumber = slave.getSerialNumber();
    Serial.println(getSerialNumber);
}

void loop() {}