The SAMR21-XPRO has an EDBG chip with a unique 64-bit MAC Address stored on each light. The SAMR21G18A MCU reads the MAC address on start-up from the EDBG chip and stores it in the internal flash (auxiliary page) when the light application is initialized for the first time. Subsequently, in case the light is reset and initializes, the MAC address is read from the internal flash.