Onethinx LoRaWAN module comes with an integrated unique DevEUI. This number is unique for every individual module. Onethinx has its own MAC address block used for the DevEUI, registered with the IEEE Registration Authority. That way you are certain you have a unique DevEUI for your device, in the entire world. There are several ways to extract the DevEUI.
One way would be to use OpenOCD. We have made a program in C# in Visual Studio which utilizes OpenOCD to read the DevEUI from Flash. It can be found on our Github page.
Another way to extract it is from code by calling LoRaWAN_GetInfo(&coreInfo) which returns the DevEUI in the coreInfo structure. You can then use UART or any other protocol to extract it.
In order to use the internal DevEUI in your device, you need to delete the default DevEUI key and write the following.
.OTAA_10x.DevEui = thisDevEUI,
Using internal DevEUI:
Using external DevEUI: