Change LoPy devEUI and LoRaWAN

[bnjroos]

Hi,

I know it is possible to change the LoPy devEUI by using:

fo = open("/flash/sys/lpwan.mac", "wb")
mac_write=bytes([0x01,0xb1,0xd1,0x41,0x91,0x31,0xb1,0xb4])
fo.write(mac_write)
fo.close()

I have been unable to find my answer on the internet, so I am gonna ask here, I hope it is in the right place:

• Is it authorized by the LoRaWAN specification to change a devEUI on an end node?
• Are there any restrictions or is it ok as long as we ensure that it remains unique ?

For example, in case a LoPy device is faulty and we want to field replace it with a spare one without having to register it again in the back-end.

Thank you,

[bnjroos]

@eric73 Thank you for your answer, I think it replies my question: It is possible however it depends on the network server allowed behavior.

[Eric73]

@bnjroos It's not so simple and it depend on your lorawan network provider strategy about DevNonce (and it's lorawan specification version applyed to it's base station)
PLease have a look at
https://github.com/brocaar/loraserver/issues/116
for more explication.
When a device do a join request to network, it's send a number called DevNonce (random in lorawan 1.0.x) to the network, some network store this number and a device is not allowed to re-use this number before some time/retry count (1 year ? 1 month?).
On lorawan 1.1 this number as to be incremental and stored in persitente memory inside the device.
So it depend to your lorawan network provider if this change can be working or not.