I'm working with a couple Feather 32u4 devices and I've had success so far in setting them up as transmitters and receivers as well as hooking up one of them to a Featherwing Ethernet and talking over MQTT. My problem is that I'm trying to find out how I can implement some sort of identification system among them so that I can send packets to a specific radio. The approach I'd like to avoid is that of writing different versions of the code with different IDs hardcoded in each and uploading them to a radio (so ideally I'm wondering if there's a way to access an inherent mac ID/UUID of each radio). Each radio did come with what appears to be a mac ID printed on a piece of paper but I don't know how to access that directly from the device.


  • It doesn't sound like any of the components in your system have hardware unique ID's. The ATmega does not, and if your radio does is unknowable without it being specifically identified, but most likely not given the included piece of paper. Mar 10, 2018 at 22:31
  • There are multiple boards partially named "Feather 32U4". You need to edit your question to specify which one and post a link that provides more information on it.
    – per1234
    Mar 12, 2018 at 1:25

1 Answer 1


I'm quite sure the reason they print a mac address on a sticker and put it in the package is that they have no way of storing the address in the the feather wing, or at least don't bother to do so if there is a place to store it.

It's up to you to get that address to your Ethernet.begin() call.

FYI, I have been trying to use EEPROM to store the mac address, but the bootloader appears to blow away EEPROM with every reboot. If I figure that one out I'll update.

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