MAC Address Issues

Hi All

I have working with a FEZ Cobra for a few months developing a C# app. Although I read much of the documentation I never picked up that these boards do not ship with their correct MAC address, and these need to be applied to the device via MFDeploy.

Yesterday I started uploading my application to three new FEZ Cobras. The first device had a MAC address of:


which I recognised as this was the same MAC address used in my test device. I used MFDeploy to update the MAC address to the one printed on the sticker and rebooted the device which worked.

I then tried to do the same on another new device, and noticed that it had a default MAC address of 00-00-00-00-00-00. I updated it using MFDeploy which seemed to work, but when I restarted the device it had gone back to the default of 00. I then updated my software to set the MAC address, but the device is still not holding this MAC?

Out of 4 devices, only 2 are retaining the MAC address I set?
Why would two new devices have different default MAC addresses?
And why aren’t the MAC addresses set at the factory?

Any help appreciated!

Those devices probably have outdated tinybooter or corrupted configuration. Please reflash your device.

Hi Gus

All of the devices where re-flashed to v4.1.8 prior to installing the software.

I had to do this as my test device had been running 4.1.6, and the three new devices came installed with 4.1.7.

When I updated my GHI SDK installation it turned out the Dll’s where version 4.1.8 so I needed to udpated both my Dll’s and the devices.

I will try flashing them again to see if it makes any difference.


Hi again Gus

I have re-flashed the device but it still seems to be loosing its MAC randomly. I haven’t been able to pin it down to set sequence of events. I had a feeling it might have something to do with a failed deploy of the software, but I just had it running for a few minutes and restarted the device to find it had lost the MAC again.

Could an issue with the on-board battery cause this sort of behaviour?


Writing to flash is power critical so it is possible that flash write would fail with unstable/weak power.