Zumo 32U4 Bootloader not working

My zumo won’t enter bootloader mode. When the reset is pressed twice within .75sec, nothing happens. At least, the yellow LED will not turn on and I cannot get my laptop to recognize it. I’ve tried following the reviving section in the user guide, but the bootloader will not activate. I’ve tried restarting my computer, arduino IDE, unplugging everything, replacing batteries, etc all to no avail. The blue LEDs do still turn on when the switched to on and the green LED also turns on when plugged into the computer.


Are you sure the USB cables you are using have data lines (e.g. have you used them for communicating with devices before)? Some USB cables are only intended to be used for charging and do not have the necessary communication lines. Can you try using a different USB cable (one that you know is working) and a different USB port to see if that fixes the issue?

- Amanda

Hey Amanda, I was uploading code just fine with the same cable right before this happened. I’ve also tried several other cables that I know have data lines. The Zumo continues to be unresponsive.

Did you try using a different USB port? Is the Zumo connected directly to your computer or connected through a USB hub? What operating system are you using? Was the Zumo working before? Has the Zumo ever been programmed with an AVR ISP programmer?

- Amanda

I am using a Mac running Windows. I’ve tried different hubs and ports. Still no luck. The Zumo was working prior to all of this. I have not programmed it with an AVR ISP programmer.

At this point, it seems either the USB connection or the yellow LED is damaged on your Zumo 32U4. To be sure, can you connect your Zumo 32U4 directly to one of your Mac’s USB ports, then press the reset button twice (within 750 ms) again while looking at the Device Manager to see if anything changes?

If nothing changes in the Device Manager, please email us directly at support@pololu.com with your order information and a reference to this thread, and we can see what we can do to help you out.

- Amanda