Debugging is not supported by "Pololu A-Star 32U4'

I loaded up my sketch and I discover that debugging isn’t supported by these boards! Is there any work-around? I need the compact size for the project, but maybe there’s a board that does support debugging that I can develop on and then move to the Polulu A-Star 32U4 for the actual project?


Please note that our company name is Pololu, not “Polulu” (I have corrected it in the title of your post).

You did not mention which particular A-Star 32U4 controller you are using, but the ATmega32U4 used on those boards does have JTAG. We do not enable it by default, but if you use an ISP programmer to program the JTAGEN fuse, you should be able to use JTAG after that. However, please note that the A-Star 32U4 Micro does not break out all of the JTAG pins, so if you’re using that you might consider one of the A-Star 32U4 Mini controllers instead.


The specific reason I’m using the 32U4 Micro is the size, a board 2" long simply isn’t an option. I don’t have the JTAG programmer, I was assuming it worked over the USB interface. I’m coming from the Microchip PIC environment, quite different, still getting used to Arduino.

You could consider using an A-Star 32U4 Mini to develop a prototype, then switch to an A-Star 32U4 Micro for the final project.

Alternatively, you could consider switching to the A-Star 328PB Micro.


What’s the benefit of the A-Star 32U4 Mini over the A-Star 32U4 Micro? I like the fact that I have the USB on the Micro.

I don’t want to go to a larger board for the. project, so the A-Star 328PB Micro would not be suitable. Space is at a premium where this is going, and I already have to include a second custom PCB for power supply and I/O drivers.

As I mentioned in one of my previous posts, all of the pins necessary to use JTAG for debugging are not accessible on the A-Star 32U4 Micro, but they are on the larger A-Star 32U4 Mini boards. All 32U4 versions of the A-Star controllers including the micro and mini have USB.

The A-Star 328PB Micro (1.3" × 0.7") has slightly larger footprint than the A-Star 32U4 Micro (1.0" × 0.6"), but it is also slimmer since it does not have a USB connector. The ATmega328PB used on the A-Star 328PB Micro boards has some debugging features that are not available on the ATmega32U4. You can find more details in the ATmega328PB datasheet, which you can find under the “Resources” tab of the A-Star 328PB Micro product page.


Having that JTAG connector sticking up kinda’ ruins the profile of the Mini. :rofl:

I think I’ve figured out the Micro, so I’ll stick with that unless it bites me, thanks.