Unicorn HD Hat DOA?



I received my Pi3 and Unicorn HD hat on Friday, thank you! But The Unicorn HD seems dead. I can’t get anything out of it. I read from other similar forum posts that there’s supposed to be some sort of white LED pattern showing when power’s applied, even without using the python lib to do your own stuff? Mine refuses to do anything. I’ve made sure it’s firmly seated on the pins, removed & re-installed a couple of times, checked for any small debris in the socket - all fine. I downloaded the software (definitely the HD version, not the non-HD one), and the examples run with no errors, just the expected console messages, but no lights on the Unicorn.

Is there something I can try to check if the Pi is even seeing the Unicorn? Some way to interrogate the SPI bus?

It’s my first Pi and other than the Unicorn HAT not working, everything’s been great!



Oh, I’m using the official Pi power supply in case that makes a difference - part of the Pimoroni P3 B+ Essentials kit. Thanks!


I have a Unicorn Hat HD plugged into a Black Hat hack3r board powered by a Pi Zero W.
No LED’s lighting up on boot up that I could see. Mine is behind the black difusser.
I’m just now running the install script, being a Pi Zero it might take a while.
Once thats done I’m going to reboot and run one of the examples, and get back to you.


Thank you! Great to know I shouldn’t see anything on power up.


I had this all up and running previously. I just redid that Micro SD card with the latest Raspbian so I’m starting from scratch. Just did the reboot and no LEDs lit up. Just ran demo.py and its running Ok. I wanted to verify that the latest Raspbian didn’t break something, it happens some times.
I don’t know how you check SPI? My Linux skills are pretty basic to be honest.


Official Pi foundation power supply here too. If it was a power issue you should see a lightning bolt flash on your monitor, indicating and under volt condition. Overcurrent usually results in an under volt condition on the power supply. My Unicorn Hat HD will eventually end up on a 3A+. Just don’t have one not already in use.


Are you running NOOBs or straight up Raspbian? I ask because NOOBs can cause issues with “some” installers. The file structure and folder layout is slightly different.


I’m using the NOOBS raspbian distribution that came with the Essentials kit. Is there another distribution I should try? You can see the SPI interfaces by running ls /dev/spi* at the bash prompt, but I’m not sure how to go from there to seeing what’s attached.


I see two spi devices listed, /dev/spidev0.0 and /dev/spidev0.1


You can get the Raspbian image here,

And us Etcher to transfer it to your Micro SD. I don’t know that NOOBs is your issue, just a hunch that it “might” be an issue.


Cheers, I’ll try that next!


How to put it on your card is here,

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No joy unfortunately - the image flashed fine and the Pi itself works but not the unicorn hd.

I saw on the unicorn hd page it recommends stand-offs - what are these for? Could the bottom of the unicorn hd be touching off something on the Pi that’s shorting it out?



They are used to give a good physical mounting of a hat or pHat to a Pi. They hold it in place and keep it level. I use them on all of my builds. Even test setups. You can’t see them in this picture but they are there between the Unicorn hat and the Black Hat hack3r board. Its what the difusser is screwed into.


Forgot to mention, unless you have a heatsink on the CPU / SOC of the Pi, I don’t think the Unicorn Hat will short out on anything? A piece of cardboard should do in a pinch as a spacer.


Thanks @alphanumeric, I’ll try the piece of cardboard but I’m just grasping at straws at this stage really. Great to have your help!


Yeah its looking like the Unicorn Hat was DOA. They do test them, but things happen. Somebody might have kicked your box during shipping etc. If you go to the main Shop page, there is a "contact us’ link at the bottom. Click that and you can e-mail tech support directly. I’d put a link to this thread in that e-mail then see what they say.


True… of course it could be the Pi3 side either, if the board was damaged/dropped? I’ll email tech support and link back here. Thanks again!


I never thought to ask, do you have another Pi?
If yes just swap that SD card and Unicorn Hat over to it, no real need to reinstall all the software again.


I don’t, unfortunately - this is my first one!