Unicorn Hat HD, adjacent pixels lighting up



I recently bought the Unicorn Hat HD and tested it by running the “lines” script.
I noticed some of the pixels under the diagonal green line lit up, which they shouldn’t do.
They aren’t at full brightness, but definitely noticeable.
Running some other test scripts showed the same problem, it always seems to light up the pixels below in the colour of the one above. So if I turn on a single red pixel, the pixel below will show a dimmer red.
It’s most noticeable with green pixels however.

Does anyone know what the problem could be? Is it software or hardware related?



I’ll fire mine up latter on today if I get the chance and run that example and see what I get.
Do you have any standoffs under the Hat to keep it level? If no, make sure the bottom side of the HAT isn’t touching anything on the Pi. Especially if you have a heatsink on your Pi.


Nothing’s touching, and it’s not only the example scripts. Just dawing one pixel in the middle of the matrix causes the one underneath to light up aswell


Pressed down firmly on the GPIO? I have to go find a spare power supply, if I have one? Looks like I took the one I had connected to that Pi for something else?

Took a PS from another project. That Pi is doing updates after a clean boot with a fresh install of Raspbian. I’ll add to this post as I progress, no need to reply to it just yet. ;)

Install is finished. Rebooted and ran line.py. Not seeing what your seeing. Just the one line of pixels being displayed for each line / color.


If it was me, I’d reimage my SD card with a new Raspbian image and run the one line installer again. Then try the examples again. If its the same issue contact Pimoroni via the contact us link on the Shop page. Also put a link to this thread in that e-mail.


I had installed the library manually, but decided to run the bash script now and it seems to have fixed the issue.
Thanks for your time!


Hey, no problem glad its sorted.
It’s been my experience that making a typo is easy. Finding out what that typo did when the command runs anyway, is the hard part. ;)
I’m not saying thats what you did, just that I’ve done it several times. So these days I take the one command line over multiple route when possible. ;) But thats just me.
If I had more Linux skills I’d maybe go the manual route just to see what happens etc. I don’t and it doesn’t make any sense to me anyway so I take the quick one line installer.