3 weeks ago

Unicorn HAT HD review

Create brighter projects with the new Unicorn HAT HD

The Pimoroni pirates have upped their game with this new HD version of the classic Unicorn HAT, featuring a 16×16 array of super-bright LEDs. Boasting four times the number of RGB pixels of the original display, it can do a lot more and has a real wow factor.

The full article can be found in The MagPi 60 and was written by Phil King.

The board comes pre-assembled with its female GPIO header, so there’s no soldering required. All you need to do is attach the diffuser layer to the top of the LED array using the supplied nuts and bolts. The diffuser makes a big difference to the visual effect, filling out the gaps in the display between the rather small pixels.

Communicating with the Raspberry Pi via SPI, the HAT uses only four GPIO pins (plus power and ground). Best of all, it has its own ARM STM32F chip to do all the heavy lifting, acting as a middleman between the Pi and the three LED drivers. This means there’s no lag at all when you send data to it, as demonstrated by the camera program downloaded with the one-line software installer.

The camera demo displays the low-res live view from the Camera Module (although it was tricky to connect the latter to the CSI port on a non-Zero Pi model with the HAT sitting on top).

Other example programmes also showcase the Unicorn HAT HD well, particularly the snazzy shading demo which transitions between four classic graphics effects to produce some awesome eye candy. A Snake game and Conway’s Game of Life demo really benefit from the increased number of pixels, confirming how much more versatile this display is compared with an 8×8 version.

There’s even a version of Unicorn Paint that you interact with via a remote web browser, your painted pixels appearing almost instantly on the HAT.

The Unicorn HAT HD has its own Python library, including functions to set the brightness and rotation. Scrolling text across the display isn’t as easy as using a single function, requiring a fairly complex loop, but you could adapt either of the impressive multicoloured text demos for this purpose.

Last word


The increased number of pixels means the Unicorn HAT HD is a more versatile display than its predecessor. The performance is excellent, too, as it reacts near instantaneously to whatever data you throw at it. Since the HAT’s ARM chip does all the processing, it’s even technically possible to drive multiple displays from one Pi.