What’s better than a single LED? Lots of LEDs! A fun way to make a small display is to use an 8×8 matrix or a 4-digit 7-segment display. Matrices like these are ‘multiplexed’ – so to control all the seven-segment LEDs you need 14 pins. That’s a lot of pins, and there are driver chips like the MAX7219 that can control a matrix for you but there’s a lot of wiring to set up and they take up a ton of space. Here at Adafruit, we feel your pain! After all, wouldn’t it be awesome if you could control a matrix without tons of wiring? That’s where these adorable LED matrix backpacks come in. We have them in two flavours – a mini 8×8 and a 4-digit 0.56″ 7-segment. They work perfectly with the matrices we stock in the shop and make adding a bright little display trivial.

The matrices use a driver chip that does all the heavy lifting for you: They have a built-in clock so they multiplex the display. They use constant-current drivers for ultra-bright, consistent colour (the images above are photographed at the dimmest setting to avoid overloading our camera!), and 1/16 step display dimming, all via a simple I2C interface. The backpacks come with address-selection jumpers so you can connect up to four mini 8×8’s or eight 7-segments (or a combination, such as four mini 8×8’s and four 7-segments, etc) on a single I2C bus.

The product kit comes with:

• A fully tested and assembled LED backpack
• Ultra-bright 4-digit 0.56″ tall white seven-segment display
• 4-pin header

A bit of soldering is required to attach the matrix onto the backpack but it’s very easy to do and only takes about 5 minutes.

To get you going fast, we have revised this popular board to be the same size and pinout as before but now with two STEMMA QT connectors on either side that are compatible with the SparkFun Qwiic I2C connectors. This allows you to make solderless connections between your development board and the HT16K33 or to chain it with a wide range of other sensors and accessories using a compatible cable.

Of course, in classic Adafruit fashion, we also have a detailed tutorial showing you how to solder, wire and control the display. We even wrote a very nice library for the backpacks so you can get running in under half an hour, displaying images on the matrix or numbers on the 7-segment. If you’ve been eyeing matrix displays but hesitated because of the complexity, this is the solution you’ve been looking for!

Note: Cable and board are NOT included

Revision History

• As of June 12, 2024 – This PCB has been revised to include two vertical-mount STEMMA QT connectors so that the board can be plug-and-play with STEMMA QT cables and devices!

Specifications

This board/chip uses I2C 7-bit address between 0x70-0x77, selectable with jumpers

• Backpack Dimensions: 50.0mm x 26.7mm x 6.0mm
• Backpack Weight: 5.6g
• 7-Segment Display Dimensions: 19mm x 50mm x 14mm
• 7-Segment Display Weight: 8.4g

Resources

• Product Tutorial