What's better than a single LED? Lots of LEDs! A fun way to make a small display is to use an 8 x 8 matrix or a 4-digit 7-segment display. Matrices like these are 'multiplexed' - so to control 64 LEDs you need 16 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 lovely LED matrix backpacks come in. We have them in three flavours - a mini 0.7" 8 x 8, a small 1.2" 8 x 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. These 1.2" matrix backpacks come with three address-selection jumpers so you can connect up to eight 1.2" 8 x 8's together (or a combination, such as four 1.2" 8 x 8's and four 7-segments, etc) on a single I2C bus.
The product kit comes with:
A fully tested and assembled 1.2" LED backpack
Ultra-bright 1.2" 8x8 white matrix
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.
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 eying matrix displays but hesitated because of the complexity, this is the solution you've been looking for!
This board/chip uses I2C 7-bit addresses between 0x70-0x77, selectable with jumpers.
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