The Adafruit LED Matrix Backpack is meant to have its LED matrix soldered right to the board, but instead I soldered on female headers that would permit me to plug in either the mini LED matrix for code testing or the large matrix for deployment. Someone will probably be along to tell me I need a resistor here or there or I’m going to blow some chip up—and they’re likely right—but it seems to have worked so far as-is.
To connect my own matrix to the I2C Backpack, I cut down a piece of prototyping board and soldered in the male headers, then connected the 8″ wires from the last row and last column of the matrix to the board.
Adafruit LED Matrix Backpacks -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 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 adorable LED matrix backpacks come in.
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Thanks for sharing my project!
I know that the MAX7219 you mention needs the current-limiting resistor. Is there something like that on the LED Matrix Backpack that makes it specific to the LED matrix you sell it with? No smoke has been released from Pumpktris yet, but maybe that’s only luck.
Nathan, I noticed your write-up after the Hackaday post and wondered about your resistor question. I believe, without looking at datasheets, that your fine. If you notice, the same 8×8 mini led matrix sold here without the backpack requires the use of individual resistors per pin, whereas with the backpack no resistors are necessary. This leads me to believe that the current is set either in the chip or a single resistor on the backpack. Because most LEDs work within the same amp range you should be fine. But you could compare the amp range on your led with that of what is sold here to be sure.
Having said all that, nice project! Are you planning on opensourcing your code by chance?!
Thanks Dave. After a short break from Pumpktris I plan on cleaning up the code and adding some comments, and then I’ll update the post on my site to include it.