ChipKit MAX32 – 9×14 LED Matrix – Project Description
This project started a few weeks back when one of my Arduino colleagues brought the LOL Sheild to my attention. (A write-up for the LOL Shield can be found on its designer’s page: jimmieprodgers.com ) This is a very interesting little LED circuit that uses a concept called Charlieplexing. Charlieplexing in a nutshell is a way to multiplex many LEDs with as few digital lines as possible. This method of control is achieved through tri-stating digital lines.
For the LED Matrix circuit you will find all the project files below.
IMPORTANT CORRECTION: It seems in a fit of some sort of dyslexia I made a mistake on the Shield PCB. At LED position 9B I seem to have placed the LED81 instead of LED18. I have corrected all the documents to reflect this change. Please be sure your PCB is REV2 if you had downloaded my files. Sorry about that.
Once plated through, I strapped the board(s) back on the LPKF machine and began cutting.
Once the traces are milled out, I did the usual chemical tinning with Liquid Tin. Liquid Tin can be found at most electronic parts suppliers. Once complete I began the ordeal of soldering all those many many LEDs. My first set, however, was to begin with the 0 Ohm resistors… and yes I actually used 0 Ohm resistors because they were there. They really are not necessary. Wires work just as well. 🙂
Next, I soldered the headers. But, this was a mistake. (I was waiting for my order of LEDs to come from eBay and I got impatient.) The LEDs really should have gone on next because they are shorter than the headers. It was a royal pain soldering the LEDs last.
And then bring on the LEDs. This process took quite a while to complete. But I finished two boards. Hardware completed.
An then…. tragically…. The software:
I was excited to work with my newly created LED Matrix, I downloaded all the appropriate libraries from LOL Shield Arduino Software Library. I had everything installed and ready to go… I hit the upload button to load my sketch to my ChipKit… and error…. not compatible. As it turns out the ChipKit handles a few things differently than the Arduino. Namely the timers and interrupts. So, unfortunately, the LOL Shield Library does not work with the ChipKit. But I am working on it….