CHIPKIT MAX 32 – LED Matrix Shield
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 it’s designer’s page: jimmieprodgers.com ) This is a very interesting little LED circuit that uses a concept called Charlieplexing. Charlieplexing in a nut shell 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.
There wasn’t a shield available for the MAX32, so I designed one based on the Jimmie Rodgers’ LOL shield. The shield is an array of red LEDs in a 9 x 14 “pixel” grid. I have seen a number of cool projects on the web that use a similar shield. One of which is a Pong Game (an example program included with the Arduino Library). Some other uses might be, scrolling text, simple animations, or as a graphical display.
This design is in the public domain. For this design I have tried to follow the Open Source Hardware protocols outlined by OSHWA (Open Source Hardware Association).
(OSHA Quick Referance) (OSHW Statement of Principles and Definition v1.0)
PROJECT FILES:
For the LED Matrix circuit you will find all the project files below.
ChipKIT Max32 – LED Matrix Shield Files
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.
Hardware:
So, after using the Arduino LOL Shield as a reference design, I have laid out a PCB and begun milling. I have access to a x-y LPKF milling machine to make my prototypes. This board was a little more complicated than most of my designs, so I had to through with hole plating. The disadvantage of milling prototypes is that through hole plating is not available. In my case I also have access to a through hole plater. My board is a panel of 2 PCBs in this case.
CHIPKIT MAX 32 – LED Matrix Shield PCB after drilling & Plating
Once plated through, I strapped the board(s) back on the LPKF machine and began cutting.
CHIPKIT MAX 32 – LED Matrix Shield Milling PCB traces
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 begun 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. 
CHIPKIT MAX 32 – LED Matrix Shield Soldering Components
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.
CHIPKIT MAX 32 – LED Matrix Shield Soldering Components
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.
If you have gotten this to go OR have taken this as a challenge please let me know what you have found out!
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