Here’s an LED and Button shield for the Stellaris Launchpad (translated) which you can fabricate at home. It gives you access to a 5×5 matrix of LEDs, and adds four more buttons. In order to cut down on the number of I/O pins required to operate the lights [Cosimo] is using the concept of Charlieplexing. This lets him get away with just six driver pins and four button pins.
It’s not just the finished product that interests us here. The fabrication itself is worth clicking through to his project post. What initially caught our eye is the use of Kapton tape as an insulator so that clipped off LEDs could be used as jumpers flat against the top side of the board before populating the LEDs themselves. After those are soldered in place he masks them off, as well as the button footprints, and uses spray paint to protect the top side of the board. The final look is more polished than most at-home project boards.
I don’t know… I think it looked better before the spray paint
I agree.
I wonder if you could achieve a good look by putting the ground plane on the top and the signal layer on the bottom?
Yeah, I don’t know. Do you really need a Cortex M4F to drive a few LEDs? What are you going to do with it?
I would be more interested in application that actually use the power of the stellaris launchpad.
Exquisite work – not very manufacturable though. Would be too fiddly to make a thousand of these.
You can charlieplex buttons too.
The idea of a charlieplex of the buttons isn’t bad; I was thinking about this, but with only four buttons I haven’t found it necessary. You can enable or disable it.
I’m agree, “not very manufacturable though”, but this is the difference between “industrial manufacturing” and “craft manufacturing”. For me is its advantage… ;)