To make a long story short, I ended up at one point, buying two little 3x3x3 LED cubes from Radio Shack. They were about $20 a piece. Ultimately, the point was to mount them on my Udoo Quads (http://www.udoo.org) and control them through the Serial comms port using a Python script. While I had some trouble porting over the code from the Arduino it was meant to run on, once I figured out what I was missing it was a snap.
I even asked Dave to look at it, he couldn’t figure it out either, the answer came to me in a flash of insight. The cube is a Charlieplex system, and I was confused about the order in which the pins controlling the LEDs were being set high and low. To both of us at the time, it made sense, setting them high, turns the LED’s on, setting the pins low would turn them off.
Turns out it was the opposite. What we both missed was that, when the pins are low, they are grounded. Thus, if you are putting in 5v at each end, you get nothing, ground the cathode end and the power flows…. and we both missed that part, that the cathode was set high to “shut off” the LED’s.
Anyhow, I kept one of the cubes for other purposes. I wanted a cube in a different color so I sourced almost all the parts from eBay and assembled one from scratch in Blue 3mm LEDs with an Arduino prototyping shield. See the video below for the Cubes in action.
Aside from having a cool little 3x3x3 LED cube, I had a purpose for controlling them with the Udoo’s. At the moment, I use the Udoo’s mostly for experiments, while they are not doing anything in particular, they are running Litecoin crypto coin mining software. They really aren’t powerful enough to make any Litecoin worth having, BUT, when the mining software submits a hash, it takes the cube out of demo mode (cycling through all the patterns it has except for one special one) and then display’s the special one. Basically when a hash is submitted, the cube pulses itself.
The two Udoo’s the cubes are on, will never find a block or get much in the way of work hashes, but it is a neat conversation piece.