LED Cube: RPi GPIO test and 3x3x3 concept circuit

As already mentioned in my LED Cube intro post one of the milestones on the path to a full-size 8x8x8 cube is a smaller cube for trying out my ideas and testing the fundamental theories on a smaller 3x3x3 cube. Of course on the way to a 3³ cube there are more fundamental issues to solve.

The first issue is to get familiar with using the GPIO pins of the Raspberry Pi, as this will be essential for feeding the driver circuit later with the required animation/multiplexing data. So in the last few nights I've been busy downloading Raspbian, setting up the network connection with my computer (I don't have a HDMI- or Component-capable device available near the work area) and preparing the first GPIO test with LEDs.

It was a good first step which took a couple nights, but after issues with wrong resistors, not-working DHCP from my computer and a wrong connected Pi Cobbler ribbon cable, I could file success with 3 lit and controllable LEDs. These will represent the three channels which I will use later to feed the serial data to the driver IC.

From LED Cube Images

I also began drawing the circuit diagram using the free (for private use) EAGLE PCB Software. I did this to already have a better plan when all the parts arrive and maybe for a much later stage when the cube is ready and I bring the circuit from the breadboard to a custom PCB which is the other main functionality of EAGLE. The handling of EAGLE is a bit difficult, but an excellent (german) tutorial video for EAGLE helped a lot and covered everything I needed to finish the circuit for the 3x3x3 cube.

From Building LED Cube

The next steps on my plan are ordering the final parts, enhancing the circuit drawing for 8x8x8 and beginning to write the LED driving software.

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