Cathode board works!

And we have a video!

Pretty neat! I found a bug in my bit angle modulation code which caused some weird things. After I fixed that everything worked like a charm.
My setup is like this:

• An Arduino Nano on the left side of the breadboard, this microcontroller has a bit of animation code and it streams the resulting led states (on or off for each LED) to the cathode board. It does this roughly 12.000 times per second, creating a very smooth image. It's important to note that it is streaming the data for a full 8x8x8 RGB cube, but only one row of the top level is is shown (since that's the last byte that is streamed). On other words, the same smoothness can be achieved when the complete cube is connected. It's also interesting to note that this code is capable of streaming 100 "frames" per second and has loads of cpu power left.
• The Arduino is connected to my cathode control board using a ribbon cable. Each of the five wires in the cable is connected directly to one of the pins of the shift register on the cathode board for full control. There's a three wire power cable as well; one wire for logic power supply, one for logic ground and a separate one for LED ground. Finally there's an eight wire ribbon cable connected to the cathodes of the LEDs on the breadboard.
• The 8 LEDs on the right side of the breadboard have their anodes connected directly to 5V. The green cathodes go to the cathode control board which contains a series resistor for each LED. The other end of each resistor is connected to the collector of a transistor. The emitter of each transistor is connected to the LED ground pin on the board, and the base goes through a series resistor to an output pin of the shift register. If the output pin goes high, then current can flow through the transistor and the LED goes on. If the output pin is low then current is blocked and the LED goes off.

Next up: two more boards for full RGB control :)