"wouldnt turning on group 1 section 1 turn on that whole section? not individual LEDs?"Only if the anodes were driven high for all LEDs. Otherwise, just the LEDs with High anodes turn on.The idea is you enable 1 group of 5 LEDs at a time, a 5x5x5 cube would have 25 groups to cycle thru. 4% duty cycle.Driving each group for 1667microseconds would yield a 24 Hz refresh rate - leaving over 25,000 cyckes in between writes to do other stuff.I would imagine a loop within a loop to cycle thru the groups & layers, reading from a 25-byte array (upper 3 bits ignored) to send out a new byte every 1667uS. 2nd array of 5 keeps track of group enable pins, 3rd array of 5 keeps track of layer enable pins.There are 5 anode drive pins, 5 group select pins, 5 layer select pinsl, so the whole cube is multiplexe with just 15 pins, directly controllable by a single '328P chip with no extra shift registers. Just 15 resistors and 20 transistors.I didn't make one myself, just helped the original requestor with a design that could be done.
You can drive the anode with 5 arduino pins. PNP transistors are not needed.