for smooth operation though i'm not sure if the PI will be up to the task, having it as a master and sending the pattern requests to the Arduino is good. I have not yet seen a PI do this. Not saying it cant be done but to be honest, a PI is not the best choice for hardware control of this nature. An Arduino or similar (MSP430, TivaC etc) is much more adept.
for smooth operation though i'm not sure if the PI will be up to the task, having it as a master and sending the pattern requests to the Arduino is good. I have not yet seen a PI do this. Not saying it cant be done but to be honest, a PI is not the best choice for hardware control of this nature. An Arduino or similar (MSP430, TivaC etc) is much more adept.
If I were doing it I would use an FPGA (which would get rid of the LED driver chips) but that's because I use them all the time so I have all the tools.
You don't necessarily need a driver chip with an arduino. For a 4x4x6 cube I am working on the only io expansion I am using is a single Johnson counter. This is using an arduino Leonardo.
How will you get any power into your LEDs without drivers - you have 96 LEDs (which is a lot less than the 512 for an 8 x 8 x 8) cube but the maximum total current you can put out is less than 200mA which won't be very bright. (Perhaps I'm missing something - can you post a sketch of your ciruit ?)
that's total for the chip too, you are limited also to 20mA per pin, absolute max being 40mA but not recommended and that would also be dropping a lot of volts in the chip
I'd still need some power devices for a big display or abright one but:
The Lattice ECP2 in 208 pin TQFP package can do a maximum average IO current of 146 x 8 = 1168mA on 146 pins. You can't use all the pins for LEDs so over, say, the 96 pins of Samuel's cube it can do 12mA per LED continuous, no multiplexing required.
can the FPGA handle the overall power dissipation, there is always a current per pin but also a total current per silicon chip with most often is not the sum of all or even most of the pins
btw, typical LEDs require 20mA for full intensity, as you are multiplexing the pins (There not on continually ) then this current needs to go up proportionately, so if your at a 50% duty cycle, you need 40mA, 25%=80mA etc
if you don't account for this then the typical result is un even brightness as the number of LEDs change over the pattern or they are quite dim all the time. just look at how a 7segment display works.
yes you can get away with it to a certain extent (Small number of leds ) but it will bite you as your cube grows in size
