A lot clearer now. Thank you!
What is the role of those resistors that you have newly added and what would their value be?
Now that I think I'm very close to fully understanding both the TPIC6B595-based solution and the MAX7219-based solution I'm trying to evaluate the advantages and disadvantages of both:
- The TPIC6B595 solution would only require a 2A power supply because the total theoretical current consumption is only 1.28A. The MAX7219-based solution needs at least 8x330 mA (2.64 A), so I'd probably need at least a 3A power supply, which are harder to come by.
- The TPIC6B595 solution has cosiderably more components, it's easier to make a mistake and the software multiplexing must be bulletproof, otherwise it could accidentally turn on all layers, leading to a current consumption of 8x1.28 A. Software multiplexing would of course complicate the code in unnecessary ways, compared to the MAX7219 solution which only needs the bytes to be sent via SPI.
- The MAX7219 solution is expensive, the TPIC6B595 is magnitudes cheaper.
- The MAX7219 solution requires some additional wires to crawl up to all LED planes, making the construction a bit uglier, but I could come around that by putting the wires into two sets of 8 additional columns in the cube (with no LEDs, just wires). MAybe it would look acceptable. The TPIC6B595 solution solves this problem in a natural way by allowing the current to travel up the cathodes of the LEDs soldered together in 64 distinct columns.
- The MAX7219 solution would make it easier to solder the LEDs together because the 8 distinct levels (planes) would need no contact. I could just add some non-conducting sticks in the end among these 8 distinct planes to make the structure more robust. For the TPIC6B595 solution, on the other hand, it's needed to solder all the LEDs together (cathodes to cathodes in 64 unconnected columns and anodes to anodes in 8 unconnected planes). Makes the soldering trickier.
Are there any other pros/cons for these two solutions that I don't see?
Thank you!
Andras