Wawa:
25 TPIC chips is a lot of board area and wire length between chips.
The Arduino I/O pins have to drive that.
Signal rise times become a problem at some point, and buffers might be needed.
No practical experience of the exact limitations.
Someone else might have.
Leo..
Maybe if I just made 16 or 32 channel boards and stacked them rather than putting it all on one board. Is there a better way of attacking this ?
It's funny because the simplest part of this project, lighting leds, has turned out to be the most complex ! For me anyway...