@Grumpy_Mike I’m really just fooling around, so all I need is “much faster than the Arduino”; so perhaps I don’t need a non-integral relationship.
That question really deserves its own posting in the forum so other people can chime in. But let me summarize here and maybe repost later…
- 5 to 3 volt converter (I thought to use a 5V tolerant CPLD)
- IO multiplexer/demultiplexer (of course, the new MEGA on the 1280 has a lot of IOs…)
- Interrupt multiplexer
Then there is basic logic that can be implemented in the CPLD. This logic could also be implemented in the AVR of course, but some of them are more efficiently done in a non-Von Neumann hardware architecture.
4 Button state sensing debouncing
5 Simple logic around other sensors (IR for example), like filtering false signal.
5 Stepper motor control (LOTS of motors)
6. USB to serial (may not fit)
Then there is some stuff that would benefit from a high clock rate:
7. PWM outputs
8. therefore LED drivers (but not power LEDs)
9. LED matrix controllers > 8x8
10. Video signal driver (I haven’t really looked into it; but without a DAC this might not really work – could you use PWM and an inductor to smooth out the signal?)
Also, I think that it would be great for educational purposes; the combination of Arduino + CPLD is a simple model for a modern CPU + chipset.
But the most important reason is because it will be fun!