SPI working in a 18F452 but not in a 18F4520

We've all been there - you've spent hours and hours trying to get that sketch working, but somehow, you're not reacting well to time critical events in your system. Maybe it's a wireless peripheral indicating when a packet is ready. Maybe it's an external Flash device signaling when data is ready to be read out. Maybe it's as simple as a button push that you need to react quickly to! But, try as you might, it seems the best way to see these sort of events is to just `digitalRead()` that pin over and over in your main `loop()` function until something interesting happens. ...or is it?

Graphene, a sheet of carbon atoms that is only one atom thick, could change the future of electronics. It's much more energy efficient than silicon and dissipates heat faster as well. There's evidence that graphene works even better when it's combined with other polymers, too, making its potential applications innumerable.

This is one simple way to control a LED, fan, relay or solenoid with a computer and a PIC.