That's ok. I've read up on static variables. Didn't know about that. I have a lot of variables I declare at the beginning (global) but they can actually be static. They are only used in 1 function, but that function needs to remember them. I'm going to move all my globals to static that don't need to be global. I guess this is good practice?
It will make my code neater and easier for me to read.
ps. So this timer thing that's programmed directly in (note my original post). ...It must not interrupt my SPI transmission, or anything else important? It's all working, seemingly.
Here's the code that I really don't know what it does, it's not normal Arduino code...
// Run timer2 interrupt every 15 ms
TCCR2A = 0;
TCCR2B = 1<<CS22 | 1<<CS21 | 1<<CS20;
//Timer2 Overflow Interrupt Enable
TIMSK2 |= 1<<TOIE2;