Encoder velocity....

[thasatelliteguy]

What does the value "mills" represent?

it's the command(value) of the clock in the atmega.

Is it the time between encoder marks?

No. It is simply the current time. That's why the newtime-oldtime statement,

What PIC are you using?

Does it have internal timers?
If so you could use an interrupt to start the timer at each mark on the encoder and then check the timer on the next interrupt.

This is my question... what is the command for accessing the internal clock? I may be looking in the wrong places but I can't find it anywhere. I see stuff that appears to be timers, and I guess that would work, but can't I just ask the PIC "What time is it now?" Is it not keeping a clock cycle tally from bootup?

or if you don't need your PIC to do something else while waiting for the next mark you could start incrementing a counter variable when you detect the first mark and then stop incrementing on the next mark and see what the value is. Or if the encoder is going to stop dead at the end of travel you could turn off the motor if the count reaches a high enough value to indicate it has stopped or slowed.

If it stops dead it will destroy itself. It has to stop on deceleration before it binds too much.