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Originally Posted by Uberbots
im pretty sure that this is a fairly simple topic... but i cant figure it out.
What i am looking at is Kevin's encoder code and trying to determine the interrupt routines i would need to measure a pulse width from the Gear Tooth Sensor. This is kind of important because i need to know direction, and looking at the specs for the GTS i can see that a CW tick has a pulse width of 45 us, and CCW has 90 us.
I know how i would detect a tick, but how would i detect the pulse width?
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Well, I have good news and I have bad news. Being a glass half-full kinda guy, good news first: I wrote some code last year to do exactly what you describe. Here's a link:
http://kevin.org/frc/gts.zip. The bad news is that capturing both edges of the shorter pulse is pretty hard considering the amount of interrupt latency involved. I suspect that you could modify the code to infer that the shorter pulse occured, you just won't be able to measure it.
Quote:
Originally Posted by Uberbots
EDIT: some new realizations by me tell me that the PWM pins can be configured as inputs for measuring signals like this...
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Yeah, CCP capture mode would work well, but unfortuanetly the FRC robot controller has non-defeatable output buffers on those pins. If you have a EDU-RC around, PWM 1 through 4 can be configured as an input and map to CCP pins.
-Kevin