LabVIEW
Rotary Encoder + ni usb 6009
Solved!
I think the OP understands he should be using a counter card, he's not asking what would be best, just how to use his limited resources in this emergency situation.
OP: You can do this but it will be something of a pain. If you need *continuous* positioning it will be a larger pain in the butt, but for "A to B" measurements where you just need to know where it wound up it won't be too hard.
Do some research on quadrature encoding. That will tell you what you need to know about how to interpret the signals. As far as LabVIEW goes, you'll need to just take a measurement at the highest speed you can on the analog channels, then convert manually. As far as I know there isn't any solid reference code on this, as like everyone else said you're using the wrong tool for the job, so you're gonna have to McGuyver it a little to make it do what you want.
Anyway, I think your supply is 5V, so your signals will be 0 or 5 V, with some noise. I'd take a sample set, then start at sample n=0 and work my way forward. If you see one line change state (i.e., it crosses 2.5V in either direction), increment a counter. If the next line changes state, increment it again; if the same line changes state, decrement the counter. Once you understand how quadrature counting works this should make sense. There are a million articles on this so I won't re-explain it here, but that's what you're going to have to do.
This should be pretty straightforward. Use the Example Finder (Help-Find Examples) to get started with analog acquisition, then you'll just have to figure out the code to interpret it. I'd recommend creating a chart of dummy values that you can use to test your decoding logic, that way you don't have to physically spin anything. If you know you should be seeing exactly 300 counts for a given set of quadrature inputs, you can run that sample code through your logic to see if you get 300 counts on the nose.
I agree, I don't think you have fully understood quadrature. You unfortunately will absolutely have to understand it to be able to make this system work given your limitations.
If you're at FF (A and B state) and move to FT, increment. From there, if you move to TT, increment again. From there, if you move to TF, increment again, then FF to increment yet again.
Quadrature encoding uses the following pattern:
FF
FT
TT
TF
FF (repeats)
Going "down" the list should increment your counter. Going "up" the list should decrement your counter. Check every sample state and remember the previous sample state using a shift register and you can count things. Once you have something semi-working, upload your code (save for no later than 2016 if possible, to make sure everyone can see it) and we can try to help you debug.
I think I would start by converting your waveform from analog into digital. Once that plot looks good, then try decoding it. Split up the task at hand into smaller and smaller parts until you can solve each part.
