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Old 09-17-2014, 07:53 PM   #1119 (permalink)
e*clipse
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Thanks for the tip - it might be the cleanest solution. I'll look into the attiny this eve.
This kind-of raises a question:
The QEI interface has 3 inputs - quadA, quadB, and an "index" I can see the importance of "index" for an incremental encoder: Without an "index" there is no real place to start counting.

If you have a 2 sine-waves per motor revolution and a complementary 2 cosine-waves per revolution, how critical is the "index"?

It seems to me, at worst you would be off by 180 degrees, and that should be pretty easy to detect.

The implications of this are there would be no need for the "index" pin; it could be used for something else. Also, since a zero (or 0, 180) position are absolute with the resolver, then I really don't need to tie to the microcontroller's pulsing **at all**. This would make the whole external pulse generator easy AND I wouldn't need to isolate the pulses - like using the transformers, etc.

Thoughts?

On another note, I really need to look into the sources of those noise pulses closer. For example, I'm doing all this on a solderless breadboard. These are known to be the worst noisiest option out there. Simply using a proper PC board with a ground plane and well designed circuitry could get rid of most of the other spikes. I would like to use through hole components so anyone could assemble them, but surface mount components do have EMI advantages. I've soldered a lot of surface-mount components in my toaster oven.

- E*clipse

P.S. - e-mail coming

Quote:
Originally Posted by MPaulHolmes View Post
It might be possible. I'd have to check the "NOP" graininess to see what sort of resolution the output square frequency can be. If it doesn't work out, you could add an attiny on your board for $1, and include a crystal, to bump the frequency to 16MHz, which would give a lot more resolution for possible square wave frequencies at 50% duty.
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