Unexpected results from Encoder::GetRate()

[Alan Anderson]

Originally Posted by vamfun

The scheme that I'm describing is a valid quadrature decoder in that it uses the B channel to determine direction.

No, it's just a counter with a direction input. It happens to work with a quadrature encoder if you don't have "noisy" rotation. If the encoder happens to oscillate a bit back and forth at the A channel transition, you'll get false counts.

That exact situation happened on our "Triple Play" robot. We had quadrature encoders on miniature omniwheel-ish rollers to track our motion on the carpet. We could watch the wheels not spin appreciably while the code told us they were making several revolutions. I fixed it by implementing a true quadrature decoder. Something almost exactly like my code was independently developed by Kevin Watson and incorporated into his Encoder.c library for the IFI controller.