Tom Easterday wrote: > Thanks Jeff and Stephen. We were thinking of using it for home. So, if the > index pulse is going to be different each time, then how do physical limit > switches work any better? It is a digital input, no? > > Also, Jeff mentioned moving at a snails pace...we will be moving slowly > during homing. We would get near home, find index pulse while moving > slowly... > When using hardware encoder counters, the position count in the hardware is reset when the index pulse is seen. This operation is performed at whatever update rate the encoder counter runs at, it is 1 or 2.5 MHz on the Pico Systems boards (depending on model and firmware version). If you were to do the final homing stage slow enough that you were only moving at 1 encoder count per servo period, then you at least have a chance to detect the index pulse. Many encoders have an index that is about one cycle wide, ie. 4 quadrature counts. But, some gate the index with the A signal, for instance, reducing the width to the same as one count. If your encoders have a full-cycle index, you should be able to detect it pretty easily with slow movement. If it is the smaller version, then you may need a latching scheme to assure you detect it every time.
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