Roland Jollivet wrote: > 2008/8/6 Jeff Epler <[EMAIL PROTECTED]> > >> To accurately read a quadrature signal you must sample it frequently >> enough that there is absolutely never more than one input transition per >> sample............. > > > Hi > Why aren't simple set-reset latches used? with interrupt on change? Then you > only need to act when something happens, instead of spending a lot of time > checking to see if it might happen, and you'll never miss a change, ever. > Add another simple circuit that will monitor > -another-trigger-before-latch-cleared-, and you will immediately be alterted > that the PC was not fast and missed a pulse. > > Maybe it's the style of the algorithims that make this difficult? > > Regards > Roland
The whole point of software counting encoders is to do it in software. If you are going to add hardware like set-reset latches, you might as well add counters and get much better performance. Interrupts also get complicated when you consider that you will probably want several encoder channels. You can determine the maximum interrupt rate from a single encoder if you know the top speed and counts per rev. But as soon as you get multiple axes, you can have counts happening on multiple channels at the same time, which means multiple interrupts spaced extremely close together. It's only my opinion, but I'm convinced that multiple axis encoder counting, multiple axis step pulse generation, and multiple axis PWM generation are better done by a fixed rate "clock" rather than by interrupts. The algorithms used in hardware counting, step generation, etc are pretty much exactly the same as those used in software - the only difference is that hardware can process channels in parallel, can therefore be clocked several orders of magnitude faster. Regards, John Kasunich ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
