On Tue, Dec 20, 2011 at 02:18:10PM +0000, andy pugh wrote: > After finding that my spindle encoder had drifted, and was counting > 686 of the 720 counts, leading to rather unconveninally-pitched > threads, I find myself wondering if it would be sensible for the > encoder function to set a pin to "counts since last index" on every > index event. This could be monitored in HAL to raise a warning. > Or is this a use-case for the "latched" pins which are only partly > explained in the docs. (and which don't exist for Mesa encoders)
The idea is great - but I'm not sure about "counts since last index". You should think bigger. There are lots of ways encoder hardware can detect problems: invalid quadrature transitions, extra or missing counts between indexes, and maybe more. If the encoder hardware knows pulses per rev (which is not the current scale value it knows) it can detect missing index too. A non-emc machine I worked on would detect missing index when homing (it stopped when there should have been one by now) - emc can't do this currently and it will search forever for an index. I think encoder hardware could have extra parameters to configure these detection features (for example, a ppr parameter), and then one or more fault outputs. They are free to do this now; the canonical encoder interface is a minimum recommended feature set. I think I recall hearing that the mesa firmware detects invalid quadrature transitions (often caused by interference) but the hal driver doesn't make that information available. ------------------------------------------------------------------------------ Write once. Port to many. Get the SDK and tools to simplify cross-platform app development. Create new or port existing apps to sell to consumers worldwide. Explore the Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join http://p.sf.net/sfu/intel-appdev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
