On Wednesday 09 September 2020 12:38:43 Jon Elson wrote: > On 09/09/2020 11:08 AM, Gene Heskett wrote: > > Is it possible to get an enable signal, per axis, from the mesa > > cards that would become true, hopefully a couple micky-secs ahead of > > the first stepper pulse so no missed steps would normally occur, > > losing its home, and go back false when the last step has been sent? > > It maybe could be timed right if it actually steps on the trailing > > edge of the pulse, and the enabling action was on the leading edge. > > This is the TRICKY bit, knowing when an axis is SOON going > to start moving. > > Jon
I'd be surprised if these things needed any lead time at all, Jon. The hitachi docs on this chip do not mention any timing constraints in regard to this. So its likely that it could be brought up to full song with the leading edge of the pulse. If that triggered a retriggerable oneshot that was then or'd with the pulse, and its output would be the enable high current signal. Let the oneshot time out in 50 millisecs if no pulse, putting it back in reduced current at the end of the move. If the oneshot was in the mesa, would be ideal, and divorced from the enable granularity of the 1khz servo thread. That granularity could easily lose enough steps to destroy a home position, something I intend to have with this BS-1 clone. A oneshot in the hal file would be a disaster in that case because of the millisecond+ delay. A oneshot in the cable to the driver would work, but if its in the mesa card, better yet. :) Stay safe and well, Jon. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
