-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 7/20/2012 8:28 PM, Jon Elson wrote: > No, the problem is you need to COUNT your pulses. There is no way > for the CPU to know exactly when a pulse gets issued without > counting them, due to slight variations in timing. Now, on the ARM > chips with everything in one, and all clocked off the same crystal, > it MAY be possible to keep some kind of sync on the whole system, > but it might take some revision of the way LinuxCNC works. If the > rates are not perfectly synched between the pulse generator and the > software, small errors could accumulate to cause large position > errors.
My understanding is that one of the first things the servo thread does when it wakes up is poll for the current position from the appropriate lower-level (software step generator, mesa hardware, or whatnot). So assuming the servo thread can actually read the number of counts generated (by whatever means), there should be no position error accumulation. It shouldn't matter _how_ the pulses are generated, as long as there is something (pulse count, encoder position) feeding back to the servo thread so it knows what the position is *RIGHT NOW* and can act accordingly. Is this mistaken? - -- Charles Steinkuehler [email protected] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlAKChkACgkQLywbqEHdNFx5SwCgz3KvZxsX7QO8FLQzfrowFVrF m3MAniIGw1EctzYigz1HY8nOXErg3pWF =lmyF -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
