On Mon, 9 Apr 2012, Charles Steinkuehler wrote: > Date: Mon, 09 Apr 2012 18:21:12 -0500 > From: Charles Steinkuehler <char...@steinkuehler.net> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: [Emc-users] Parallel Ports, EPP, and Mesa 7I43 > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > I'm new to LinuxCNC and have a few questions about hardware, and want > to make sure I'm understanding things correctly before I start hacking. > > It seems many folks are using a standard parallel port and driving > step/dir signals (maybe even reading encoder pulses?). All well and > good, but limited by the speed of the "fast thread" in terms of pulse > frequency that can be generated (50 KHz is mentioned in the wiki). > > Enter something like the Mesa 7I43, which ties to the parallel port, > but in EPP mode, and supports hardware generation of step/dir, PWM, > encoder support, and much more. This seems like a great thing, but > the comments in the HAL setup for a 7I43 indicate: > > <quote "configs/hm2-stepper/7i43-small.ini"> > # Step timing is 40 us steplen + 40 us stepspace > # That gives 80 us step period = 12.5 KHz step freq > # > # Bah, even software stepping can handle that, hm2 doesnt buy you much > with > # such slow steppers. > # > </quote> > > Questions: > > 1) Why is the step rate so low on the 7I43? I don't see any direct > reason in the hm2 HDL design, the LinuxCNC software, or the EPP port > limitations that should require this low step rate. What am I missing?
Because the example file is a real example file for a specific step drive that just happens to have those timings The actual hardware limitation on steprate is ClockLow/4 (for a 7I43 this is 50 MHz/4 = 12.5 MHz) > > 2) Has anyone tried an intermediate solution between a plain parallel > port and an FPGA hardware solution? I'm thinking about something like > a cheap micro-controller programmed to talk to the EPP port and use > it's built-in timers for step pulse generation (ie: take an Arduino or > similar like folks are driving RepRaps with, and use it as a pulse > generator for LinuxCNC). > > - -- > Charles Steinkuehler > char...@steinkuehler.net > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.11 (MingW32) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iEYEARECAAYFAk+DbugACgkQLywbqEHdNFxW7wCgypr9qnz9NpbrxDf/MkDovbwA > Fa0AoMdTD9mQNNJZQmOpg968WJwG0H68 > =ynHY > -----END PGP SIGNATURE----- > > ------------------------------------------------------------------------------ > For Developers, A Lot Can Happen In A Second. > Boundary is the first to Know...and Tell You. > Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! > http://p.sf.net/sfu/Boundary-d2dvs2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
