On Sat, 2008-08-09 at 13:17 -0400, John Kasunich wrote: ... snip > Mostly something like the arrangement Kirk Wallace has - software > stepping, using the GPIO for the step pulses. You might ask "why do > software stepping when there is hardware stepping available?" In many > cases that is a darned good question, but in Kirk's case, I don't think > the existing firmwares supported hardware stepping. > > There is also the case where you need one more channel of stepping, or > encoder counting, or whatever, and you don't necessarily need the full > hardware performance. For example, the Mazak at the CNC workshop uses a > 4-channel Motenc board. Three encoder channels are used for X, Y, and > Z, and the fourth is used to count the spindle encoder for spindle > orient and rigid tapping. We used a software encoder counter and two > GPIO pins for the jogwheel, since it doesn't spin fast enough to require > hardware counting. ... snip
Most of this thread is Greek to me, but my Shizuoka is my only stepper machine. I set it up with parallel port software encoder decoders and stepping because I could do it 'quick and dirty' without spending any money, plus I needed quadrature stepping output. It turned out that this setup drove the steppers (half-stepping) to their highest speed before stalling, with some to spare, so there isn't much incentive to use additional hardware. The plan is to go to servos in the future. A little off topic, because at a given step rate the A and B frequency is half the step rate, I was thinking that the quadrature output would double the effective max stepping rate. The more I think about this though, that is only true if the hardware pin frequency is the limiting factor. The stepping rate is limited by the max base-thread rate and will be the same no matter the form the output takes? After I got the Shizuoka set up, I got a Pluto-P. It doesn't output quadrature steps, but step/dir is easy to convert to quadrature isn't it? -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) ------------------------------------------------------------------------- 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
