Kirk Wallace wrote: > On Wed, 2010-12-01 at 08:44 -0800, Kirk Wallace wrote: > >> On Wed, 2010-12-01 at 12:03 +0000, andy pugh wrote: >> >>> On 1 December 2010 06:26, Jon Elson<el...@pico-systems.com> wrote: >>> >>> >>>> The problem with anding home and index is then the home >>>> signal becomes a VERY narrow pulse, >>>> >> How about using a flip-flop or latch chip? They are cheap and fast, but >> would need to have EMC2 do a reset. A $3 ATtiny (with hardware interrupt >> pin) might work too. But I haven't thought these through yet. >> > A little more thought: > http://www.wallacecompany.com/machine_shop/EMC2/parport_index.svg > > This is a little more complicated than I thought. > Heh.
And to add to the complications, you don't know where you'll get the rising edge once the axis has tripped the limit switch. Since each rising edge of the index mark causes a toggle on the flip-flop, a reversal within the index mark will cause the rising edge of the output to be synched to a different index edge. You can't use both edges of the index mark to toggle, or you're just passing the index through. What you really want is an edge detector that's controlled by the home switch. When the switch output is 0, the output of the detector is 0. When the home switch is 1, the next rising edge of the encoder will set the detector output high until the home switch goes back to 0. This would effectively delay the switch output until an index is seen, but would leave the home switch output high until the switch is no longer active, which is a requirement of a home switch. I haven't written out the actual logic, but I could sure do it with an AVR :) - Steve ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
