On Thu, 16 Jul 2009, Leslie Newell wrote: > Date: Thu, 16 Jul 2009 22:33:13 +0100 > From: Leslie Newell <les.new...@fastmail.co.uk> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Hostmot2 homing > > Hi Peter, > > I have been doing some more tests on this. Playing around with filters > and screening had no noticeable effect. However I have hit an odd > anomaly. Just out of interest I switched the 7I29 to single ended input > and suddenly it is rock solid. So it can't be noise pickup in the > cabling. Any ideas why differential inputs are causing a problem? I know > both index and \index are connected correctly.
One difference is that the TTL inputs have an RC filter, the differential inputs have none. I wonder if your index outputs can drive the termination resistor. Have you measured you index and /index outputs for reasonable differential output voltage when terminated by the 7I29? Also are you sure about the jumpering: differntal mode is selectec with jumper W1 or W4 moved so its closer to the encoder 10 pin header > > Another odd thing - in differential mode if I disconnect one line the > input toggles randomly, obviously picking up noise. Again, shouldn't a > balanced input give no output with one line disconnected? Im not sure there are any guarantees of what will happen if one input is connected to a possibly noisy input line and the other is open. I would not expect any outputs signal as I would expect the termination resistor to make the open input follow the noise driven input. > By the way, is the 7i29 encoder circuitry the same as the 7i33? Yes, and we've pretty much had 0 trouble with it. > > Les > > > >> >> The hardware works (just tested SV12 encoder 5). There may not be much >> apparent difference between inverted or non-inverted index because they are >> both edge triggered. It looks like the driver does not set the ABGateIndex >> bit >> so what I said about index happening all the time with the wrong index >> polarity would not happen, just the home position might change by a count or >> 2 >> depending in index width (assuming a normal rotary encoder short index). >> >> If swapping the leads solves your problem, it might be electrical >> troubles. The current driver not setting ABGateindex means a narrow index >> pulse would work regardless of polarity though the home position would >> change slightly depending on whether the rising or falling edge generates >> the index event (since an edge is always needed) >> > > ------------------------------------------------------------------------------ > Enter the BlackBerry Developer Challenge > This is your chance to win up to $100,000 in prizes! For a limited time, > vendors submitting new applications to BlackBerry App World(TM) will have > the opportunity to enter the BlackBerry Developer Challenge. See full prize > details at: http://p.sf.net/sfu/Challenge > _______________________________________________ > 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. ------------------------------------------------------------------------------ Enter the BlackBerry Developer Challenge This is your chance to win up to $100,000 in prizes! For a limited time, vendors submitting new applications to BlackBerry App World(TM) will have the opportunity to enter the BlackBerry Developer Challenge. See full prize details at: http://p.sf.net/sfu/Challenge _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
