On Thu, 28 Apr 2011, andy pugh wrote: > Date: Thu, 28 Apr 2011 23:29:26 +0100 > From: andy pugh <bodge...@gmail.com> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > To: EMC developers <emc-developers@lists.sourceforge.net> > Subject: Re: [Emc-developers] [PATCH] Add support for Hostmot2 Buffered SPI > and the Mesa 7i65 > > On 28 April 2011 23:24, Peter C. Wallace <p...@mesanet.com> wrote: > >> Yes, you must send to receive with SPI so unless you want to duplicate the >> sending (Looking at the 7I43 timing I would think not) you need to reverse >> the >> normal order of read write (for SPI only). This means that the read data is >> always from the last thread invocations write, that is the read data is one >> thread time late. This is fine for the 7I65 as the SPI input data is not >> motion related. > > Ah, yes, I had forgotten that. > Though I guess if somebody tried to use the analogue inputs to read > tacho data to close a velocity loop they might have problems.
Well say you have a 1 KHz servo thread rate. One way of looking at this is that on the average, looking at high speed events, you are .5 mS late, If your data is always an additional 1 mS late you are now an average of 1.5 mS late. So bumping up the servo thread rate to 3 KHz gets you back where you started. (.5 ms average lateness = .333 mS for one servo period + 166 usec average sampling delay) (3KHz and 7I65 not suggested for 7I43 however) > > > -- > atp > "Torque wrenches are for the obedience of fools and the guidance of wise men" > > ------------------------------------------------------------------------------ > WhatsUp Gold - Download Free Network Management Software > The most intuitive, comprehensive, and cost-effective network > management toolset available today. Delivers lowest initial > acquisition cost and overall TCO of any competing solution. > http://p.sf.net/sfu/whatsupgold-sd > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
