[DMDX] Re: PIO output issue I will be doing quite well by tomorrow midday when I get off a plane  in miami for Edelyns sisters wedding.  Then better still on sunday  when I get off a plane in the dominican republic!  Not doing that well  today in cold WI! Have a nice break. J John J. Curtin, Ph.D. Assistant Professor of Psychology University of Wisconsin 1202 West Johnson St. Madison, WI 53706 Email: jjcurtin@wisc.edu Office: 608-262-0387 Lab: 608-262-5621 Cell: 608-217-6221 Fax: 608-262-4029 ----- Original Message ----- From: "MATHIS,KRISTOPHER IAN"  Date: Thursday, December 16, 2004 2:46 pm Subject: [DMDX] Re: PIO output issue > Hey John, > That's some really cool detective work.  Hope you're doing well. > Ian >  >  > Quoting JOHN J CURTIN : >  > > Hi Jonathan, > > We have had continued infrequent problems using DMDX to send  > triggers> (event codes) with the Computerboards/Measurement  > Computing PIO card > > to > > amplifiers (Neuroscan synamps) that are monitoring participant's > > physiology.  Periodically, triggers recorded by the synamps are > > incorrect.  I've been working with an engineer here and he  > believes he > > has identified the source of the problem.  Here is what he says.... > > > > ;;;;;;;;;;;;;;;;;;; > > New and interesting info about DMDX and SYNAMPS trigger ports. > > > > The 3 erroneous values  out of 1000 received by SYNAMPS are also > > occurring on your systems on the first floor.  I've pretty well > > characterized the behavior, and I think I know what is going on. > > > > It starts with DMDX and the I/O card.  DMDX is writing to port C  one > > nibble at a time, not a whole byte.  First it writes the lower 4  > bits,> then it writes the higher 4 bits, 4 microseconds later. > > > > It appears that the synamps does _not_ watch the > > trigger port continuously and wait for a change and log it.  I  > believe> it samples the trigger port at the same rate that it  > samples the A/D > > converter and when it sees something other than 255 at the sample > > time, it logs it, then waits for it to go back to 255 and starts > > looking again for change - at the sampling rate. > > > > The sampling rate clock is running asynchronously to the trigger  > port> pulses, so every now and then (approx 3 out of 1000) the  > trigger port > > is > > sampled during that 4 us. when half of the byte at port C is  correct > > and the other half is all ones, leading to the bad trigger  > values that > > Jeremy > > is reporting. > > > > Port C has the ability to be written as a complete byte but it  > appears> that either the DMDX author or the card manufacturer  > drivers chose not > > to use it that way.  I would lean towards it being a DMDX problem. > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > > > Is he correct that DMDX writes to  port C in two sets of 4 bits  > rather> than the full byte?  If so, I agree with him that this  > could be the > > source of our trigger problem with the synamps.  In fact, the  > specific> trigger errors are all consistent with his assessment. > > > > If he is correct, is it possible to have new PIO devices that write > > the full byte to Port C rather than two successive nibbles?  I have > > sponsored changes in the past but if needed would be willing to > > sponsor another if you are willing to make such a change. > > > > Thanks John > > > > John J. Curtin, Ph.D. > > Assistant Professor of Psychology > > University of Wisconsin > > 1202 West Johnson St. > > Madison, WI 53706 > > > > Email: jjcurtin@wisc.edu > > Office: 608-262-0387 > > Lab: 608-262-5621 > > Cell: 608-217-6221 > > Fax: 608-262-4029 > >  ==================================================================== > >    Send mail to DMDX-request@psy1.psych.arizona.edu with the word > >   'unsubscribe' by itself with no quotes in the body of the email > >   to be removed from the list.  The list archive is available here: > >           http://psy1.psych.arizona.edu/cgi-bin/DMDX/thread > >  ==================================================================== > > >  >  > ==================================================================== >   Send mail to DMDX-request@psy1.psych.arizona.edu with the word >  'unsubscribe' by itself with no quotes in the body of the email >  to be removed from the list.  The list archive is available here: >          http://psy1.psych.arizona.edu/cgi-bin/DMDX/thread > ==================================================================== >