<div dir="ltr"><div>Hi Christina,</div><div><br></div><div>For historical and technical reasons, ACK pin 10 of the printer port is often used for handling trigger signals. One of the reasons is that this input can be handled by so called interrupt routines, which offer a very efficient, reliable and fast method for handling even the shortest trigger pulses. (Interrupts are edge-triggered!) However, EPrime uses a polling technique to detect bit-changes on a specified input port or status register. When a trigger signal is not always detected by E-Prime, it could be the case that the trigger signal is just too short to be detected reliably. For example, if the port is checked every millisecond, a pulse with a duration of just 0.5 milliseconds has a change of about 50% to be detected. The trigger option of Philips MR systems generate TTL-pulses of only a few microseconds, so polling won't work in that case. (We use a small piece of hardware that extends the duration of the pulses to about 20 milliseconds to solve this.) Siemens systems use a different strategy: they toggle the status of the digital line at every volume, so the voltage level will change once at every TR.</div>
<div><br></div><div>You also might find the attached test-scripts useful for checking the ACK-line of the printer port. I created these scripts a few years ago when I didn't have proper measuring equipment available, and the are programmed really quick-and-dirty, so don't be mislead by poor programming. I think the default configuration is fine for testing the ACK line, but if you would like to change the IO port address or pin number, you could modify the TriggerMonitor.startupinfo-file, or change the following lines in PortScope.es2:</div>
<div><br></div><div>Case "LPT1, ACK"</div><div><span class="" style="white-space:pre"> </span>IoPort% = &H378 + 1</div><div><span class="" style="white-space:pre"> </span>IoMask% = &H40 ' ACK = pin 10 = bit 6</div>
<div><br></div><div>However, keep in mind that these scripts will also miss very short signal changes.</div><div><br></div><div>Best,<br>Paul</div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">
On 13 May 2014 18:42, <span dir="ltr"><<a href="mailto:andreou.christina@gmail.com" target="_blank">andreou.christina@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hi,<div><br></div><div>does anyone here use E-Prime for fMRI experiments? We are trying to get it to work and even got the EEfMRI Extension, but the RunBegin Package Call simply refuses to recognise the trigger pulse. I tried simply inserting a wait object and define the parallel port as trigger mask (allowable response {ANY}), and it didn't work either. </div>
<div>We did a bit of troubleshooting, and ended up changing the cable connecting the scanner to the PC: the cable we normally use transmits the signal to pin Nr. 10 of the port (acknowledge or interrupt pin), if I understood our technician correctly - this works both with Presentation and Cogent software. However, we saw something on the pstnet support page about E-prime recognising input to pins 2 to 9, so we changed that and used a cable that sends the signal to pin Nr. 9. Now we have a very peculiar situation:</div>
<div><br></div><div>- the trigger pulse is recognised by the wait object, but only sometimes (every 4th, 5th, or 10th pulse is recognised, there does not appear to be a system). When it is registered, it appears as 7 in the E-Dataaid File and in the .pdat file.</div>
<div>- when I substitute the default allowable input (^) to the RunBegin Package Call to 7, it still isn't recognised at all.</div><div><br></div><div>I am in contact with pstnet support, but we haven't come further than that. </div>
<div><br></div><div>Has anybody encountered similar problems when setting up fMRI experiments? Any input about your experience and/or settings you came up with will be valuable!</div><div><br></div><div>Thanks,</div><div>
Christina</div></div><span class="HOEnZb"><font color="#888888">
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