- From: Bruno Weber <bweber_at_neurol.unizh.ch>
- Date: Sat, 23 Nov 2002 12:38:59 +0100
Dear all, I still have problems with triggering/pretriggering. It would be great if someone could post some code that does it so that I could learn how to do it. many thanks Bruno my last message: I have found this message in the archive: On Mon, Nov 11, 2002 at 03:00:05PM -0500, do_not.email_me_at_nowhere.org wrote: > Hi, > > I am looking at the feasibility of using the DAQ card listed above. > > The signal of intereset is aperiodic <100mS in duration every 5-10 Secs>. > I would like <ideally> to trigger off of the 100mS "blip" and, whith a > combination of pre&posttrigger acquire the whole blip <including onset>. > The card's FIFO <8KB> is large enough to store all of the event. Pretriggering is not supported in Comedi. The main reason is that to do it correctly requires a 3-nested-loop equivalent to the 2-nested-loop comedi_command structure. This is planned for post-1.0 Comedi. It's generally not difficult to emulate pretriggering in software, although with the overhead of an extra analog channel to measure the triggering signal. Now, my question: how would you do the software emulation of pretriggering? My program should be able to acquire one or two channels at about 10kHz, pretrigger time is about 5 ms and posttime about 20 ms, the triggers occur between say 10 - 40 times per second. You say you need an extra analog channel, should the trigger not go to a digital input? I work with a pcmcia card ni6024e. many thanks Bruno -- Bruno Weber, Dr. phil. University Hospital Depts. of Neurology & Nuclear Medicine Frauenklinikstrasse 26 CH-8091 Zurich Tel: ++41 1 255 55 79 Fax: ++41 1 255 44 29
Received on 2002-11-23Z11:38:59