Analog Triggering mess on NI PCI-6110

Hi all,

I’m trying to do some convoluted triggering on a NI-6110. This has been 
working to some extent under windows with the NI provided C-lib drivers, 
but doesn’t seem to translate very easy/cleanly into comedi. I’m new to 
working with comedi, and am having to undertake the conversion of some 
of that MSC code to linux/comedi for easier use.

I have a analog channel that I’m sampling my data from, but I’m working 
with 3 different triggers. 1 Analog trigger that is a reference clock, 
that is not constant, therefore I cannot simulate its timing, but it 
averages around 1.5Mhz. Samples must be taken on the high’s of this 
clock pulse. And two ‘digital’ signals that are not really digital, but 
can be interpreted that way. One of these ‘digital’ signals goes high to 
low over some period, of which I only want to sample when it is also 
high. The other ‘digital’ signal stays low and has very quick blips that 
would look like a traditional glitch, these blips would represent the 
start and stop of sampling, they last very briefly. The comedilib 
reference is very brief on its analog triggering section, and I’m not 
100% sure as to how to interact with mixed signals and triggers like these.

Any suggestions on how to properly implement this? I was thinking the 
following, although very unsure about some of the signals.

Insn.insn = INSN_CONFIG;
Insn.subdev = 1; //Analog Input
Insn.chanspec = 0; // Can I assume this is PFI0/TRIG1 on the NI breakoutbox?
Insn.data = data;
Insn.n = 0; // From what I’ve read this has to be 0 when configuring a 
subdevice?

/* This is the point I’m fuzzy on, I don’t really know what’s supposed 
to go in these fields. Section 4.7.5 of the Reference does not help with 
all the details. */

Data[1] = COMEDI_EV_SCAN_BEGIN; // I think this is the signal I want, 
although
//I cant find much on it as far as documentation.
Data[2] = 0 ; // does this reference Channel 0?

/* I’m also confused about data3 and 4
Is data3 the ‘High’ range of the signal? The threshold voltage which the 
analog signal should be considered high? */
Data[3] = ?;
Data[4] = ?;


Thanks for any advice and help, I appreciate your time!

Doug

-- 
==============================
Doug Farley

Safety Critical Systems Branch 
NASA Langley Research Center

< D.L.FARLEY_at_LaRC.NASA.GOV > 
< Phone +1 757 864-8141 >

Received on 2004-11-15Z23:13:16