External Trigger using NI MIO's PFI0

I am unsuccessfully trying to use external triggering with an NI MIO 
card (PXI-6031E) using PFI0.  This is a suboptimal choice for the 
external trigger input because of the conflict with analog triggering, 
but I'm stuck with it (for now).  Anyway, I've set up my comedi_cmd using...

cmd->start_src = TRIG_EXT;
cmd->start_arg = CR_CHAN(0);
cmd->start_arg |= CR_EDGE;

When I run the program, it never finishes even though I have a nice 1 
PPS pulse going into the PFI0 input.  If I leave out the CR_EDGE flag, 
it triggers right away.  If I add a CR_INVERT flag it never triggers. 
It seems like my 1 PPS signal is not getting through to the chip and the 
trigger detection logic is just seeing a constant level.  I'm going to 
reverify my connections again, but has anyone ever gotten PFI0 external 
triggering to work with an NI MIO card and Comedi?

Thanks,
Dave

Received on 2006-07-20Z21:37:39