reading a pulse per second signal with pci 1426

[sandeepchinni]

Hi,

I am interfacing a PCI 1426 frame grabber with an external device to receive trigger signals from device to do image capture with the camera connected on the camera link port.

The manual of the device says that it will give out a pulse per second signal with the following features:

PPS Output:

Physical interface: RS-422
Width: 10 microseconds (default); user programmable from 10
microseconds to 500 milliseconds
On-time edge: Rising edge on time (default); user programmable rising or falling

External Event Capture:

Interface: RS-422
Resolution: 488 nanoseconds

The manual of the frame grabber says that Pins 14 and 15 "can be used as independent RS-422 trigger inputs instead of, not in addition to, TTL_TRIG<3..2>."

Does this mean that I can connect the output from the external device to any one of these pins to detect the PPS signal? If so, are there any sample programs in the example which I could use to know how to detect the signal?

Thanks & Regards,
Sandeep

Message Edited by sandeepchinni on 04-08-2009 02:32 PM

[JeffL]

Hi Sandeep,

You should be able to use any of the triggering examples in the LabVIEW Example Finder for IMAQ. The trick to access the RS-in lines on the 1426 is buried in the help for trigger read:

"Note  To use the ISO_IN or RS422_IN signals on the NI PCI-1426, select External as the Trigger Type for your function and choose ISO IN or RS-422 as the Signal Level for the trigger line in Measurement & Automation Explorer (MAX)."

I hope that helps.

[sandeepchinni]

Hi Jeff,

I followed your instructions but I did not get the desired results. Attached is the simple program that I am using and also a screen shot of the settings in MAX. I have connected the signal to pins 7/8 on the frame grabber.

I other point that was mentioned to me was that the port which produces the PPS is a BNC port and hence would have only signal pin (no ground). In such a case shouldnt I be connecting the signal to the any one of the TTL lines since 7/8 are RS-422 line and the source is not a RS-422 source?

One more question, is it possible for me to communicate with the device which has a USB port through the D-SUB 15 pin port? If so, how?

Thanks & Regards,

Sandeep

[Dennis_Knutson]

The question about the usb connection has been asked before here and on LAVA. If you insist on pursuing this, go to www.usb.org, get the specs, and start implementing the protocol on the 1426.

[JeffL]

Hi Sandeep,

As I said before, I believe you need to set the trigger type to External in LabVIEW. Your VI does not show this, at least by default.

As for not getting the results you expect, are you able to see the length of the high on the output? Or is it too short? It might be better to set up an image capture to ensure you're actually testing correctly.

The BNC should have ground on the outside, which you could set to digital ground on the Dsub.