IRIG-B 6608

[nowellj]

I've read the NI documentation on how to hookup an IRIG-B signal to the PXI-6608 card, but I still cannot get the software to recognize the input signal.  If I've interpreted the document correctly, the IRIG signal get's attached to PFI7.  Am I missing any other connectiosn to the 6608?  I thought I just needed to connect this one line.  I know the IRIG signal is in the correct digital form the 6608 needs to do it's decoding.  Any ideas?

[nowellj]

As a followup, the NI example VI "Measure GPS Timestamp" is running correctly with the 6608 device.  However, the gpsTimestampCtr is essentially counting junk values.  I have a TB-2715 with wired as per the previous post, while the VI is running, if I remove the terminal block, the seconds count is unaffected.  Additionally, the timestamp display on the front panel is incorrect.

I have verified that I have an IRIG-B signal in the form the 6608 needs to decode it and I believe I have the appropriate connections made on the terminal block.  I've found a post on the NI forums with an identical problem to this one, but no solution, outside of verifying the input signal is correct, is listed.  Does anyone have any experience with this issue?

[S_Hong]

Hi nowellj,

If you have verified that the IRIG-B signal characteristics are indeed compatible to be used with the 6608 as described in this document, then I recommend trying a different GPS timestamp counter on the board since you have two on-board. If this doesn't work, can we also try changing the source of the GPS timestamp counter synch source to something other than PFI7?

Could you be more descriptive about what you mean when you say that the second count is unaffected when you remove the terminal block? Were the seconds on the front panel incrementing properly even though the time may be wrong?

Could you also link me to the forum post referring to a similar issue? 

Regards,

Message Edited by S_Hong on 03-26-2009 05:20 PM

[MattBradley]

I haven't used this particular card, but I have developed test systems for similar cards (IRIG, GPS, etc. signals).  One thing I would check on is make sure that the card is set to receive (rather than send) IRIG-B.  The cards I worked on could do both, but if you set it the wrong way it behaved just like you described.  Didn't have the same issue with the GPS signal because you could only receive it, not send it.

[Adam_U]

You might also consider the PXI-6682 if that's a better fit for this app...

[nowellj]

@S_Hong -  The forum thread is here http://forums.ni.com/ni/board/message?board.id=40&requireLogin=False&thread.id=2415  This is the same problem I'm having.  If the edge connector is on the card, it's not counting, in fact, the seconds count on the example VI are negative and are not incrementing, but appear to be bouncing around.  Removing the edge connector while the VI is running produces no change and does not cause the VI to error or or behave differently, leading me to conclude that the signal is not reaching the correct input line.

@MattBradley - That's something I hadn't considered.  I'd assumed that with this particular card, it was received/decode only.  I'll look through the options and see if it is infact trying to send IRIG information out.

@Adam U. - Funny story, we actually had the 6682 card in our possession as a chassis sync card; unfortunately, it isn't compatible with LabVIEW RT, which is why we're using the 6608.

Gentlemen, I appreciate the suggestions, I'll try them and see if I get any additional results.  I'll let you know of the results and the steps it took to fix it.

[Adam_U]

There's a beta out (of NI-Sync 3.1) which does support LVRT. If you're interested...

[nowellj]

I've implemented the suggestions S_Hong made and I've made some progress.  I switched to the gpsTimestampCtr1 as the primary decoder and moved the sync line from PFI7 to PFI8.  The card appears to be decoding the IRIG signal, but when I removed the edge connector from the card, it still counts up.  Additionally, if I change the decoder, I get different timestamps, and changing the PFI lines produce different timestamps as well. 

I'm really stumped.  On the one hand, the counter card is behaving more correct then it has in the past.  On the other hand, it's still incorrect.  I'll keep working on it and see if I can find another something else.

[MattBradley]

This is with a different card (again), but this has also been my experience.  If you remove the signal, the card keeps counting.  It uses the external signal to sync its internal clock.  By default, if the signal is gone, you lose the lock but it won't stop (unless you set it up that way).

[nowellj]

MattBradley,

    Thanks.  That makes sense now.  I had assumed that by connecting the IRIG signal to the input, that t he card would perform decoding on the signal, not just merely sync up it's internal counter.  In this case, the card may be reading the IRIG signal, somewhat correctly, but I just need to add in an offset.  Thanks again.