PXI-6509 loopback

[mannyb]

I am trying to perfrom a simple loopback that requires for all lines (0-7) on port 0 to act as an output high (5V) and all lines(0-7) on port 1 as an input. All 18 lines are tied to each otner repectively (P0.0 to P1.0, P0.1 to P1.1...etc.). Using the test panel I enable P0 as an output and turn all lines high, then I configure port 1 as an input and watch the LED's light up. The way the LED's light up is erratic at best, this seems to point to a grounding problem but cant figure out how to resolve this issue. There is another post in the forum that deals with this same problem but the solution was never posted, and it was described as "user error".

[Jonathan_S1]

Could you describe what you mean by "erratic at best"?  Do the correct LED's light up in a non-timely manner, or do some light up and some not light up?  What kind of cable/ terminal block are you using? 

Thanks,

Jon S

[mannyb]

Erratic, some LED's light up, some do not, eventually after a while all LED's turn off. The terminal block I am using is the SCB-100, there are no active components in this unit or dip switches for special modes. I did try a pull down resistor for every loop of 1k to the card's ground, I will see if this works.

[Jonathan_S1]

How did the resistor work?  Usually LED's will burn up after a while if nothing is put in to limit the current that goes through it.

Thanks,

Jon

[Jonathan_S1]

Sorry Manny, I just realized you were talking about the LED's in your test panel.  Sorry about the confusion. 

Jon

[mannyb]

The 1k pulldown solution did not work, the LED's on the test panel are erroneously lighting up, need to try a new fix. I will say that someone from NI support suggested a 7.1k pulldown but unfortunately the card that was referenced was the PXI-6508 wich is a predecessor to the PXI-6509.

[TaylorG]

Hi mannyb,

In order to use the SCB-100 with a strictly DIO device, you must ensure that it is in DIO/Passthrough mode.  This can be done by setting the appropriate switches to the appropriate settings.  Verify that this has been done by consulting the section in the installation guide for the SCB-100 titled, "Using the SCB-100 with DIO/TIO Devices," which I have attached a link to.  Hope this helps!

SCB-100 Installation Guide

[mannyb]

The SCB-100 was installed as shown in the User's Manual. Thanks for the reply though.

[TaylorG]

Hi mannyb,

Has the issue been resolved?  Thanks!

[TaylorG]

Hi mannyb,

My apologies.  I was unsure after reading your last post if your loopback test was working!  Another thing you could check is your 100-pin connector from the SCB-100 to the PXI-6509 and make sure that there are no bent pins or anything that could be shorting, causing any unusual behavior on your test panel LEDs.  Thanks!