Troubles with HSDIO NI 6556: Can't generate at high frequencies because of a huge rise time

[AnalogKid2DigitalMan]

Jesse:

I see your point regarding the 50 ohm termination after further study of the device, 50 ohm is only recommended for the most demanding applications to maintain the transmission line.

Mar1:

Any chance all you probes need to be trimmed? I doubt it, but you may want to check. Most scopes have a square wave output you can connect the probe to to adjust the trim capacitor for the the sharpest rise/fall times with minimal over/under shoot.

-AK2DM

[Jesse_O]

If you look inside the PXIe-6556 specifications document on page 21 you will see a few eye diagrams of a 200Mbps signal.  Here you can see the eye diagram the rise and fall times are much smaller than what you are measuring. 

You mentinoned measuring several channels, which are moslty independent.  If you are able to generate a DC signal at the right voltages, and generate slow patterns with the expected outputes (i.e. generating 110100011 or any other data pattern) I would not expect a problem on channel 0 to cause problems on PFI 4 clock out (you mentioned testing these two channels). 

[johnsold]

The rise times shown in your images correspond to 200 nF driven through 50 ohms.  A capacitance that large is not likely in your cables or probes.

I did not see an answer to the question about grounding.  I wonder if the source and measurement devices are not properly grounded to each other? I have seen some strange "filtering" effects from improper grounding.

Lynn

[Mar1]

Hi all, I resolved this problem by making a self calibration! I think that some internal parameter went wrong.Now I am able to reach 100Mhz toggling signals with no problems :))))

However, "self calibration" VI stopped after 7min with the following error message:

"Calibration failure

Additional error info : 2

Source: 134219776

Status code : -219430"

And I noticed another wierd problem: Channel 11 is incontrolable. It has a 10V voltage (all the time) and there is no way to control it.

It can be set to "aquisition/generation" modes but the voltage is 10V all the time.

I tried to drive it low/high(using any voltage levels) at 200Mhz, and I observed that it is moving a little bit up un down (barely 200mV) but I's still close to 10V.

What's wrong?

Thanks to all of you for your help

[Kurt-P]

Hey Mar1,

Could you make a new thread for this new error? It helps people in the future who have the same issue because the new question will be the first post instead of somewhere in the middle of the thread. Plus that thread is more likely to get traffic than this one. 

Thanks,

-KP