export sync in PXI-5421

[labmaster]

In PXI-5421, there is no Sync out port.

But, this can be controlled in LV by using Fgen Export Signal.vi.

I tried to export sample clock successfully.

But why I can't export Sync signal to PFI0 (or any ports)?

I used the same name of port with exporting sample clock.

(The "enum" type of port name cannot be changed.)

What do I export my current TTL of sine signal? 

Does anyone who have an example of exporting Sync?

labmaster

Message Edited by labmaster on 05-13-2009 12:06 PM

[kirsch]

The Sync signal is generated internally in NI function generators by passing the analog signal (the DAC's output) through a hardware comparator. This is true for the NI-5402 and NI-5406 function generators. The NI-5421 Arb does not have this hardware internally and thus, no Sync signal.

You can get a poor man's Sync signal out of the PXI-5421 by routing the most significant bit of your data. Use the Data Bit properties to do this. Depending on how many samples are used internally to create your sine wave, you may see a little bit of jitter. Hopefully this works for your application. 

Good luck

Marcos 

[labmaster]

Thank you, Kirsch.

Do you really mean I can't use "Sync signal" of current sine wave by routing to PFI0?

In realtime, I need TTL(Sync) signal for other instrument (like Lockin reference) of current waveform.

Can you explain me in detail about a way of using data bit properties or any other methods to export to PFI0?

(I am a beginner with PXI-5421).

labmaster.

Message Edited by labmaster on 05-13-2009 04:53 PM

[labmaster]

I got to know the concept of how-to-do.

Does you mean marker properties of generated wave?

This content was shown in tutorial document of FGEN.

(http://zone.ni.com/devzone/cda/tut/p/id/5534)

I will try it tomorrow and post it again.

labmaster.

Message Edited by labmaster on 05-13-2009 10:01 PM

[kirsch]

To avoid confusion: There are Markers and Data Bit Markers in NI-FGEN.

Marker Events are used in Arbitrary Waveform mode (you download your waveform data to the instrument), not in Standard Function Mode (you tell the instrument which function to generate: sine, square, triangle...). You place them at some specific sample and they are generated when the arb is generating that sample.

Data Bit Marker Events are simply a specific bit of the data going to the DAC that you can route out.

Since you are generating a sine wave, I assume that you are using Standard Function Mode. So you can't use Markers. I was proposing you use Data Bit Markers. The most significant bit of the digital data of a sine wave is the sign. This is basically the same thing as a Sync signal. So what I'm proposing is that you configure the DataMarker0Event to come out a PFI connector and set the DataMarker0BitNumber property to 15 (the most significant bit). We ship a LabVIEW example with NI-FGEN that shows how to use Data Marker Events.

Hope this clarifies things.

Marcos 

[labmaster]

Kirsch, thanks so much for the caring me.

Fortunately, I used script mode to control the waves.

Anyway, I found a NI example (Fgen Arb Waveform Marker.vi) for this and appled to my code. It looks no problem.

I am not specialist for signal generation and processing.

1. Would you please explain me why I need to do step #6 in the example? 

"6 - Configure the analog data mask and static value so the data
     markers are not generated on the analog output."

Do I have to do it for reliable frequency of waveform signal or TTL?

I want to use TTL signal to Lockin input. 

2. My generated waveform is "waveform" type.

But most NI FGEN examples use "integer I16" including example above.

I would like to know if there is a spcial reason (something like more precision or fast) to do this?

Thank you again.

labmaster

[kirsch]

6 - Configure the analog data mask and static value so the data markers are not generated on the analog output.

Data markers are basically bits of your digital data being routed out to a PXI_Trig or PFI line. Analog data mask lets you mask out some of the bits in your digital waveform data so that they never make it to the DAC. The 5421 is a 16-bit arb. The idea here is that you trade off waveform resolution by sacrificing the lowest bit(s) of your digital waveform (you mask them out from going into the DAC) in order to use them as data markers.

You can write waveforms to the Arb as F32 from -1 to 1 or I16 data. If you use F32, the driver scales the data to I16 anyway because that's what the DAC in hardware uses. So if you write I16 data, you bypass the scaling - it's a little bit faster and of course I16 uses half the memory on the computer (not on the Arb, on the Arb the data is always already scaled to I16). So you can use either one, whatever is easier for you. However, in the specific case of data markers, you want to use I16 data so that you can replace some of the bits with the data marker information... you wouldn't be able to do this on F32.

Hope this clarifies it.

Marcos 

[labmaster]

kirsch,

I visit again your posting to solve my problem.

Can you give me an idea for sync signal when I have to use a waveform with a great negative offset?

I found the sign bit is not changed in negative offset sine wave.

Labmaster.

[labmaster]

Kirsch,

Currently, I use script mode and waveforms (means internally DBL) as a input data instead of I16.

Do I have to transform the wavform data type to I16?

labmaster