DAC output without using DAC configure mode

[LuPmA]

Hi,

I am using NI-5640R and labview 8.2.

Is it possible to send out anything without using DAC configure (single or quadrature) mode?

Actually, what I am trying to do is to send out to DAC whatever comes in, like attachment

Ahmet

[Mauricio Capistran-Garza]

Hello Ahmet,

You can look at the example called ni5640R Frequency Translation. I think it does exactly what you are trying to do.

- Mauricio

[LuPmA]

Hi Mauricio,

I think I could not clearly tell my problem.

1)Let say I have digital data which I want to transmit, If I use DAC configure (single or quadrature) mode block, I just see a sinus that I can only change frequency. So I can not transmit my data, right??

2)For Frequency Translation example, it is not what I want, because I want to transmit whatever I get on ADC without sending to host computer.

And, also I have looked all examples, but none of them does what I am looking for.
 

I am looking for your response.

Best Regards

Ahmet

[Mauricio Capistran-Garza]

Hi Ahmet,

The Frequency Translation Example acquires data on ADC 0 inside a Single Cycle Timed Loop (SCTL) that runs on the ADC Clk and then uses a FIFO (named "Local") to send the data to another SCTL that runs on the DAC Clk. On the second loop it reads the data from the FIFO and generates it. Additionally, it also sends the acquired data to the host via a DMA FIFO (named "DMA").

You will not be able to put the ADC and DAC I/O Nodes inside the same SCTL because each is running of a different clock.

- Mauricio

[LuPmA]

Hi Mauricio,

Then the attachment should work properly, right??But it is not working, I mean I can see signal on the host computer but I can not transmit to DAC in order to see it on the osciloscope screen.

1)Can you please tell me my mistake??

2)Even for IQ Output example, If I take "DAC Configure for Single-Tone" vi out, then it is not working. I still could not understand how I can transmit my data without using that vi??

Thanks,

Best Regards

Ahmet 

[Mauricio Capistran-Garza]

Hi Ahmet,

You are right, I over simplified the answer. I'll try to take it from the top. The ADCs and DACs on the board have integrated Digital Downconverters (DDCs) and Digital Upconverters (DUCs) respectively. You can find in the documentation a description of how this work, but the basic idea is that the DDCs do two things: 1) Mix the input signal with a specific carrier frequency, taking the signal to 0 Hz, 2) Filter the signal with a specified bandwidth. The DUCs (inside the DACs) do the inverse: they take a signal that is in baseband and generate it at a specified center frequency. So, in order to use them you MUST configure the DDCs and DUCs insde them, and that is what the "DAC Configure for Quadrature Mode", and "ADC Configure NCO" and "ADC Configure DDC" do. So yes, you must have a host VI that configures the device before you can get it to work.

By the way, there is another problem with the screenshot that you sent. The IO Node named "DAC_0_Data" expects I and Q values interleaved in time. What that menas is that in one clock cycle you must write the I and in the other the Q. You can see the examples to see how that is done.

- Mauricio

[LuPmA]

Hi Mauricio,

I saw your video for NI-Week, you were transmiting a song to different  freq.,  is that right?Ok, What I don`t understand is whenever I use "DAC Configure for Single Tone Mode", I get just a sinus on the oscilloscope screen, it is not my data , I want to transmit whatever I get on ADC, or my own data, not a sinus.

How did you guys transmit that song, If "DAC Configure for Single Tone Mode" transmit only a sinus??

Is this too ridiculous question?? I mean I think I can not do most basic thing.

Thanks

Ahmet

[Mauricio Capistran-Garza]

Hi Ahmet,

So, the DAC has two modes in which it can work. The first is the Single Tone Mode, in which case you don't have to provide any data, it automatically generates a tone at the specified frequency. The second mode is called Quadrature Mode. In this case the DAC does expect you to provide the data. It's called Quadrature Mode because it expects IQ data (quadrature encoded data). So you have to use the DAC Configure for Quadrature Mode VI for what you are doing. Also, make sure you are acquiring at the same rate as you are generating, otherwhise you will overflow or underflow the generation.

-Mauricio

[antonio.matar]

Hi there:
I am also using the the NI PCI-5640R and I've been "studying" the program: "Frequency Translation", my intention is to modify it and produce a  closed-loop between I and O. 
I am also interested in transferring what i am reading through the input port, directly to the output port but filtered and with a phase-shift (final Objective: Q-Control). 
I need to visualize the signal in the HOST, so I need both FIFOS (DMA FIFO and  Local FIFO), and the "Quadrature Mode DAC Configure"

I would like to know:
1. How can I directly transfer the data acquired through the ADC port into the DAC?  (it is unclear due to the Event structure in the "Frequency Translation" example)
2. How can I configure the "Quadrature Mode DAC Configure.vi" for it to bandpass-filter the signal comming from the ADC at a given frequency and BW, specified by the user in the HOST?
3. Is it possible to configure the "Quadrature Mode DAC Configure.vi" to produce a phase-shifted signal (phase shift also specified by user in the host)

I've been working for almost 2 months trying to program the 5640R, doing examples, and modifying them.  After playing with different examples I've come up to the conclusion that the "Frequency Translation" example is the one that best-suites my application.  My problem now is that I AM LOST because i need more information regarding the configuration parameters of ALL the different VI's inside the NI-5640R VI Tree  to exploit them correctly, specially the "Quadrature Mode DAC Configure.vi".

Can anyone please help me?
Cheers, Antonio