Problems Scaling a Signal with a FPGA!!!

[flote]

Hi!!! I am working with this system:

1) NI 5761 The ADC Module:

Sample rate: 250 Ms/s

14 bits of resolution

4 channels simultaneously sampled

2) NI PXI-795xR:

FPGA Xilinx Virtex-5 SXT

Recomended for high-speed digital signal processing

Continuous filtering is a typical application

3) NI PXIe-1073

Chassis with 5 slots for the NI Cards.

MXI-Express controller integrated to link with the host computer at least at 208 MB/s

And I am trying to sacale a signal but I get something extrange. Anyone know what is happening?

[flote]

no body know this problem???

[Jennifer O]

It is hard to tell from the picture you have shown.  It appears like you are trying to scale by half, but that perhaps every other sample being returned is zero.  Without knowing more about how you are trying to scale the data it is hard to guess as to why you are seeing this behavior.

The NI 5761 adapter module has a few different CLIPs: Single Sample, Multi-Sample and Low Speed. Which one are you using?  Did you start with an example program such as "NI 5761 Getting Started"?

The Getting Started example uses the Multi-Sample CLIP, and packs two samples per cycle into a FIFO to pass back to the host.

 

The raw binary data is unpacked and scaled to volts in the host VI.  Are you attempting additional scaling inside of the FPGA code or at the host?  Are you working on two samples in parallel to scale both samples from the Multi-Sample CLIP? Check for the data types within your scaling algorithm (U16, U32, I16, I32 ?) to make sure you aren't inadvertently coercing the data to cause the problem.  If you are still having difficulty, perhaps you could post the VI or a picture showing what you are doing, and also provide details on how you need to scale the data ( simple multiply/divide by power of 2, linear etc).

[flote]

Hi Friend!!! Thanks for your reply Finally I solve the problem. My problem was in the Multiplier. I used a Saturation Multiplier to scale the Signal (http://zone.ni.com/devzone/cda/tut/p/id/3661) and this multiplier does not work properly. So you have to use a regular multiplier to do it!

Thanks