FPGA : Sample Rate Setting

[labview_jumper]

Hi,

I am new to Labview. I want to acquire data from Signal Generator (215kHz Signal) with max Sample Rate (max 750Ks/s).  I use a FPGA PXI-7853R , how can I do this ?

thanks.

[Alex.T]

Hi labview_jumper,

You can select the data rate within the FPGA for a supported module as follows:

1. Open up an Empty Project from the LabVIEW Getting Started screen.
2. Save and name your project.
3. Right click on the name of your project and select Targets and Devices and select your device under the existing targets.
4. Click OK.
5. When your device appears in your project, right click on it and select connect to establish a connection. See this article on how to configure the network settings for a PXI. Ensure that you allow FPGA Interface to be configured and not Scan Mode. Scan Mode used to just to route signal data through the FPGA module when you are using systems which rely on just the Real Time Operating System.
6. Right click on the FPGA Target and select New > VI.
7. In the Block Diagram, open the FPGA I/O Palette and drop an I/O Property Node.
8. Right click on the Property Node and select Select Item > FPGA Target then click on the particular module you want to interface with. It'll appear as the name of the Property Node. If you click on the Property, you can then configure the Data Rate from the module from there and can thus acquire signals from the module at the rate you specify.
9. Via use of a DMA FIFO, (Right click in the project under your RT target and Select New > FIFO) you can configure data transmission and receipt between your RT Target and FPGA. From the RT system you can process your data accordingly, and transmit to PC via a similar FIFO. Try reading up on this article to understand target and host communication.

Hopefully this should get you started!

Regards,

[AlexNCSU]

Hello,

Just to point out.  If you are trying to aquire a 215kHz sine wave, then the 750kS/s of the 7853R will not work so well.  Sampling at 750kHz, the 750/215 = ~3 data points per cycle of the sine wave and your signal will look mostly like random noise.  If the 215kHz is simply the output rate of e.g. a laser sensor, then you should be fine (since the actual signal you are trying to aquire is not going to be an e.g. 215kHz waveform).  What I am refering to is Aliasing and Nyquist Frequency, more info can be found here:  http://www.ni.com/white-paper/3000/en.  You must sample your data (rate at which you collect each data point, which for the 7853R is 750kS/sec or 750kHz sampling rate) significantly faster than the Frequency of the signal being measured.

Regards.