How many FPGA gates should I choose for a Ni 7831R?

[Jingyan]

I notice there are two options about FPGA gates for Ni 7831R : 1M or 3M. But I am really not sure about what is the corresponding memory for these options and how large VIs or algorithms I can download to these FPGA gates.

Basically I want to use Ni 7831R to control a MIMO nano-positioning stage with servo rate above 50kHz. The controller could be pretty complex. The order of controller would be more than 20. We use three AI channels to get feedback signal and three AO channel to send out control commands. I am wondering if !M gates enough for these purpose?

Another question is about software. Do I have to use softMotion Module to develop a controller? Actually at current stage, we don't care too much about trajectory generation. Could We only use FPGA module to develop the controller and generate some simple trajectories (such as circle) offline and send these target position to the FPGA board through FPGA module? Actually I am going to order a Ni 7831R very soon. I need to know if I really need to buy the  softMotion Module or not.

The last thing I am quite interested in is the quality of the AI and AO channels of the Ni 7831R. What is the noise level from the AI and AO channels? I know it has 16-bit resolution. But some I/O channels I used before could give more than 10mv noise, which is much higher than announced resolution.

Thanks

Jingyan Dong

[Thaison_V]

Jingyan,

I hope you're doing well.  It looks like you're looking at using one of the R Series boards for your application.  Regarding the number of gates, it is very difficult to determine ahead of time what applications will fit on a 1M or 3M gate.  The general rule is that if you are just doing data acquisition (including timing, triggering and synchronization), 1M usually will work.  If you are adding a control algorithm or other signal processing, you will likely need 3M gates.  This is from the following FAQ on R Series boards on the DeveloperZone.

For your SoftMotion question, I would pose the question on the Motion Control and Motor Drives board.  Our Motion engineers will be the best people to answer questions regarding this.

Lastly, the analog input and output of the 7831R should meet the Accuracy Specifications found in the 783XR User Manual on page A-2.  This does not include noise from your sensor or external connections.  If your board that you were using previously is seeing 10 mV noise and you've determined that this does not meet the specifications, let us know and we can help you troubleshoot the board.  Have a great day!

Thaison V
Applications Engineer
National Instruments

[Jingyan]

Thaison ,

Thank you for your reply. Actually I intended to post the question in Motion control and motion driver board, but I don't why it come here. I will repost my questions in that board.

Jingyan