How many analog inputs can I connect to a PCIe 7852R through SCB-68?

[Biochemist_MU]

How many analog inputs can I connect to a PCIe 7852R through SCB-68? I have about 21 analog inputs and three SCB-68 boards that I can use. Howeverm I was going over the manual and found that only one of the SCB-68 is connected ad RMIO and the other two as RDIO.

Did I get this right?

Thanks

[JoeySpinella]

Hi Biochemist,

According to the product page, the NI PCIe-7852R has 8 analog inputs, 8 analog outputs, and 96 DIO lines. As you can see on the pricing tab of the product page, it is recommended to have 1 RMIO cable and 2 RDIO cables. The RMIO cable will be for the pin-outs for the 16 AIO channels and the RDIO cables will be for the DIO channels.

You will not be able to read 21 analog inputs with just this FPGA board. If you are interested in more analog inputs for an FPGA, I would recommend considering the CompactRIO platform, which has the FPGA in the backplane and allows you to expand to include more analog inputs using Analog Input C Series modules such as the NI 9220.

Does this clear things up?

[BassemShebl]

Well, the thing is we already bought the FPGA card and we are looking into expanding the analog inputs to our card. However, we want simultaneous sampling along with the highest bit resolution possible and fastest possible sampling rate.
Any ideas or recommendations?

Thanks

[JoeySpinella]

Hi Bassem,

According the the product page for the 7852R, we can achieve 8 channels of simultaneous analog input at 16-bit resolution and 750 kS/s. This card cannot be expanded to have more analog inputs. If you are interested in more analog inputs, we will need a separate card to get that functionality. Which card I would recommend depends on your needs:

What platform do you need? PCIe? PXIe? cRIO? If PCIe, do you have an additional PCIe slot on your computer?

Do you need a customizable FPGA, or are you just looking for high speed analog input (and what sample rate)?

How many more channels do you need? Is this a system you would hope to expand to include even more channels in the future?

Is this for development/research, or a rugged system for field deployment?

As a note, if you are looking to process the analog input on the same FPGA of your existing 7852R, we will need FlexRIO cards with P2P streaming.

[Biochemist_MU]

Okay. Here are the details: We are building in our research lab an ultra-high resolution optical tweezers

We have to connect at least 16 AIs to the FPGA card - we want the system to be expandable so that later on we could connect more QPDs and other sensors or instruments to it.

We need at least for those 16 AIs to be measured simultaneously. We need the highest bit resolution possible (16 bit?) We want capacity for upgrading and adding more QPDs for example at the same standards.

Everything need to be connected to the same PC since we will have several cards that will provide feedback to and from the instruments connected to the FPGA.

The sampling rate would be at least 30-50 kHz.

We already have the PCIe 7852R FPGA card on that PC.

So here by I rest my case 🙂

What's your recommendations? Is there any way to upgrade our card by using an extension chassis? Do we need to replace our card with something else? Is there a technological limit on the number of AIs that can be used simultaneously and if yes what is it?

Thanks

[JoeySpinella]

Hi Biochemist (I am assuming you and Bassem are not working on the same project).

Our PCIe-FPGA cards all are limited to 8 AI and 8 AO, so unfortunately, you will not be able to use one FPGA PCI(e) card to do all of this data acquisition and feedback. There is not a way to upgrade a PCIe-FPGA card - it is fixed in its input and output capabilities.

What are your analog output needs for outputting the feedback? Are you doing the feedback calculations on the FPGA or bringing them back to the computer for calculations and analysis?

Here is what I would recommend:

Using a CompactRIO for your system.

cRIO is a platform that consists of a Real-Time controller, an FPGA back plane, I/O modules that can plug into the 4-8 slots on the back plane, and an interface to LabVIEW to program it from your computer.

This is a helpful tool for building a cRIO system and explaining how the parts fit together: CompactRIO Advisor

For your needs of using an FPGA to run quick feedback control and having expandable I/O, cRIO will be perfect. You could start with an NI 9205 module, which has 32 SE Analog inputs (16 differential). This would take only one slot of a 4-slot NI cRIO-9076, which has an Spartan-6 LX45 FPGA in it. You could then also get an Analog Output module to send feedback such as a 16 channel NI 9264. For a larger FPGA, you could also check out the cRIO 9081 and 9082, which are integrated cRIO's that can run Windows OS on them. With a cRIO, you could expand indefinitely, adding up to 8 I/O modules in a single cRIO, and also potentially adding an ethernet expansion chassis.

As a side note about Peer-to-Peer streaming and FlexRIO's as I mentioned in my last post, I wanted to clarify that P2P streaming can only be done between 2 FlexRIO cards in a PXI chassis. We are not able to do P2P streaming with PCI-FPGA cards such sa the 7852R. Here is a helpful article about Peer to Peer streaming if you are interested: An Introduction to Peer to Peer Streaming

[JoeySpinella]

As a further addition to my answer, I realized there was another potential solution I did not mention. This is in answer to your question:

"What's your recommendations? Is there any way to upgrade our card by using an extension chassis? Do we need to replace our card with something else? Is there a technological limit on the number of AIs that can be used simultaneously and if yes what is it?"

You may consider using the NI 9151, which will connect to your R Series card and allow you to use C Series modules to customize your I/O. This will take the place of existing I/O you have on the card (you will not still be able to use the 8 AI, AO and 96 DIO ports on the card). Instead, you can then fill the R Series Expansion Chassis for C Series I/O with C series modules like I discussed in my previous post.

With this expansion chassis, you would be able to achieve a maximum of 128 single ended 16-bit Analog Inputs with 4 NI 9205 Analog Input modules. However, keep in mind that if you also needed to perform analog output or DIO, you would need C series modules in the expansion chassis to perform those functions.