R Series Intelligent DAQ Frequently Asked Questions (FAQ)

What are the new R Series devices?

Figure 1.  New R Series Intelligent DAQ modules with faster I/O and Virtex-5 FPGAs

The new R Series Intelligent DAQ modules (shown in figure 1) are the PXI-7841R, PXI-7842R, PXI-7851R and PXI-7852R. Table 1 shows the new R Series modules and their features such as 750 kS/s simultaneous analog input rates, 1 MS/s simultaneous analog output rates, and new high-performance Virtex-5 field-programmable gate array (FPGA) chips. Each of the four new NI R Series intelligent data acquisition (DAQ) and control modules is configurable with the NI LabVIEW FPGA Module.

Table 1. R Series Intelligent Data Acquisition and Control Devices

These intelligent DAQ devices feature user-defined onboard processing as well as complete I/O timing and triggering flexibility. You can configure all device functionality by creating LabVIEW block diagrams with the LabVIEW FPGA Module. Your block diagram executes in hardware, giving you direct, immediate control of all I/O signals on the PXI or PCI device. With R Series and LabVIEW FPGA, you can configure user-defined hardware for a wide variety of applications requiring precise timing and control such as:

• Data acquisition with onboard processing
• High-speed analog and discrete control loops
• Pulse-width modulation (PWM) and encoder interfacing
• User-defined digital communication protocols
• Custom counters with up to 64-bit resolution
• Hardware-timed decision making at 40 MHz

Learn More about R Series Devices

 

 How do the new R Series modules compare to previous-generation R Series devices?

The new R Series modules are equipped with high-performance Virtex-5 FPGAs, which deliver improved optimization capabilities that provide faster code execution and more LabVIEW code capacity than previous-generation R Series devices. Virtex-5 FPGAs feature a new 6-input look-up table (LUT) architecture for substantially improved resource utilization as well as DSP slices that make it possible for you to implement more complex digital signal processing at faster rates. The new Virtex-5 LX30 FPGA is approximately twice the size of a Virtex-II 1M gate FPGA, and the new Virtex-5 LX50 FPGA is slightly larger than a Virtex-II 3M gate FPGA.

In addition, the new NI PXI-7851R and PXI-7852R modules can sample up to 750 kS/s on all eight analog input channels with 16-bit resolution. PID control loops can run more than 3.5 times faster than previous-generation R Series hardware, and, with FPGA-based parallel execution, multiple control loops do not have to compete for processor bandwidth. Faster analog input rates also improve analog triggering precision and frequency measurement capabilities.

The new R Series modules also require a new version of the NI-RIO driver (Version 2.4 or later). If you have an earlier version of the NI-RIO driver for R Series devices, upgrade to the latest version for free.

 

How many gates are there in the new Virtex-5 FPGAs?

The number of gates has traditionally been a way to compare FPGA chips to ASIC technology, but it does not truly describe the number of individual components inside an FPGA. This is one of the reasons why Xilinx did not specify the number of gates for the new Virtex-5 family. LabVIEW FPGA benchmarks have shown that the new Virtex-5 LX30 FPGA is approximately twice the size of a Virtex-II 1M gate FPGA, and the new Virtex-5 LX50 FPGA is slightly larger than a Virtex-II 3M gate FPGA.

 

How do I decide which FPGA is right for my application?

Unfortunately, it is difficult to determine whether an application or program will require a larger or smaller FPGA. The LabVIEW FPGA Module and NI-RIO driver give you the ability to compile block diagrams without having any hardware at all, so the best way to see how many resources you need is to try it out.

You can use the following as a general guideline when deciding which FPGA works for your application.

For an application that performs basic timing, triggering, and synchronization on the FPGA, you can use a smaller FPGA. If the application includes timing, triggering, and synchronization along with additional signal processing on the FPGA (control, digital filtering, complex analog triggering), you need a larger FPGA that has more resources to implement those operations.

For more information on how FPGAs work at a lower level, read the FPGAs - Under the Hood white paper.

 

 Will my Virtex-II program work on a Virtex-5?

In general, a program compiled for a Virtex-II 1M gate FPGA should also compile for a Virtex-5 LX30, and a program compiled for a Virtex-II 3M gate FPGA should also compile for a Virtex-5 LX50. Due to architectural differences between the two FPGA families, there are no guarantees, and the only way to see if a program will migrate between families is to try it out.

With the LabVIEW FPGA Module and NI-RIO driver, you can compile block diagrams without having any hardware at all. To add support for the new Virtex-5 R Series targets, simply upgrade to the latest version of NI-RIO for free.

 

 What are the benefits of Virtex-5 FPGAs?

Figure 2. NI PXI-7852R with Virtex-5 FPGA chip circled in red

The Virtex-5 FPGA architecture is optimized to execute faster and more efficiently using single-cycle timed loops in the LabVIEW FPGA Module. The fundamental building blocks for implementing digital logic inside FPGA chips are called slices, and each slice is composed of flip-flops and look-up tables (LUTs). Previous-generation Virtex-II FPGAs use 4-input LUTs for up to 16 combinations of digital logic values. The new Virtex-5 FPGAs use 6-input LUTs for up to 64 combinations, increasing the amount of logic that you can implement per slice. In addition, the slices themselves are placed in closer proximity to each other to reduce the propagation delay of electrons and increase overall execution rates. What does this mean for LabVIEW FPGA applications? The single-cycle timed loop structure takes advantage of six-input LUTs for substantially improved resource utilization. This means you can optimize more LabVIEW FPGA code to fit within Virtex-5 FPGAs and perform more operations per clock cycle.

For example benchmarks that compare the size and speed of new Virtex-5 LabVIEW FPGA targets, see LabVIEW FPGA Benchmarks for Virtex-5 R Series targets.

 

Do I need to know VHDL to use LabVIEW FPGA?

No. Using the LabVIEW FPGA Module, you can synthesize graphical code directly from LabVIEW to the FPGA on R Series devices. While understanding how LabVIEW compiles the graphical block diagram to VHDL can help you understand optimization trade-offs, you do not need to understand FPGAs or VHDL to use LabVIEW. LabVIEW is ideal for engineers who need the hardware customization that FPGA technology offers but do not know or understand low-level hardware description languages such as VHDL or Verilog.

Learn More about the NI LabVIEW FPGA Module

 

Do I need the LabVIEW FPGA Module to program R Series devices?

Yes, you must use the LabVIEW FPGA Module to program R Series devices. However, if you have existing VHDL IP cores or other VHDL code you wish to use, you can integrate VHDL into a LabVIEW block diagram using the HDL Interface Node.

Read this application note to learn how to integrate VHDL into a LabVIEW block diagram.

 

How is R Series different from other data acquisition families?

Instead of a fixed ASIC for controlling device functionality, R Series offers a user-programmable FPGA chip for onboard processing and flexible I/O operation. Multifunction R Series intelligent DAQ devices feature a dedicated analog-to-digital converter per channel for independent timing and triggering. This offers specialized functionality such as multirate sampling and individual channel triggering, which are beyond the capabilities of typical data acquisition hardware. You can define the hardware-timed digital I/O on R Series devices as counters, PWM channels, flexible encoders, or lines for digital communication protocols.

 

Can I program R Series devices with NI-DAQmx, NI-DAQmx Base, or the NI Measurement Hardware DDK?

All R Series intelligent DAQ devices use NI-RIO driver software – they are not compatible with NI-DAQmx or NI-DAQmx Base. There is support, however, within the NI Measurement Hardware DDK for custom driver development through register-level programming. Once you have compiled and downloaded a LabVIEW FPGA application to an R Series target, the NI MHDDK provides documentation for the host application to interface with registers on the FPGA across the PCI or PXI bus. 

 

What are the R Series onboard processing capabilities?

The LabVIEW FPGA Module includes a signal processing palette with numerous functions such as:

•        PID control

•        Butterworth filters (highpass and lowpass)

•        Notch filters

•        Analog period measurement

•        DC and RMS measurement

You can easily implement functionality such as digital debounce filters and watchdog timers in LabVIEW, and you can find many more functions and examples on the LabVIEW FPGA IPNet.

 

 Can I achieve simultaneous analog input/output with an R Series device?

Yes. All multifunction R Series devices have dedicated analog-to-digital converters and digital-to-analog converters on every analog input/output channel, making it possible to sample/update all channels simultaneously or at different rates. With independent analog-to-digital converters, you can sample every channel on the device at the maximum rate (up to 750 kS/s). You can program the independent digital-to-analog converters to update analog output channels at rates up to 1 MS/s.

The LabVIEW FPGA block diagram in Figure 1 shows how easy it is to implement simultaneous analog input/output on R Series FPGAs. By using a LabVIEW FPGA Analog Input I/O Node that is reading from all eight channels of the NI PCI-7833R board in the same while loop, the program samples from all eight channels at 200 kS/s simultaneously. The lower loop running in parallel uses the LabVIEW FPGA Analog Output I/O Node and updates all eight analog output channels at 1 MS/s.

Figure 2. Simultaneous Analog Input/Output with R Series and LabVIEW FPGA

   

 What are some other LabVIEW FPGA capabilities?

LabVIEW FPGA can meet a myriad of unique application challenges that often require custom hardware. Below is a short list of the tasks you can implement using LabVIEW FPGA and R Series:

• Signal processing functions such as filters and fast Fourier transforms (FFTs)
• Digital communication protocols
• High-speed analog and discrete control loops
• Custom motion control
• Analog and digital signal generation

For an extensive list of LabVIEW FPGA functions and examples, visit the LabVIEW FPGA IPNet.

Reader Comments | Submit a comment »

RE: NI Measurement Hardware DDK
Good question. A section was added that discusses software support for R Series devices labeled "Can I program R Series devices with NI-DAQmx, NI-DAQmx Base or the NI Measurement Hardware DDK?"
- Mike L, National Instruments. - Feb 28, 2008

NI Measurement Hardware DDK
This page doesn't say what software works with the R-series devices. Does NI-DAQmx 8.3 work? How about base DAQmx? How about the NI Measurement Hardware DDK?
- Feb 5, 2007

Out of date
- Mar 20, 2006