Get Better Measurements Faster Using Oscilloscopes With User-Programmable FPGAs

Instruments like oscilloscopes use multiple layers of software—some more visible to the user than others. Software on a PC controls overall test system execution, instrument drivers allow communication with the oscilloscope, and software embedded on the instrument itself controls how data is acquired and provided to the user. While traditional instruments provide fixed measurement capability through an instrument driver, modular instruments make use of open PC software and the processing power of modern CPUs to execute signal analysis on the PC instead of inside the instrument. This means you can  quickly customize the analysis performed on acquired data to meet your specific needs such as improved test times or higher resolution measurements.

Software-designed instruments take this concept one step further by giving you the ability to modify or even completely replace the embedded software running directly on the instrument’s FPGA. You can implement custom real-time analysis and complex triggers with no dead time (missed signals) because every acquired data point can be analyzed in real time on the instrument’s FPGA. In short, software-designed instruments give you the option to access all software layers—from the host PC down to the pins of an instrument’s data converter—to implement custom changes that meet the demands of your specific application.

NI offers a number of reconfigurable oscilloscopes that feature up to 400 MHz of analog bandwidth, eight input channels, 14 bits of measurement resolution, 1 GS/s sampling rate, and a user-programmable Xilinx Kintex-7 FPGA.

Whereas off-the-shelf instrumentation hardware traditionally has fixed capability, NI is leading the way in more open, flexible measurement devices based on FPGA technology. FPGAs are high-density digital chips that you can customize to directly incorporate custom signal processing and control algorithms into measurement hardware. The result is off-the-shelf hardware that has the best of both worlds—fixed, high-quality measurement technology; the latest digital bus integration; and user-customizable logic that is highly parallel, provides low latency, and is tied directly to I/O for inline processing and tight control loops.

FPGAs continue to gain design wins and market share from application-specific standard products (ASSPs) and application-specific integrated circuits (ASICs) because they keep up with Moore’s law better than other devices and dramatically lower development costs. This results in smaller test system size and lower power consumption. Very capable FPGAs are entering the market and defining the hardware capabilities of many devices, but the IP they contain is vendor defined and the FPGA’s power may be inaccessible to you. This is largely because the specialized hardware description language (HDL) knowledge needed to program these devices requires a steep learning curve and is generally restricted to digital design experts.

LabVIEW software makes the latest FPGA technology accessible. Using graphical programming, you can implement logic to define the behavior of an instrument in hardware and reprogram the instrument when requirements change. The graphical dataflow nature of LabVIEW is well suited for implementing and visualizing the type of parallel operations that can be implemented in digital hardware.

One instance of an instrument driver limiting your ability to use the full potential of an oscilloscope is invoking trigger modes. The oscilloscope IVI driver only allows for the use of a few trigger modes: edge, level, and window. An oscilloscope may have many more triggering modes, but the instrument driver can only configure the device to use those few. You may also want a very specific set of trigger logic that is not built into an oscilloscope that is available on the market. In this case, you could use the FPGA in the data path of the oscilloscope to program a logical trigger that will operate on the hardware of the instrument.

The LabVIEW FPGA Module extends LabVIEW system design software to FPGAs on NI reconfigurable I/O (RIO) hardware such as the PXIe-5171R and PXIe-5164 oscilloscopes, high-speed serial instruments, RF vector signal analyzers, and vector signal transceivers (VSTs), which introduced the concept of software-designed instruments in 2012.

Figure 3 shows the software architecture of a software-designed instrument (in this case, a reconfigurable oscilloscope). The architecture consists of routines implemented on the FPGA for the actual acquisition and real-time processing, as well as corresponding software modules on the host PC that interact with their FPGA counterparts to configure and control the measurements, handle the data transfer across the PXI Express bus, and present the data to the user.

Host PC components are very similar to instrument drivers; FPGA code is comparable to traditional oscilloscope firmware. In contrast to traditional oscilloscopes, you can use these components to build custom oscilloscope IP, and because they are open, you can modify and extend them to match specific needs.

NI offers several reconfigurable options for the PXI Oscilloscope. Oscilloscopes that have an FGPA include "Reconfigurable" in the model description on the oscilloscope category page.

Test Benefits of Oscilloscopes With User-Programmable FPGAs

One of the ultimate goals in test applications is to reduce total test cost. Time is often the main contributor to cost in high-volume manufacturing, while flexibility and reusability are important in high-mix or -maintenance test systems. Here are three examples that show how to save time and money by using oscilloscopes with user-programmable FPGAs.

Different industries, applications, and measurements require different oscilloscopes. To find out how reconfigurable oscilloscopes are reducing time to market and the cost of test, read more about each device family.

• See how engineers and scientists in semiconductor, aerospace defense, and research are using the PXIe-5170R and PXIe-5171R for smart, high performance systems
• See how test systems in automotive, semiconductor, and aerospace and defense are using the high voltage and high resolution of the PXIe-5164