CompactRIO: A new class of embedded

Embedded systems have a substantial list of design constraints. The combination of cost pressure, real-time requirements, reliability/durability requests, and performance needs make it extremely difficult to successfully build a competitive embedded solution. National Instruments' CompactRIO represents a major change in embedded system design and introduces a new class of embedded solutions. CompactRIO is a low-cost, rugged, ultra high-performance embedded system that utilizes the processing power and flexibility of the Field Programmable Gate Array (FPGA) and the reliability of a real-time processor. This new embedded platform is built around the newly invented Reconfigurable I/O (RIO) technology, which allows FPGA chips to be programmed with high-level LabVIEW graphical development tools. Up until now, programming an FPGA chip required users to learn a complicated software environment such as VHDL, which has an extremely steep learning curve.

Figure 1: CompactRIO System
(Click graphic to zoom by 1.9x)

The CompactRIO low-cost embedded architecture provides open access to low-level hardware resources for rapid development of custom standalone or distributed control and acquisition embedded systems. Figure 1 shows the CompactRIO system. The entire CompactRIO system is programmed with LabVIEW graphical development tools, from the real-time embedded controller to the embedded FPGA. The result is an embedded system that lowers system costs while providing an increase in system performance and flexibility.

New class of embedded system design
CompactRIO reduces embedded design costs because there is no need to spend the time and money developing a custom mechanical enclosure. CompactRIO’s robust design is rated for a -40°C to 70°C (-40°F to 158°F) temperature range, 50 g shock, and hazardous locations or potentially explosive environments (Class I, Div 2). Most I/O modules feature up to 2,300 Vrms isolation (withstand), and 250 Vrms isolation (continuous). Each component comes with a variety of international safety, electromagnetic compatibility (EMC), and environmental certifications and ratings.

Additionally, CompactRIO is designed for extreme applications in harsh environments and small places. Size, weight, I/O channel density, and power consumption are critical design requirements in many such embedded applications. By taking advantage of the performance and small size of FPGA devices, CompactRIO delivers unprecedented control and acquisition capabilities in a compact, rugged package. A 4-slot reconfigurable embedded system measures 179.6 by 88.1 by 88.1 mm (7.07 by 3.47 by 3.47 in.) and weighs just 1.58 kg (3.47 lb). An 8-slot system filled with 32-channel I/O modules delivers a mass channel density of 9.7 g/ch (0.34 oz/ch), and a volumetric channel density of 8.2 cm3/ch (0.50 in3/ch). The typical power consumption of the entire CompactRIO embedded system is on the order of 7-10 W.

Figure 2 depicts the CompactRIO architecture. The architecture is composed of three main parts:

  1. The embedded real-time controller
  2. The reconfigurable embedded chassis containing the FPGA
  3. Hot-swappable I/O modules

The seamless integration between the embedded controller, the chassis containing the FPGA, and the plug-in I/O modules allows for superior embedded system performance. The direct connection between the I/O modules and the FPGA enables the developer to tightly integrate timing and triggering between I/O modules through the FPGA.

Figure 2: CompactRIO Architecture

The CompactRIO real-time embedded controller features an industrial 200 MHz Pentium class processor that reliably and deterministically executes LabVIEW Real-Time applications. Engineers can choose from thousands of built-in functions to build a multithreaded embedded system for real-time control, analysis, data logging, and communication. The NI LabVIEW Real-Time Module extends the development environment to deliver deterministic, real-time performance. Engineeers develop the real-time application code on a host computer using graphical programming and then download the application to run on the CompactRIO real-time controller that contains an off-the-shelf real-time operating system. The CompactRIO real-time controller also features a 10/100 Mbps Ethernet port for programmatic communication over the network (including e-mail), built in web (HTTP) and file (FTP) servers, and dual 11 to 30 VDC supply inputs.

The reconfigurable chassis is the heart of NI CompactRIO embedded systems, containing the RIO FPGA core. The RIO FPGA chip is connected to the I/O modules in a star topology for direct access to each module for precise control and unlimited flexibility in timing, triggering, and synchronization. A local PCI bus connection provides a high-performance interface between the RIO FPGA and the real-time processor. The reconfigurable chassis features the same rugged metal construction that characterizes the entire CompactRIO platform.

Each CompactRIO I/O module contains built-in signal conditioning and screw terminal, BNC, or D-Sub connectors. By integrating the connector junction box into the modules, the CompactRIO system significantly reduces the space requirements and the field wiring cost. A variety of I/O types are available including:

  • ±80 mV thermocouple inputs
  • ±10 V simultaneous sampling analog inputs/outputs
  • 24 V industrial digital I/O with up to 1 A current drive
  • Differential/TTL digital inputs with 5 V regulated supply output for encoders
  • 250 Vrms universal digital inputs

Open platform
CompactRIO is an open platform and allows embedded engineers to develop custom I/O modules to meet unique needs of their particular products and applications. National Instruments offers a module development kit to qualified engineers that includes all the tools needed for building:

  • Custom CompactRIO modules
  • Custom CompactRIO module development software
  • Complete technical documentation
  • The license right to develop and manufacture custom CompactRIO modules

The NI CompactRIO Module Development Kit also includes a set of CompactRIO module housings that provide a variety of connector options to best meet the requirements of the application. With the ability to design custom I/O modules and the custom hardware performance of FPGA-based RIO technology, CompactRIO gives embedded engineers complete control over the design of their embedded systems.

Performance and flexiblity
Using the power of the FPGA core in CompactRIO, engineers are designing 1 MHz digital control loops with no performance reductions with an increased number of logic computations and running 100 kHz analog PID control loops using 32-bit, integer-based calculations in the FPGA. Machine builders are using the speed and customization of CompactRIO to integrate ultra high speed motion control for multi-axis servo and stepper motors. With CompactRIO and NI Softmotion, engineers are implementing custom motion control algorithms in the FPGA of CompactRIO, and obtaining control loop rates as low as 5 µsec. NI SoftMotion Development Module for LabVIEW is for machine builders and OEMs creating custom motion controllers for better machine performance and for researchers implementing advanced control design algorithms for motion control. The module includes functions for trajectory generation, spline interpolation, position and velocity PID control, and encoder implementation on LabVIEW Real-Time and/or LabVIEW FPGA.

CompactRIO also allows engineers to easily and quickly redesign and upgrade their embedded systems when application needs change. The embedded FPGA in CompactRIO is programmed with LabVIEW, allowing engineers to customize and redesign their embedded systems in a short amount of time. When the system functionality needs to change, developers simply need to change their LabVIEW code and download a new silicon bit stream configuration to the FPGA hardware.

Application areas
Because of its low cost, reliability, and suitability for high-volume embedded measurement and control applications, CompactRIO can be adapted to solve the needs of a wide variety of industries and applications. Industry examples include:

  • Batch and discrete control
  • Custom motion control
  • Intelligent in-vehicle data acquisition
  • Distributed data acquisition and control
  • Mobile/portable Noise, Vibration, and Harshness (NVH) analysis

CompactRIO is already being used to replace the Engine Control Unit (ECU) on high performance motorcycles, to monitor wind turbines and power generators, and to perform flight data recording for the development of high altitude skydiving equipment. Application areas for CompactRIO continue to evolve as applications are completed in areas such as:

  • Heavy machinery control
  • Semiconductor control
  • Rapid Control Prototyping (RCP)
  • Industrial machine condition monitoring
  • Mobile/portable dynamic signal analysis

The CompactRIO architecture provides the ability to quickly design a customized, embedded solution using the processing power of an FPGA and the reliability of a real-time processor in a low cost, rugged form factor. CompactRIO provides embedded system engineers a definite answer to the long list of design constraints enabling them to lower embedded system costs and increase embedded system performance and flexibility.

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Todd Dobberstein
is an industrial data acquisition and control product engineer for National Instruments, focusing on Reconfigurable I/O (RIO) hardware such as CompactRIO and plug-in R Series devices. He joined NI in March 2002 as an application engineer and moved to the product engineering team in May of 2004. Todd holds a B.S. in electrical engineering from Kansas State University.

For more information, contact Todd at:

National Instruments
11500 N Mopac Expwy
Austin, TX 78759-3504
Tel: 512-683-5836