Designing OpenVPX:

High-Performance Architectures for Future-Proof Defence Applications

OpenVPX is an open embedded computing standard, which is mainly used for military and defence applications. It offers robust and interchangeable modules, giving developers a high degree of flexibility when designing with OpenVPX. For example, developers can select different slot and backplane profiles, decide which data buses and interfaces they want to use and which cooling concept they want to rely on. 

Therefore, it is important to decide as early as possible in the project which components are best suited to avoid costly changes later in the project. This is the only way to ensure that developers can provide customers with a scalable, efficient, powerful and robust design. 

Another important aspect of the embedded design is the future viability of the application. VITA, which introduced the OpenVPX standard, provides this via so-called VITA extensions. These are adapted by manufacturers such as Sundance or Etion Create to deliver modular and innovative OpenVPX products. 

Which Component for Which Application?

When designing OpenVPX applications, developers can choose from a variety of system components, which are generally divided into modules, backplanes, and enclosures. This opens a wide range of possibilities but presents developers with a difficult decision as to which components are best suited to their application. For this reason, an overview of the main individual components is provided.

Modules: An OpenVPX Module Profile defines the communication protocols on each of the Pipes defined in the Slot Profile. The Module Profile specifies a specific Slot Profile and module height (3U or 6U). This definition provides a first-order check of operating compatibility between the different Modules and the Backplane intended to be used in a Chassis. Module and Backplane Profiles guide system integrators in their selection of compatible plug-in Modules and Backplanes. OpenVPX defines the following Module Types, with examples given below:

  • Payload card, e.g. Processor modules for CPU-, GPU- or FPGA-based architectures
  • Storage card, e.g. SATA and PCIe
  • Peripheral card, e.g. I/O modules or modules for AI acceleration, software-defined radio
  • Switch card, e.g. PCIe and/or Ethernet switch
  • Bridge card, e.g. for the VME bus
  • Others, such as Timing cards

Slot Profiles: An OpenVPX Slot Profile is a physical mapping of Ports onto a given slot’s Backplane Connectors. These definitions are often made in terms of Pipes. Unlike Module Profiles, a Slot Profile never specifies protocols for any of the defined Ports. Profile Parameters are used to further describe properties of a Slot Profile. All modules are standardised in two different slot sizes: 3U (100 x 160 x 160 mm) and 6U (233 x 160 x 233 mm). 6U profiles offer more space, higher performance and additional interfaces compared to 3U profiles. 6U systems are more expensive and typically less common. 3U systems are compact, cheaper, more energy-efficient and ideal for mobile platforms.

Figure 1: OpenVPX describes different slot profile types. (Figure: VITA)

Backplanes: To enable communication between the various modules, they are connected to each other via so-called backplanes. The developer can choose from various topologies, each of which supports a different data rate. An OpenVPX Backplane Profile is a physical definition of a backplane implementation that includes details such as the number and type of slots that are implemented and the topologies used to interconnect them. Ultimately a Backplane Profile is a description of Channels and Buses that interconnect slots and other physical entities in a backplane. Profile Parameters are used to further describe properties of a Backplane Profile.

Pipes: OpenVPX Pipes are a physical aggregation of differential pairs used for a common function that is characterised in terms of the total number of differential pairs. A Pipe is not characterised by the protocol used on it. The following Pipes are predefined by OpenVPX:

  • Ultra-Thin Pipe (UTP) 2x pairs
  • Thin Pipe (TP) 4x pairs
  • Fat Pipe (FP) 8x pairs
  • Double Fat Pipe (DFP) 16x pairs
  • Quad Fat Pipe (QFP) 32x pairs
  • Octal Fat Pipe (OFP) 64x pairs

Cooling: OpenVPX supports numerous cooling schemes.  These are used mainly in military and aerospace applications where convection cooling cannot be used. These allow heat to conduct through the printed circuit board or through a conduction plate or channels on the module. Expanding wedge locks then transfer the heat out to the chassis through wide slots cut into the metal chassis sidewalls. Multiple cooling methods are defined in the VITA 48 standards.

  • Standard Air Cooled
  • Air Flow Thru
  • Air Flow-By
  • Conduction Cooling
  • Liquid Cooling
  • Liquid Flow Thru

Figure 2: Liquid Flow Through Cooling. (Figure: VITA)

Design Considerations with the OpenVPX Architecture

Having reviewed all the components that can be used to design OpenVPX applications, it is important to address important design hurdles. At the start of the project, developers should determine what they want to focus on in the design, for example robustness, energy efficiency or extensive interfaces. When ratifying the standard, VITA exhausted various options that developers should be aware of to make the right decisions at an early stage.

This includes, among other things:

Power supply (VITA 62):

  • How much power do I need for my application?
  • Which power supply module is suitable?
  • Which backplane topology do I need for this?
  • Do I need redundancy?

Cooling (VITA 48):

  • Conduction Cooling (VITA 48.2): Here, the heat is dissipated directly from the module to the chassis via the backplane slot.
  • Air Flow Cooling (VITA 48.1): This method uses air flow to cool the modules by arranging the modules so that air flows through the chassis and dissipates the heat generated.
  • Liquid Flow Through (VITA 48.3): Liquid cooling, a specialized cooling technology that uses liquid to dissipate heat, often in applications that require very-high-power densities.

 

Further considerations, as already described, concern the backplane design, signal routing and the choice of interfaces. The OpenVPX standard (VITA 65) specifies various protocols that are used for communication between the modules and for data transmission within an OpenVPX system. These protocols are crucial in determining the data rate, flexibility and compatibility of OpenVPX systems. There are different categories of protocols that are suitable for different use cases and requirements, for example:

  • PCI Express (PCIe)
  • Serial RapidIO (SRIO)
  • 10/40/100 Gigabit Ethernet (GbE)
  • InfiniBand
  • Fibre Channel
  • VME-Bus
  • Serial ATA (SATA)
  • AURORA
  • Serial Attached SCSI (SAS)

Finally, ensure that the selected backplane supports the slot profiles of the modules selected for the specific application.

 

5 Tips for Correct Component Choice

Now you know the biggest challenges when designing OpenVPX applications and can use our considerations to select the best modules for your application. However, in order not to lose track of all the considerations, we would like to give you 5 tips.

  1. Choose robust, MIL-STD-conforming modules
  2. Use the right Backplane Topology for real-time communication
  3. Use modular and scalable systems for future requirements
  4. Be aware of cybersecurity and system monitoring
  5. Use AI and field programmable gate array (FPGA) accelerators for edge AI or autonomous systems

 

Meet the Requirements with Etion Create

To meet all these requirements for modern and future-proof defence applications, the partner companies Sundance and Etion Create offer a broad product portfolio of different OpenVPX modules.

 

The VF365 is a 3U OpenVPX module that leverages Altera Arria® 10 system-on-chip (SoC) FPGA and Texas Instruments KeyStone® Multicore digital signal processor (DSP) technology to provide an ultra-high bandwidth processing platform, ideally suited for computation and bandwidth-intensive applications such as radar, signals intelligence (SIGINT), electronic warfare (EW), software-defined radio (SDR), and real-time video processing.

Figure 3: The VF365 is a 3U OpenVPX module. (Figure: Etion Create)

Another possibility is to use the VF370, which is a 3U OpenVPX Single Board Computer (SBC) module that utilises the Intel Atom® E3900 series of embedded processors, Altera Cyclone® V FPGA technology and a FMC mezzanine site to provide a module with scalable processing power and flexible IO options for reduced Size, Weight and Power (SWaP) applications. It is available in standard air-cooled and rugged conduction-cooled versions.

Figure 4: The VF370 which is a 3U OpenVPX Single Board Computer (SBC) module. (Figure: Etion Create)

Developers can rely on the Sundance and Etion Create portfolio because it offers high-performance, SWaP-optimized OpenVPX modules with state-of-the-art FPGA, RISC-V and AI accelerators specifically designed for demanding real-time and edge computing applications.

They also provide software and firmware (FPGA) design services on module and system level.

Close adherence to VITA and SOSA standards ensures maximum interoperability, long-term availability and easy system upgrades. Through continuous innovation and technology partnerships, both companies provide robust, future-proof solutions for aerospace, defence and autonomous systems.

 

Learn more about the Sundance Etion Create portfolio on our website.