Single Board Computers in the Arm World

Why longer lifetime programs in mil/aero, industrial, and smart city infrastructure applications have reason to notice the arrival of extreme temperature and rugged Arm-based SBCs

Acorn Computers, now known as Arm Limited, first deployed the Acorn reduced instruction set computing (RISC) architecture in the BBC Micro computer in 1981. Since then Arm processors have gone through many iterations and have become widely used in mobile and consumer electronics applications. However, smart city, mil/aero, and industrial applications demand embedded computing solutions that are more production-ready, rugged, and tolerant of extreme temperatures. This article describes the various ways to deliver Arm-based processing capability: System on Chip (SOC), System on Module (SOM), and complete Single Board Computers (SBC). The article concludes with a focus on the SBC approach, describing a practical example, and its benefits and applicability to specific applications.

Three Routes into Designs
In the embedded computing market, Arm-based designs are a distant second to products based on x86 architecture. But with Arm processors evolving into more capable and higher performance units, their use in embedded applications is expected to grow at approximately twice the rate of x86-based solutions near term. Various sources predict this growth will be due to the application of Arm-based solutions in automobiles, sensors, IoT, unmanned vehicles, and other embedded applications. This is based on power and cost advantages. Whether based on Arm, or on x86 technology, computing architecture finds its way into designs via three routes: as a SOC, SOM, and integrated into an SBC.

As the SOC name suggests, a system on a chip is comprised of more than just a processor. The chip may contain processor core(s), memory, clocks, and I/O interfaces such as USB, Ethernet, and others. The advantage of this degree of integration is small size and, in the case of Arm-based SOCs, low power consumption, making them ideal for small devices such as smartphones, where a high degree of miniaturization is valued over flexibility and a multitude of external interface types. Of course, the down-side of using a system on a chip is that you get whatever is in the chip; the parts that match your needs, and the parts that don’t. However little or however much the designer put into the chip, that is what you have to work with, and what you pay for. Figure 1 shows conceptually the internal functions of an Arm SOC.

Figure 1:  Overview of a system on a chip.

A system on module (SOM) adds more flexibility by mounting the SOC on a board and expanding it with the desired memory or I/O interfaces. A SOM approach allows more specialized boards to be built, with larger memory, a greater number of I/O channels, or specific types of I/O that an application requires. Even though some additional functions and signals are included on these boards, they are only “modules,” which are not ready to connect to the outside world. SOMs are primarily CPU-centric products that are meant to act as only one part of an embedded computer. Figure 2 shows an example of a SOM.

Figure 2:  Example of a System on Module showing a COM Type 10 connector on the bottom side, which is used to connect to a carrier board.

A carrier board is necessary to convert the raw processor and I/O signals to standard I/O signals and real-world connectors such as Ethernet, DisplayPort, HDMI, USB, SATA, etc. However, a SOM provides a convenient head-start for someone designing their own system. For someone requiring a ready-to-go solution, a companion carrier board will be required. A SOM and carrier board set is shown in Figure 3.

Figure 3:  Example of a board set. The connectorized carrier board is on the top, and the system on a module is underneath.

The last category, Single Board Computers, is quite different from SOCs or SOMs. SBCs do not require additional carrier cards, companion boards, connector break-out boards, or other add-ons to function. They are ready to turn on and run application software. Although SBCs are quite common in the x86 world, they have traditionally been less available in Arm-based products. Fortunately, this is changing. As Arm processors become more powerful, and now include video output and other important I/O features, the availability of Arm-based SBCs is on the rise.

As an example, Figure 4 shows the Tetra SBC from VersaLogic Corp. This SBC is based on the i.MX6 quad-core processor.

Even though it’s a compact SBC, the Tetra model in this example does not sacrifice capabilities to get there. It includes Gigabit Ethernet, USB ports, SATA, HDMI, CAN, MIPI camera input, serial I/O, and audio I/O. There is even a 6-axis e-compass option for use in motion sensitive applications such as unmanned vehicles.

Figure 4: “Tetra” quad-core Arm-based SBC.

Applications Are Changing, Too
Applications for Arm-based single board computers are changing as well. Boards like the Tetra and the smaller Zebra board have been designed from the ground up for challenging embedded applications. They meet the demanding requirements of industrial and mil/aero applications including extended temperature operation (-40 to +85◦ C) and MIL-STD shock and vibration standards. Even in less demanding applications, such as parking garage sensors or smart meters, there is a need to operate over a wide temperature range, especially inside a sealed box. As the “smart city” concept grows, applications for this type of solution will increasingly require these types of cost effective, rugged, single board computers to provide computing power where it is needed.

Figure 5: VersaLogic’s Zebra SBC is  a smaller-size SBC (95 x 95 mm) with single and dual-core processor options. It includes industry standard I/O ports and supports full -40 to +85◦C operation.

In summary, users have access to Arm computing capability via system on chip, system on module, and single board computer offerings. The SBC route provides an off-the-shelf production-ready option. For OEMs this cuts six to twelve months from the product design schedule versus having to design custom I/O and expansion solutions around SOCs or SOMs. SBCs allow the design team to focus on development of the application rather than the computer board. The advent of extreme temperature and rugged Arm-based SBCs expands their applicability and, when coupled with long product lifecycles, makes them an attractive solution for longer lifetime programs in mil/aero, industrial, and smart city infrastructure applications.

Bob Buxton is Product Manager, VersaLogic Corporation, Tualatin, Oregon

Bob Buxton brings more than twenty years of experience in both R&D and product management roles. He has worked within, and has provided products to, the mil/aero segment. His R&D experiences have been primarily in connection with radar and microwave sub-system design.

He is currently working in product management at VersaLogic Corporation, a leading provider of embedded computers which are designed for the most demanding applications. VersaLogic is located in Tualatin, Oregon.

Bob holds a master’s degree in Microwaves and Modern Optics from University College, London and an MBA from George Fox University, Newberg Oregon. He is a Chartered Engineer and a Member of the Institution of Engineering and Technology.



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