Rewriting the book on COMs: ruggedized and standardized - Embedded.com

Rewriting the book on COMs: ruggedized and standardized

In the embedded systems community, there is a continual drive to increase system performance and design efficiency to make embedded technologies more affordable, and more useful in a greater number of applications.

The road to innovation in embedded computing usually starts with a new technology that promises to save time, money, and development efforts. Next is the rush to bring new products based on these technologies to market.

But many designers know the sad side of this tale all too well; that these products are brought to market before the industry, as a whole, has been able to grasp the concept and implement it effectively.

While embracing new technologies is paramount to innovation, what are we left when each company tweaks the technology to fit its own specifications – either for convenience or expedience?

This doesn’t help the end user, who will probably need to wade through incompatibility issues among different components or will be forced into a single-supplier situation.

And it isn’t very beneficial for the manufacturers either, as they are left with frustrated customers who may be reluctant to turn to them when the next technology evolution occurs.

One way around incompatibility in the market is standards organizations that seek to:

  • Promote a universal platform on which developers can base systems that talk effectively with one another;
  • Ensure components work side-by-side in a system, not against one another; and
  • Foster a community of developers and manufacturers that work together for the growth of the industry as a whole.

For the embedded community, VITA has long promoted open system architectures of real-time, modular critical embedded computing systems. One of the standards on track for ratification in 2013 is VITA 59 RSE (Rugged System-On-Module Express), which holds many answers embedded designers are seeking in terms of a compact format, an industry standard platform, and rugged performance.

Based upon the PICMG COM.0 standard, VITA 59 not only capitalizes on the small form factor and interchangeable concepts behind this original standard, but adds ruggedization and modern serial interfaces while defining pin-out for compatibility among different modules, regardless of manufacturer.

COMs
A Computer-On-Module (COM) is a complete computer on a plug-on module that offers many benefits. Because the I/O is configured on an individual carrier board, the system designer can tailor the functionality to the application, save development costs, and shorten time-to-market, all primary goals for an embedded designer.

Since CPU functions can easily be standardized for many fields of use, COMs-based systems can use a more or less standard plug-on CPU module. Even complex CPUs, including those with multicore technology, can be realized on a compact, highly-integrated COM.

Special I/O interfaces, memory devices, connectors or form factors may be added to the carrier board. Also, FPGA-based functions can be added to a carrier board or to the CPU module, if desired.

All this makes the electronics 100% tailored to the application, and future-safe. The implementation is far less complex and less expensive than reengineering a system from scratch, especially in applications where a special I/O platform is needed. The CPU module, which provides a standard interface to the carrier, remains scalable and can be used in a design application much like an integrated circuit component.

Two major downsides that have hindered the wide-spread use of COMs, however, are the lack of ruggedization and the disparity among the structure of the modules.

The soon-to-be-ratified VITA 59 RSE is based upon the concepts presented in the ESMexpress architecture. VITA 59 formalizes ESMexpress into a standard that ensures component compatibility, easier upgrade paths, and faster time to market.ESMexpress utilizes the same 125 mm x 95 mm board size as the previousCOM Express form factor. Both ESMexpress and COM Express provide theadvantages of the original COMs that implement CPU functionality on astandardized module and let unique application requirements – such asI/O interfaces, extra memory devices, and connectors – be handled by thecarrier card.

While both executions of the COM approach adhereto a formal industry standard for true interchangeability amongcomponents, only the VITA 59 standard governing ESMexpress addresses thebenefits of rugged performance in multiple areas such as connectors,operating temperatures, shock resistance, and EMC protection.

ESMexpressnot only allocates specific tasks to the CPU module versus the carrierboard, but also incorporates a resource-sharing concept of usingavailable IP cores to configure field-programmable gate arrays on thecarrier board to enhance specific functionality. The fixed assignment ofthe processor and the SDRAM functions on the CPU module eliminates theneed for complex and expensive changes to that unit. Conversely,licensing IP cores to execute specific I/O requirements through carrierboard FPGAs is a quicker and more affordable way to adapt to customapplication inputs. Using FPGAs also allows more I/O to be achieved inless space – an important consideration for small form factorapplications.

Regardless of the microprocessor platform selectedfor an ESMexpress CPU module or any other customized attributes of thecarrier board, the VITA 59 RSE standard includes a list of attributesfor rugged performance in harsh operating environments:

Connectors.  Thepin assignment on all ESMexpress CPU modules is fixed to guaranteeinterchangeability with any carrier board that meets the VITA 59standard.

Electrical signals from the module board aredistributed on two robust 120-pin connectors on the board’s bottom side,a design that has been approved by major railway and avionicscompanies.

The connections are defined only for high-speedmodern serial buses such as PCI Express, Gigabit Ethernet, USB, SATA,SDVO, LVDS, HD audio, and several utility signals as well as a single 12V power supply.

Cooling. While heat build-up is afunction of processing power, several factors in the ESMexpress solutionhelp alleviate cooling concerns in compact spaces or extreme ambienttemperatures. For example, carrier modules with low-voltage chipsminimize heat generation, even at processing speeds up to 1.6 GHz.

Moreimportant, however, is that the mechanical configuration and thecombined conduction/convection cooling considerations of the VITA 59design accommodate functional operating temperatures ranging from -55°Cto +125°C. What makes that possible is the built-in heat transferproperties of the CPU module design, the choice of connector, and thesolid connections between the chip, the module frame and cover, and thecarrier board.

Heat from the CPU is transferred to the metallictop cover and then to six cooling tabs that mate with the module framefor conductive cooling. Supplemental cooling is also possible byapplying a heat sink to the top of the module cover.

Environmental durability. Robust connectors, soldered components, and the solid mechanicalconnections that facilitate convection cooling also enable ESMexpressmodules and carrier boards to withstand substantial shock up to 15 g/11ms and sinusoidal vibration of 1 g/10 Hz to 150 Hz.

Theavailability of conformal coating when needed enhances the module’sability to withstand harsh, wet, or chemical-laden environments. Sowhether end-use applications are in external or mobile applications orin a harsh industrial environment, VITA 59-compliant solutions offergreater robustness than other small form factor COM designs.

EMC protection. The 100% sealed metal housing design of the ESMexpress module alsoprovides exceptional EMC protection, conforming to EN 55022 for radiodisturbance, to EN 55024 and EN 61000-4-2 for electrostatic discharge,and EN 55024 and EN 61000-4-4 for burst.

Conclusion
Withinthe parameters of the VITA 59 RSE standard, the possibilities forESMexpress implementation are extensive. Compact form factors make foran attractive resource for space-constrained applications in fixed ormobile computing environments. Rugged design and constructioncharacteristics open up the versatility of the COMs concept to a widerrange of applications than ever before:

  • Signal, control, or passenger information systems in railway applications
  • Industrial robotic applications, from plastics production to semiconductor clean-room production and general automation
  • Extreme industrial environments
  • Demanding mobile computing needs such as medical equipment or transportation applications

Thebroad range of high-speed serial interfaces – from USB and SATA toEthernet and PCI Express – plus the versatility of FPGA customizationprovides cost-effective adaptation to a wide range of computingenvironment needs.

As with the COM Express standard, ESMexpressfeatures interchangeable CPU modules and carrier boards that offer endusers flexibility to mix and match the ideal elements from differentmanufacturers as they adopt the finalized VITA 59 standard.

Barbara Schmitz has served as Chief Marketing Officer of MEN Mikro Elektronik. Shegraduated from the University of Erlangen-Nürnberg. Later, she studiedbusiness economics in a correspondence course at the Bad Harzburgbusiness school and followed an apprenticeship in Marketing andCommunications in Nuremberg.

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