Embedded Computer Standards Proliferating
By Bob Hult, Bishop & Associates Inc.

The embedded computer automates a wide variety of devices, from the mundane to the exotic. Rather than design a custom device from scratch to satisfy a new application, an off-the-shelf embedded computer in a variety of form factors can be quickly and economically adapted to many tasks.

Diverse applications in data acquisition, banking, digital imaging, network security, military, transportation, aviation, medical instrumentation, power management, telecom, gaming, factory automation, surveillance, and access control take advantage of embedded computing devices.

The typical car, for instance, now contains many embedded computers that manage everything from combustion to skid control.

The instrument cluster and even the steering wheel are now outfitted with embedded computers with touch screen interfaces that enhance both the safety and comfort of the driver.

Embedded computers differ from general purpose computers in a variety of ways. Unlike a typical personal computer, embedded computers are dedicated to a limited number of functions. Embedded computers in industrial and military applications require environmental resistance, durability, and reliability far in excess of the typical multi-purpose computer. Programs are much smaller and typically stored on solid-state memory, rather than on a hard disk drive. They are designed to support Windows, as well as Linux and Mac operating systems, using a variety of processor and double data rate (DDR), or flash memory, chips.

Another characteristic of embedded computers is that they are often physically smaller than the normal PC, which is an advantage when they are integrated into the potentially-limited space available within a larger device. Custom functions, such as I/O or memory, may be added by use of an optional mezzanine card. Embedded computers are available in a variety of form factors, including single board, daughtercard, stacking, and computer-on-module, each of which has found its own niche applications. Daughtercard versions may include a mezzanine card that can adapt the computer to a specific I/O. Computer-on-modules (COM) are often added to a generic host board to create a custom configuration.

A typical embedded computer offers a wide variety of standard input/output protocols, including USB, CAN, VGA, RS-232, Ethernet, and SATA/SAS. Many of these define a specific connector. The need for flexibility makes the inclusion of separable interfaces a critical attribute of embedded computers.

Adding a standard power connector, removable memory socket, processor sockets, display interfaces, and mezzanine and/or daughtercard connectors often makes the typical embedded computer a showcase of electrical interfaces.

The key to wide adoption of embedded computers is their ability to be easily adapted to perform in a host of applications. The good news is that the availability of embedded computers in a standardized format allows designers to select a form factor, degree of computing power, level of reliability, and price point that closely matches the diverse requirements of specific applications. They are appearing in more applications because they offer greatly reduced design cycle times, a critical attribute in this period of limited development resources and demand for quick return on investment, with reduced risk.

A variety of commercial mezzanine card manufacturers offer embedded computers in standardized form factors that allow rapid adaptation in many different applications.

Embedded computers range from tiny devices that can continuously monitor and adjust the comfort of a running shoe, to large VPX backplanes designed for advanced military applications.

A continuing stream of open standards has evolved over the years that address new application requirements, as well as incorporate advanced technology. Typical embedded computer standards define the mechanical form factor and the type and location of electrical interfaces. The specific function of the board is a blank sheet on which the board developer is allowed to add their innovation. The adoption of high-speed serial buses to replace parallel bus structures spawned an entirely new series of updated platforms. Many of the legacy standards maintain backward compatibility to ease the transition to new technology.

The bad news is that the proliferation of new competitive standards has evolved, resulting in an alphabet soup of competing standards driven by an expanding galaxy of formal standards’ writing organizations, consortiums, special interest groups, and individual embedded computer makers. The proliferation of industry-recognized specifications has somewhat diluted the advantages of using an industry standard, and has resulted in a highly fragmented market.

One of the earliest versions of an embedded computer platform is the venerable PC/104, which was developed with the goal to adapt the ease and cost advantages of personal computing technology to embedded applications.

Created in 1992, PC/104 remains one of the most common standard platforms in the industry today. The standard is based on 3.6-inch X 3.8-inch modular boards that vertically stack via specific connectors in defined locations. A user is able to select from a series of standard functional blocks to assemble a custom configuration.

PC-104 has remained relevant by constantly adapting to the introduction of new technology. Originally conceived with an ISA bus, PC-104-Plus added a second connector for a PCI bus that provided 8-, 16-, and 32-bit bus capability.

In an effort to address new applications that required more printed circuit board space, the EPIC (Embedded Platform for Industrial Computing) was introduced. Specific zones on the larger card are defined by the specification.

The Embedded Board Expandable (EBX) specification attempted to maintain a compact form factor, while allowing the use of higher performance processors. The stacking connectors remained the same to insure backward compatibility. Connectors are available from a global array of suppliers.

PCI/104-Express and PCIe/104 maintains the EPIC form factor, while adding PCI Express technology. Samtec’s three-bank stacking connector supports a high-speed bus structure.

Another approach at delivering a highly-flexible embedded computing system is the PCI Industrial Computer Manufacturers Group Computer-on-Module (COM) Express™ specification. A carrier or baseboard is configured to address the requirements of a specific application. A CPU module mounted on a mezzanine card provides the core computing functionality of the system.

The Com Express specification defines the separable interface between the baseboard and COM module as one or two, 220-position Tyco Electronics FH-type surface-mounted connectors.

These connectors are rated to 3.125 Gb/s, and provide a rugged and reliable interface.

Embedded Technology Extended (ETX) utilizes a 3.7-inch X 4.9-inch COM form factor. Two Hirose FX-8 100-position mezzanine connectors provide the connection between the baseboard and the processor-mounted module.

The high-performance computing and military market segments are also experiencing the transition from bus-based to switched-fabric systems. The VITA 42 XMC specification provides a performance migration path from the PCI mezzanine card (PMC) to support next-generation performance requirements.

 

In addition to the standard PMC mezzanine connectors, one or two new low-profile 114-position connectors from Samtec have been added to handle the high-speed channel interfaces.

New specifications continue to address emerging applications.

Field programmable gate arrays (FPGAs) have become a critical component of many embedded computers, with their ability to allow flexible programming and software updates after installation. VITA has created a new standard—VITA 57, that defines a mezzanine module designed specifically for FPGA-based systems. VITA 57 boards are half the size of a standard PMC mezzanine card, which offers a smaller footprint and lower cost.

 

MicroTCA is another format that has been recognized as an ideal embedded platform in low-cost communications, as well as military Commercial Off-the-Shelf (COTS) applications. The defined interface for this mini-backplane system is a dual-row, 170-position edge connector.

The small Form Factor Special Interest Group (SIG) has entered the fray with the SUMIT and COMIT form factors for embedded computers.

Boards that conform to the Stackable Unified Module Interconnect Technology (SUMIT) specification feature multiple lanes of PCIe and USB interfaces, as well as ExpressCard. In addition to the standard PC/104 connector, two Samtec stacking Q2 Series connectors handle the high-speed connections. The Pico-ITX is a subset of SUMIT, which addresses smaller requirements for smaller form factors.

The new Computer-on-Module Interconnect Technology (COMIT) specification is not yet released, but is expected to be capable of supporting higher speed communication channels, including PCI Express Gen2, Ethernet, SATA, VGA, and USB3. It is targeted for small processor modules such as the new low-power Intel Atom and VIA NANO. The exceptionally low power demands of these processors will allow the automation of entirely new classes of equipment that can operate at remote locations on small batteries or solar panels. COMIT modules will utilize 240-position Samtec SeaRay™ connectors.

Even individual embedded computer manufacturers are introducing new specifications. Micro/sys has begun marketing a stackable module combining the familiar PC/104 or EPIC form factor with USB 2.0 communication protocols to provide a module with high-performance at low cost. Up to 16 boards can be stacked without the use of bulky USB cables. Stackable USB boards utilize Samtec Q2 surface-mount connectors.

Connector manufacturers will benefit from the expansion of the embedded computing market. Select suppliers, such as Samtec, have established a reputation for offering a wide variety of stacking connectors. As new embedded form factors have been developed, existing or slightly modified connectors from Samtec and other connector manufacturers have become the logical choice in the specification. As a result, Samtec has evolved from a custom-niche connector supplier to a major source of standardized interfaces that support the embedded computer market. Their website features a very useful industry standard and development platform tab that allows a designer to quickly determine the defined connector by specification, and gather technical, as well as price and delivery, information.
 

The proliferation of new form factors is likely to continue as new applications for embedded computers expand. Developing low-profile, high-density, high-speed mezzanine connectors will continue to be an enabling technology in new embedded computers that must survive challenging environments, ranging from unmanned weapons platforms to a teenager’s bedroom.

Bishop & Associates Comments:

• Embedded computers are appearing in an expanding array of applications because they can reduce design costs as well as cycle time.

• Embedded computers represent an excellent market for a wide variety of electrical connectors that range from simple 0.025-inch post strips to high-performance stacking interfaces.

• A host of industry standards has emerged that allows designers to choose high-speed/high-density baseboard and pluggable modules available from a wide variety of suppliers. Competition among suppliers assures a constant stream of innovation, as well as market-driven prices.

• The proliferation of embedded computing platform standards has been a hallmark of this industry, and presents many packaging choices, but potentially less plug compatibility within the industry.

• Manufacturers of embedded computers offer a variety of off-the-shelf modules, as well as the ability to design and build custom assemblies on a standardized form factor.

• By the nature of the industry, embedded computers are typically a high-mix/low-volume market. New high-speed mezzanine connectors, defined by industry-accepted standards, may represent a niche market with better than average growth potential.

• Boards and modules that conform to a given standard assure the user of electrical and mechanical compatibility. Embedded computing applications tend to have a long service life, making a key objective of embedded computer users the long-term availability of selected modules.

• The objective of designing embedded computing systems that can be upgraded in the field is served well by pluggable mezzanine card architecture. New connectors that offer increased bandwidth and signal integrity support advanced current and evolving data rates.

• Legacy standards are constantly evolving to incorporate emerging technology, while often maintaining backward compatibility.

Robert Hult
Director of Product Technology, Bishop & Associates, Inc.
Robert Hult has been in the connector industry for more than 36 years. Hult began his career as a sales engineer for Amphenol. He joined AMP in 1972 and served in several management positions through 1996. In 1997, Hult joined Foxconn as group marketing manager for Intel in Chandler, Arizona, USA. Prior to joining Bishop & Associates, Hult was the regional application engineering manager for Tyco Electronics.

Hult graduated in 1968 from Bradley University with a Bachelor of Science degree in electronics technology and a minor in business.