Embedded Computers Connect to the World
By Bob Hult, Bishop & Associates Inc.

Computers have become an integral part of devices that range from weapons targeting systems to toasters. The ability to accurately measure conditions, calculate time, and control complex processes has revolutionized just about every electronic product we use today. Rather than design a custom computer to automate a specific piece of equipment, it often makes more sense to utilize an embedded computer, saving development costs as well as reducing the time to market. Embedded computers are found in a dizzying range of equipment categories, including process control, medical, materials handling, packaging, robotic, test and measurement, and food and beverage processing.

Embedded computers are typically dedicated to a relatively few specific tasks, allowing them to be smaller and more cost-effective than a general purpose computer. They start life much like a blank book, ready to be adapted to a specific application.

Since they are integrated into a vast array of applications, they are designed to be compatible with a variety of operating systems, including Windows and Linux, as well as a wide variety of output protocols. Their form factor varies from a single board, possibly with a stacked mezzanine card attachment, to rail-mounted boxes in industrial control applications. Customization through modularity and software allows the system integrator to adapt the basic embedded computer to meet the specific requirements of an application.

The need for flexibility often results in an embedded computer board with exceptionally high connector content. Embedded computers must be able to communicate with the outside world via industry standard interfaces, including USB, Firewire, Ethernet, VGA, DVI, RS-232 serial ports, mouse and keyboard DIN connectors, and even audio jacks.

Many applications incorporate industry-specific interfaces that shape the choices of I/O.

Single-board computers embedded in industrial control applications often use barrier block connectors, which require only a common screwdriver to install or remove discrete wires to the system.

An embedded computer will often be designed to include a BGA or LGA socket to accommodate a removable processor, as well as DDR2 and Compact Flash memory modules. Some boards may add the option of a PCI expansion daughtercard. Power is brought to the board via a variety of cable-to-board connectors. The result is often a product that looks much like a connector demonstration board.

Industry standards play a key role in the form factor as well as the connectivity of an embedded computer. The existence of these open standards has spawned a competitive market among suppliers, which are constantly introducing upgraded products to assure the user of forward and backward compatibility to the standard.

Several new generations of embedded computers have evolved to address higher performance, while entirely new platforms have been introduced over the past few years. The adoption of high-speed serial interconnects has resulted in a progression of new mezzanine connectors that enable next-generation equipment. PC-104 is a good example of how this evolution has influenced the connectors.

Created in 1992, PC-104 is one of the most common standard platforms in the industry, and was created to ease the adaptation of personal computer technology to embedded applications.

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 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 require 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.

 

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

Another approach that delivers 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 computer on module form factor. Two Hirose FX-8 100-position mezzanine connectors provide the connection between the baseboard and the processor-mounted module.

With the processor on this removable module, the baseboard can easily be upgraded by simply replacing the mezzanine card.

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.

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, which range 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 both design costs and cycle time.

• A host of industry standards have emerged that allow designers to chose baseboard and pluggable modules from a wide variety of suppliers. Competition among suppliers ensures a constant stream of innovation, as well as market-driven prices.

• Boards and modules that conform to a given standard assure the user of electrical and mechanical compatibility.

• The objective of designing systems that can be upgraded in the field is served well by pluggable mezzanine card architecture.

• 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.