The highly competitive nature of the electronics market has made it absolutely essential to hit the target window of opportunity with product releases. Being second or third to enter the market with a new product can result in greatly reduced sales or a cancelled program. Manufacturers cannot afford to apply limited engineering resources to failed product development efforts. Reducing the design cycle has become a mandate in every step of the new product development process.

Rather than design a new system from a blank sheet of paper, engineers are choosing to utilize embedded computers in a wide array of products. Embedded or single-board computers are self-contained computing devices that are designed to control the functions of the equipment into which they are integrated. Unlike the common PC, which is considered a general purpose computer, embedded computers are more narrowly focused on performing specific functions for its host. Embedded computer systems can be found in everything from hand-held inventory scanners to advanced military aircraft. Applications are expanding in industrial automation and control, networking and storage, security, robotics, transportation, wireless communications/telecommunications, test and measurement, Internet, medical, military and aerospace markets. They can be purchased from a wide variety of commercial vendors and can be tailored to meet the requirements of many diverse applications. Rather than design a special purpose custom computer for each new product, engineers are able to select an off-the-shelf embedded computer module that can incorporate a huge variety of processors, operating systems, memory options, and I/O; allowing the designer to concentrate their internal engineering resources on development of the final product. Embedded computers are utilized not only during the product development process, but often are carried into volume production of the final product. Suppliers of embedded computers can often offer their product less expensively than if the OEM were to build the board internally.

Embedded computers are often connector intensive, as they typically require communication and power from external sources. An embedded computer may be utilized in many different products, making connection flexibility a key attribute of the unit. Connectors associated with embedded computers fall into two categories; Level 2-3 (internal interconnects) and Level 6 (I/O).

A typical embedded computer may include a variety of connectors. In some cases, the unit may consist of a single PCB, while others utilize a secondary mezzanine board typically for I/O, memory, or placement of the processor.

The computer-on-module is a complete CPU engine added to a carrier board and is used where backplane architecture is not practical.

Embedded computers by nature must be adaptable and offer connectivity options to serve a wide variety of applications and environments. The form factor of embedded computers can range from tiny computer-on-modules attached to a carrier board, to an enclosed box assembly complete with power supply and I/O.

Suppliers of embedded computers strive to make utilization of their products as simple as possible, making industry standard connectors preferable, especially in I/O applications. Connectors such as RJ-45 Ethernet connectors, RS-232 D-subminiature connectors, and square posted headers/receptacles, for power and auxiliary signals, are very common.

Industrial control applications often require communication to remote sensors via discrete wire, making terminal block connection to the PCB a requirement. Wires can be installed in the field without the use of special crimp and insertion tools.   The physically small size of the imbedded computer can become a limiting factor in its ability to provide sufficient space for I/O connectors. Some suppliers have made extraordinary efforts to solve this challenge by providing external I/O cables.

Connectors used internally to the embedded computer itself may or may not utilize standardized interfaces. Manufacturers may choose a mezzanine connector based on its ability to fit the available space and also to provide sufficient high-speed performance. If a processor is socketed, the chip supplier often dictates the selection of connector.

Embedded computers, based on an industry-wide open standard, can stimulate innovation while creating a competitive and broadly-based market.

A classic example of an embedded computer standard is the PC/104. An industry consortium controls both the form factor and computer bus structure, making this an attractive option, especially in harsh environment applications. This concept is built around unique stacking functional modules to create scalable, application-ready computer platforms.

Each standardized board carries the same stacking connector in a defined area, allowing multiple boards to be manufactured by a variety of sources, and to mechanically stack and electrically function together.

The Standard PC-104 uses a 104-position connector for the ISA bus interconnect. Subsequent updates of this standard have resulted in the PC/104-Plus, which added an additional 120-pin connector for the PCI bus. The latest iteration of the PCI-104 platform retains only the PCI connector.

In a continuing effort to keep the PC/104 architecture viable, a need for a larger format board was identified and resulted in the EPIC (Embedded Platform for Industrial Computing) specification, which was released in March of 2004. EPIC boards support both PC/104 and PC/104-Plus and were formally adopted by the PC/104 Consortium in early 2005. The size of this board (29.4 square inches) is about halfway between the original PC/104 (13.5 square inches) and the EBX (Embedded Board eXpandable) (46 square inches). These boards offer the necessary PCB real estate to support all of the necessary components for a full-function embedded computer.

EPIC Express is the latest step in the PC/104 evolution, and is the merger of the EPIC board form factor with the high-speed serial signaling of PCI Express. The objective of a group consisting of five industry leaders is to retain support for legacy I/O while expanding the bandwidth of the system with switch fabric architectures.

The .100” centerline ISA connectors are retained, but the 2mm PCI bus connector has been replaced by one or three 28-position high-speed surface mounted connectors that have been optimized for low voltage differential signaling.

Demand for greater bandwidth and system functionality continues to spur the development of new embedded form factors.

Embedded Technology Extended (ETX) is focused on the implementation of embedded CPU modules attached to custom baseboards, also known as computer-on-modules (COM).

Connections between the baseboard and the module are via new COM Express 0.5mm centerline surface mount connectors. These low-profile connectors feature an external shield to support high-speed LVDS signaling.

Another emerging embedded module format is the XMC as a performance upgrade to the aging PCI mezzanine card (PMC) standard. As has been the case with several other evolutionary advances in existing protocols, XMC provides a clear migration path to higher performance, while achieving a fabric agnostic design. The specified connector is a low-profile 114-position interface that handles all of the differential serial fabric switched signals.

The physical implementation of XMC cards utilizes a unique mix of the standard PMC mezzanine card connector set, plus one or two of the new high-speed interfaces.
 

XMC modules are expected to find applications in military and avionics equipment.

Bishop & Associates Comments:

• The popularity of embedded computers is increasing, as pressure to bring new products to market with limited engineering resources has become the accepted norm.
• Embedded computer modules typically include a great variety of separable interconnects to facilitate both internal and I/O communication needs.
• The evolution toward high-speed differential bus structures has generated the need for high- density/high-speed connectors that can fit in the required form factor.
• The entire market for embedded/single-board computers based on open industry standards is creating highly competitive markets for innovative new products and their specified connector interfaces.
• Forward and backward hardware compatibility is a highly attractive attribute as legacy embedded computer platforms evolve to next-generation performance.
• Market growth in the mezzanine card connector segment is being driven in part by the increased interest in embedded computer architecture.

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, Chandler, Ariz. 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.