Rugged COM technology ascends to new lows

Computers-On-Module (COMs) have already penetrated a sizable portion of the medical device market along with slot machines, industrial automation, and various network-communication applications. The recent embedded world show in Germany revealed a clear trend toward cost-optimized COMs using gold-plated card edge connectors that plug into cheap consumer memory-style connectors. Although these devices may fit in mainstream, fixed-location commodity applications, they don’t meet the demands of portable system manufacturers who need rugged, gas-tight mating connectors between their various boards.

The Small Form Factor Special Interest Group (SFF-SIG), a trade group that focuses on rugged and reliable embedded technologies rather than consumer and enterprise markets, formed a working group to fill this need. The group found that a board-to-board connector pair was needed in order to meet stringent requirements for shock, vibration, temperature, dust, corrosion, and the ever-denser computing needs of military display terminals, soldier-wearable computers, and commercial fleet vehicles. Board-to-board mated connectors – designed for high reliability and harsh environments – have substantial connector wiping during insertion and strong retention forces. The end result is a rugged-by-design module standard called CoreExpress.

Minuscule mezzanine module

A COM and carrier combo is the new popular approach to optimized custom small form factor system designs. Think of CoreExpress as a tiny mezzanine CPU module that mounts parallel to the main board or carrier board. At smaller than the size of a credit card, the 58 mm x 65 mm CoreExpress module is among the smallest open-standard form factors for x86 processors. The two boards are joined via four mounting holes, screws, and standoffs.

The CoreExpress specification uses Tyco board-to-board connectors for all signals that pass from the processor module to the custom carrier board. CoreExpress even goes a step further as a purely digital module, reserving Ethernet PHY on the carrier board so that analog signals do not go through the additional set of connectors, unlike other COM standards. The SFF-SIG prefers to keep digital harmonics away from sensitive analog circuits.

Low-power, x86-based assurance

Intel processors are often favored for long life cycle and wide temperature operation. The Atom E620T is the current entry point for basic display and system-control processing, at 600 MHz with a -40 ºC to +85 ºC operating temperature range. Another obvious direction in the board space is the use of ARM processors; however, x86 Operating Systems (OSs), device drivers, and tools are still more familiar and time-tested than their ARM counterparts among OEM board users.

Many new COMs are available with only 1 GB or 2 GB RAM. CoreExpress modules also offer a lower entry point of 512 MB for basic control applications. The Atom E6xx platform provides one USB client port in addition to six USB host ports. This client port is well-suited for mobile applications. A Controller Area Network (CAN) port is useful in factory environments as well as in military and commercial vehicles, and is even used in some medical devices. LVDS provides a basic LCD interface for up to 1,280 x 768 pixel resolution, while PCI Express, SATA, and LPC bus round out the CoreExpress module feature set.

The race to capture the burgeoning consumer tablet market has certainly benefitted embedded designers, giving them broader processor choices, but the latest generations of these tend to go overboard with power-hungry graphics to play streaming video. CoreExpress uses restraint and aims squarely at basic Linux and Windows applications for tiny rugged applications instead. ADLINK (Taiwan and U.S.) and Syslogic (Switzerland) are both providing Atom E6xx-based CoreExpress modules that meet these stringent specifications.

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Figure 1: ADLINK’s CoreExpress-ECO2 module drives power consumption below 5 W.
(Click graphic to zoom by 1.3x)

COM technology has advanced to new lows – smaller size, lower power, lighter weight, lower analog-digital noise coupling – all with less bending during shock and vibration loads. Atom-based modules like the one shown in Figure 1 are already available and have been tested in demanding applications. Unlike with most other trade organizations, SFF-SIG specifications like CoreExpress can be downloaded for free and without providing contact information. Download today or browse other specifications at www.sff-sig.org.

Small Form Factor Special Interest Group 408-480-7900 info@sff-sig.org