Rich COM Express Options and SMARC Alternatives Add Complexity to Design Strategies

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Rich COM Express Options and SMARC Alternatives Add Complexity to Design Strategies

COM Express has a strong foothold in the realm of Computer-on-Module (COM) platforms due to the flexible, scalable design benefits it delivers. With three current form factors and a variety of pin-out options to define how the connectors are used, it’s more like a family of standards optimized for all levels of embedded performance in a small footprint.


Smaller footprints are in demand now to accommodate the landslide of portable devices, and to support systems that make up the Internet of Things (IoT) in the ever-expanding world of connected embedded applications. For developers competing in small form factor design, it is essential to understand current COM Express options as well as alternative standards such as Smart Mobility ARChitecture (SMARC) to select the most optimal small form factor platform for a given design.

Making Choices

COMs provide the chipset I/O to the carrier board via rugged board-to-board connectors. Associating module I/O designs onto the carrier board such as mPCI or mPCIe then allow a broad combination of I/O options that are readily available, and need only be brought into the design via the application-specific customization of the carrier board. LAN, SATA, video, audio, multiple USB or PCI Express ports are all available and depend simply on the requirements of the end-use application itself. COMs also integrate video processing and display, an important advantage for graphics-heavy imaging and data processing applications often found in connected, IoT systems.

After more than ten years on the market, COM Express capitalizes on platform advantages perhaps better than any other standard – offering many design options, each proven and supported by a well-defined worldwide ecosystem of providers and manufacturers. So, how do you select the right COM Express COM to best match your application requirements? The three form factors – basic, compact and mini – can be separated in terms of size, processor and thus performance Figure 1). The associated connector pin-out types are equally important to handle interfaces and manage signal processing requirements of the end-use application. Depending on performance levels required by the application, designers typically see a clear path to choosing the right COM Express COM. Applications leaning toward higher-end performance will require the space and processor performance enabled by basic and compact options, while space-constrained, battery-powered or portable platforms are suited to the mini.

Figure 1
COM Express modules typically have the same feature set but are differentiated by processor types, form factor and pin-out options.

COM Express Basic has the largest footprint at 95mm x 125mm, and is intended to handle applications that require more processing power. As such, basic incorporates higher-end processors such as Intel Core and AMD R-Series. Kontron and other manufacturers worldwide generally support COM Express basic with continued product releases that capitalize on the latest processor advancements. Graphics performance is frequently a key characteristic of applications that can use the processing power delivered with the basic form factor.  Examples of fitting deployments include high-end medical applications or industrial automation applications where visualization or communications requirements demand high compute power for data transmission.

COM Express Compact is the mid-sized form factor measuring 95mm x 95mm, and scalability is the key characteristic of the compact size. It incorporates processors ranging from Intel Atom and AMD G-Series all the way up to high performance Intel Core and AMD R-Series. The compact is also broadly used across embedded markets and enables OEMs to scale future product generations with processor upgrades, or release an entire product line at once using the same carrier board with different compute performance. For example, a compact form factor using an Intel Atom would be suitable for a low-end HMI in an industrial setting. OEMs could simultaneously implement an Intel Core using the same compact form factor and carrier board on another COM product, achieving performance suitable for a larger, high resolution display.

COM Express Mini, at 55mm x 84mm, is the smallest and is specifically geared toward handheld or battery-powered devices. In medical environments for example, COM Express mini would be used for handheld devices that are carried by doctors or portable systems used for mobile patient monitoring. These applications are typically manageable with less compute power but must also have reduced power dissipation to allow battery-based operation.

Pin-Out Types Further Define Usage

Originally five pin-outs were defined by the COM Express standard, providing a long-term foundation for signal assignment and design layout. COM Express 2.0 addressed the need for evolution, establishing Type 6 for extended graphics processing and Type 10 for performance in even smaller applications.  Type 6 and Type 10 are the most popular and widely used today.

Essentially based on Type 2, Type 6 is the most widely adopted COM Express pin-out type to date and is typically available in both basic and compact form factor COMs. Type 6 acknowledges the impact of graphics-based applications and better utilizes the expanded graphics possibilities of new processor families. Legacy PCI pins from Type 2 have been reallocated in Type 6 to support digital display interfaces and to enable additional PCI Express lanes. For example, if the application warrants PCIe x16 ports or an external graphics card, then Type 6 is required (Figure 2).

Figure 2
Kontron’s COMe-cSE6 incorporates the AMD G-Series processor in a compact footprint with a Type 6 pin-out. COMe-cSE6 is optimized for performance-intensive systems with limited power consumption.

Type 6 builds in future design options, as the pins previously assigned to the IDE interface in Type 2 are now reserved for future technologies still in development. Such possible future technologies could be the implementation of SuperSpeed USB, with 16 free pins offering sufficient lines to implement four of the eight USB 2.0 ports as USB 3.0 ports instead. Type 6 also offers configurable Digital Display Interfaces (DDI) SDVO, DisplayPort and HDMI/DVI along with 23 PCI Express Gen 2 lanes. Designers have more to work with than in Type 2,  including greater native display options and higher serial bandwidth.

Medical systems illustrate the potential of improved graphics performance. Systems enabled with more powerful graphics display and processing features allow medical professionals to simultaneously access multiple displays of patient information. For example, a technician could be charting current health information or accessing records via one display, while viewing the patient’s current health status such as blood pressure or respiration on a second display. Such a system eliminates the need for a costly workstation and still provides all the interactive, real-time data access required for proper treatment protocols. Perhaps most importantly, the addition of native support for all the newest display interfaces simplifies carrier board designs, reducing time-to-market and total cost of ownership for graphics-intensive applications. The extensive PCIe support in Type 6 underscores the overall trend of moving away from legacy parallel interfaces towards pure serial embedded system designs for higher bandwidth and reduced latency.

Type 10 evolved from Type 1, and is different from all the other COM Express pin-outs in its use of a single connector. Where options like Type 6 use both of the COM Express standard’s two 220-pin connectors, Type 10 relies on just one – making it ideal for smaller, portable applications.  The COM Express mini is designed to deliver power-saving x86 performance on a footprint that is the size of a credit card – a mere 55 x 84 mm.

Type 10 addresses the requirements of more compact processors, but there are distinct differences when migrating from Type 1 even though both pin-out types are compatible. In pin-out Type 1, SATA ports 2 and 3 are assigned pins in rows A and B, but these are no longer reserved in pin-out Type 10. The pins could still be used as SATA ports, but are now reserved for other purposes such as USB 3.0. When migrating to Type 10, it is recommended not to wire SATA 2 and 3 over the module connector so the modules remain compatible, and they are ready for USB 3.0 at the same time.

Serial ports are now supported with Rev 2.0 Type 10. Formerly used for VCC 12V, manufacturers such as Kontron ensure compatibility with existing carrier boards by integrating a protective circuit on the module. This way existing carrier board layouts do not have to be completely modified and can easily and cost-efficiently use these new capabilities.

Another difference is that Type 10 uses the second LVDS channel, TV out and VGA to support the SDVO port (or alternatively DisplayPort or HDMI/DVI) via DDI. Type 10 ultra-compact modules provide native support for both the latest display interfaces and dual independent displays because of LVDS channel support. Both Type 10 and Type 6 now also support SDIO, multiplexed on the existing GPIO signals. Required for many legacy systems, the flexibility of the PICMG standard is illustrated with the option of two 3.3 V TTL serial ports that have been added.  These ports can be used for RS232, RS485, the CAN bus, or other two-wire interfaces.

Evaluating the Smallest Options (Mini, SMARC and Qseven)

New and innovative applications, especially in the mobile and handheld markets, are driving change in the COM platform. Customers are looking for handheld HMIs and rugged portable mobile devices – potentially requiring access to new interfaces in a smaller, flatter form factor suited to tablet devices. Smart Mobility ARChitecture (SMARC) has entered the playing field as an alternative to the COM Express mini, suited for these types of applications. SMARC has several new interfaces such as MIPI CSI and other camera interfaces, serial peripheral interface (SPI), bus and I2S, which are not currently supported by COM Express. SMARC also adds value in its ability to connect. Using new interfaces, devices can more readily connect GSM or other wireless LAN protocols with CPU performance. SMARC was initiated by the Standardization Group for Embedded Technologies (SGET) two years ago; the standard is gaining high visibility based on its ability to use either ARM processors or low power x86 processors, as well as its support of connected devices required in the IoT arena.

Prior to SMARC, COM Express mini was the only feasible platform option for the smallest, most portable devices. Today designers have a choice, largely driven by where they are in the design cycle. If a design is in its earliest states and the carrier board is in development, SMARC could provide an attractive platform option for a connected, embedded application. If the design already has a carrier board developed and a COM Express COM deployed, upgrading performance to the COM Express mini is the logical design approach. It should be noted that SMARC is also considered a successor for the Qseven COM standard. They are similar in size and power dissipation, however SMARC offers more pins in its MXM3 edge connector in contrast to Qseven’s MXM2 edge connector (Figure 3).

Figure 3
The Kontron SMARC-sXQU is designed for applications in which lower energy consumption and smaller product dimensions take precedence over higher performance. It is equipped with Intel Quark X1000 series processors, as well as up to 1 GB DDR3 RAM, with the option of ECC.

The Future of COMs

COM Express manufacturers are committed to keeping customers up to date with the latest chipset technologies, for example ongoing advancements from Intel and AMD. It is important that each COM Express offers new features and functionality based on the types of applications that are being developed. Yet new generations of the Atom chipset as well as future Core platforms offer new serial interfaces such as camera or SPI, which are not defined on either Type 6 or Type 10 COM Express. New pin-outs are likely to unfold in the near term; COM Express will most likely continue to innovate in order to continue its stronghold and maintain a leading design position as applications and devices get smaller and become more tablet-oriented.

That innovation could come in the form of adding greater software standardization to the specification. The API that already exists in each COM Express type may be extended with improved functionality and standardized software support, allowing developers more capability on the hardware side of the design.  With an improved middleware interface, developers would have a simpler path to implement their GUIs or fine-tune performance to application-specific requirements. For example, Kontron’s Embedded API (KEAPI) adds a software library that enables programmers to easily create applications for monitoring and control of hardware resources. Improving API functionality would lead to greater innovation overall, for example using middleware to more easily port applications such as IoT or sensor data monitoring.

The core values of COMs are well-supported in the COM Express standard – enabling flexible, scalable, long-life solutions that get to market quickly. And with continued innovation, COM Express has an important role to play in the small footprint designs that are driving connected embedded applications worldwide. SMARC options and expectations for continued evolution of COM Express pin-out types are keeping sophisticated, small form factor design poised to make a real difference. As key markets evolve with greater focus on IoT, environments such as connected health and industrial automation can only benefit from platforms that are both proven and improving.

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