ARM-Based Modules

SMARC Specification Delivers Standardized Module Building Blocks for Ultra-Low-Power Mobile Connected Applications

A new COM-like modular specification offers a path to increasing designs of low-power and mobile systems primarily oriented around the ARM architecture.


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The requirements of today’s new range of smart connected tablet and mobile tool applications go beyond technology and power specifications to also include rugged extended lifecycle product support. These smaller portable systems challenge embedded designers with space constraints and fully sealed fanless enclosures that must operate reliably over extended periods. Designers of ultra-low-power systems have found that existing standards and higher power consumption processor architectures were not an ideal fit for these types of applications. Therefore, they have been searching for focused standards and solutions that are specifically designed to support the unique combination of computing performance, small space, power and interface requirements.

The ARM processor architecture fulfills these application demands with processors that are small in size and height, do not require a chipset, and offer long product life up to 15 years. In addition, ARM offers simplified passive cooling and thermal management to ensure higher system reliability that also provides an optimized platform for higher density systems. What has been needed is a strong ecosystem of ARM-based hardware and software suppliers that can streamline the development of ARM and SoC subsystems in low profile designs.

Answering the call for more focused subsystem resources, a new vendor-independent standards organization has been formed. The goal of the new Standardization Group for Embedded Technologies (SGET) is to help speed development of standardized hardware and software solutions for embedded computing. The first SGET working group created under SGET has ratified a versatile, small and ultra-low-power Computer-on-Module standard that it has named SMARC for “Smart Mobility ARChitecture.” Kontron played a leading role in the development of the specification, which had the working title ULP-COM. The SMARC specification brings standardized ARM/SoC-based miniature format building blocks as a welcome solution to fill a very significant gap in the embedded market.

Key SMARC Features

The SMARC specification is characterized by its extremely flat form factor dimensions that are as low profile as 1.5 mm from the top of the carrier board to the bottom of the module. It features an optimized pin-out for SoC processors that uses a 314-pin connector with a height of just 4.3 millimeters (the MXM 3.0) that is pitched at a 0.5 mm right angle. This robust, vibration-resistant connection method was defined to specifically meet smaller mobile/portable system design needs for very low-profile, high-performance, rugged and cost-effective modules. Matching various space-constrained needs, SMARC defines two module sizes: 82 mm x 50 mm and 82 mm x 80 mm. And solving the portable systems power limitations, the SMARC module power envelope is typically under 6W during active operation to deliver fanless and passive cooling.

SGET initially defined the SMARC module standard for ARM SoCs as this processor architecture has become popular, and thus familiar, for tablet computer and smartphone designs. The specification, however, is designed to be flexible enough to accommodate alternative low-power tablet-oriented x86 or RISC processors and SoCs and CPUs, such as tablet-oriented x86 devices, and other RISC CPUs may be used as well.

To maintain low costs, low power and small physical size, the SMARC specification integrates the core CPU and support circuits, including DRAM, boot flash, power sequencing, CPU power supplies, Gigabit Ethernet and a single channel LVDS display transmitter together on the module. SMARC modules are designed to be used with application-specific carrier boards that implement other features such as audio CODECs, touch controllers and wireless devices. The advantage of a modular approach is that it delivers flexible building blocks that provide OEMs with scalable technology and upgradeability that results in faster time-to-market while still maintaining low costs, low power and small physical size (Figure 1).

Figure 1
Designed to help ultra-low power SFF system OEMs drive down the cost of development, the Kontron SMARC-sAT3874 features an extremely low 3W TDP (Thermal Design Power) and extended operating temperature range of -40°C to +85°C making this SMARC module ideal for space-constrained, fanless and harsh environment applications. The Kontron SMARC-sAT3874 offers a cost-effective and highly scalable COMs building block that can be used by a broad range of SFF systems.

How SMARC Differs from COM Express

Prior to the SGET SMARC specification, previously defined computer module specifications were primarily based on x86 technology and its associated chipsets. Standards defined for x86 were developed mostly with PC designs in mind that required support for chipset-compatible interfaces. A prime example is the COM Express standard, which is optimized for PC-based applications and hugely successful. The COM Express feature aligns very well to PC chipsets and offers broad support for USB, multiple PCI Express (PCIe) lanes, PCI Express Graphics, the LPC bus and the PCI bus. Additionally, based on PC power requirements, the COM Express definition offers power pins supporting more than 100W.

On the other hand, SMARC targets lower power, smaller form factor systems. The SMARC pin-out is optimized for the features common to ARM CPUs that may not be required for PCs. These features include parallel LCD display interfaces, serial and parallel camera configurations, multiple I2C, I2S and serial port options, and USB operation/support signals.

COM Express and SMARC modules do share some features in common including a limited number of PCIe, SATA and USB ports. However, how these features are combined is different due to the specialized features of interest that need to be utilized on a SMARC module.

ARM-Based Interface Support

Giving designers a standardized feature set specifically matched to ARM I/Os, the SMARC specification supports cost-effective Parallel TFT display bus and MIPI display interfaces.  SMARC modules also offer additional display interface support with full featured implementation of HDMI ports, 24-bit parallel RGB LCD data and control signals, single channel LVDS LCD 18/24-bit, and panel support signals (I2C, Power Enables, PWM). Dual channel LVDS support is a needed feature to drive high-resolution panels, and SMARC accommodates a second LVDS channel to be implemented on the carrier board. Embedded DisplayPort is planned for future designs.

An industry first for module standardization, SMARC offers camera interfaces with consumer camera and phone memory cards supported by multiple Serial Peripheral Interface (SPI) links and SDIO (Secure Digital I/O) interfaces. SMARC also supports general purpose I/O with 12 GPIO signals, CAN error signaling, HD audio reset and PWM/Tachometer capabilities. Because real-time Ethernet and Fieldbus implementations typically use a number of LEDs to indicate the system status, the SMARC specification selects four GPIOs to support this LED functionality (Figure 2)

Figure 2
The SGET SMARC standard offers new interface support particularly suitable for ARM architecture-based platforms dedicated camera interfaces and video display LVDS outputs.

Resources to Streamline Development

An important aspect of SoC-based hardware is that it requires a different design approach to address a distinctive I/O mix. Beside the flexibility and scalability a module approach provides, designing with high-end ARM processors brings an element of complexity and design risks. That is because next-generation ARM processors integrate high-speed memory and I/O buses, which need complex routing. More and more customers are now looking for development and validation resources to mitigate design challenges and allow them to just focus on their dedicated application I/O development. Opting for a module design approach delivers cost benefits especially for higher volume applications compared to a dedicated SBC design.

For a supplier to be a valuable partner in helping OEMs wade through ARM-based embedded design complexities, they need to have proven capabilities in leveraging existing standards and the ability to simplify hardware integration by offering standardized building blocks that enable leaner development schedules.

SMARC modules offer building blocks in the development of ultra-low-power applications. Design resources in the form of a complete SoC solution are available that include the carrier board, firmware and drivers, and operating system. Offering multiple layers that make up a complete ARM solution provides time-to-market development benefits and added value for OEMs

SMARC evaluation carrier boards eliminate some design complexities to allow application developers to get up and running quickly on the SMARC modular platform. Evaluation carrier boards let OEMs install the SMARC module best suited to their application needs, includes support for a broad range of interface options, and offers dual power options for mobile and stationary applications (Figure 3).

Figure 3
Kontron’s new ready-to-use SMARC Starterkit includes all the cables and necessary components, including a display and power supply. The SMARC Starterkit can be delivered with the pre-installed SMARC module of choice, operating system, a Board Support Package and cooling solution, which allows developers to immediately evaluate their application.

There is also a new SGET Design Guide for SMARC, which further helps to facilitate SMARC carrier designs, thus accelerating their time-to-market and helping OEMs achieve an advantage in the competitive mobile application market. The Design Guide provides routing guidelines, reference schematics and useful development recommendations for SMARC carrier design, enabling OEMs to save significant time generating their own carrier board.

There are many factors to consider when deciding on a Computer-on-Module/baseboard approach versus a full custom SBC design. This crucial decision depends upon many factors including an organization’s business model and customer requirements.

SMARC: A Specification for the Future

With scalable SMARC module building blocks, designers now have a standardized solution to help them achieve their performance/power ratio requirements. And, performance in SMARC modules is forecasted to further increase with future technical progress. This also translates into a more cost-effective design approach that permits portable and fully enclosed systems to have a competitive price. Additionally, the lower power consumption from ARM-based solutions supports simplified cooling methods that significantly contribute to lower costs from a less-complicated mechanical design that results in decreased assembly requirements and higher reliability because of a fanless design. While these requirements may previously have had solutions, it would have required additional design compromises, time and resources.

SMARC modules promise standard solutions for a diverse range of applications—from industrial automation to graphics and image-centric devices that must operate at extremely low energy consumption and withstand severe environmental conditions. Other harsh condition small form factor systems can also benefit from SMARC feature advantages such as applications in the military, digital signage and medical markets. In addition, the SMARC specification offers support for Linux, Windows Embedded CE, VxWorks and a variety of real-time operating systems, so embedded OEMs are able to leverage a growing and strong ecosystem of development partners.

There continues to be increased embedded system OEM market acceptance and favorable customer reviews of the connector definition, which encourages more Computer-on-Module suppliers to support this new standard, resulting in a comprehensive ecosystem for ultra-flat ARM/SoC-based Computer-on-Modules in miniature format. The specification is available free of charge on the SGET website.



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