April 2015 PC/104 Embedded SFF - Right Sizing Your Embedded Application with the OneBank Spec.

Right Sizing Your Embedded Application with the OneBank Specification

April 6th, 2015 By Matthew Henry, ADL Embedded Solutions

An evolution that’s in step with the ascent of speedier and more sophisticated bus architectures is one reason PC/104 effectively serves embedded applications across a wide range—encompassing machine vision, security, high-speed data collection, and more.

Most embedded products will provide adequate processing power when appropriately sized for the job at hand. It is I/O bandwidth and product expandability that become critical data points when defining your platform and application. Data storage I/O can bottleneck your system and keep it from performing at an optimal level. Is it very hot or cold in your area of operation? Is your application mobile or do you have limited power available? It is these factors that help differentiate one form factor from another.

Intel ® Architecture Raises the Bar

Perhaps you need a lot of horsepower for data processing, or you need a Windows-based platform. The PC/104 footprint allows enough PCB for the implementation of some of the highest performers available from the Intel® Core™ processor product lines. Currently, PCIe/104 is able to support the Intel 4th Generation Intel® QM87 chipset with the Intel® Core™ i7-4700EQ processor, giving it a robust set of features with near-server class performance employing six SATA /mSATA ports up to SATA 6 Gbs, USB 3.0 and advanced video like DisplayPort 1.2, HDMI 1.4 and eDP.

Common legacy interfaces are still included for those looking to retrofit an existing platform, like VGA video, RS-232 COM ports, dual Gigabit Ethernet and the ability to connect to a host of peripheral I/O boards to get to the interface needed via the PCIe/104 bus. 3rd and 4th generation Intel Core architecture raises the level of performance in the PC/104 market space. This architecture has opened the door to emerging markets including machine vision, high-speed data collection, security/surveillance and mil-aero, to name a few.

The PC/104 Embedded Consortium has released the OneBank™ specification, opening another door for peripheral designers. General consensus for peripheral designers has been that the x16 lane of the PCIe/104 connector is mostly wasted real estate, since most peripherals typically require a x1 PCIe lane only. The four x1 lanes in the PCIe/104 connector are carried in the first of three banks. The other two banks can vary, depending on whether you have a Type 1 or Type 2 PCIe/104 implementation, with the first bank remaining constant for both PCIe bus implementation types. The OneBank connector contains four x1 lanes or can be utilized as a single x4 lane. Care has been taken to ensure that the OneBank connector is compatible with the three-bank PCIe/104 bus architecture and can be mated directly to a full-sized three-bank connector. See Figure 1.

The Greatest Threat?

Figure 1: ADLE3800PC (Type 2) with OneBank™ Intermediate Peripheral Card.

There are several environmental factors that can put your hard work into an early grave when defining an embedded computer system. The top three system killers, in no particular order, are temperature, shock and vibration, and power.

Thermal management may be the largest threat to the lifetime of an embedded design. Although your system may be operating in a benign environment, thermal pathway issues can shorten product life significantly. Thermal issues can occur in a transmissive (radiative or convective) thermal solution if the thermal interfaces are not properly aligned for optimal heat transference.

Misalignment when assembling or an extreme shock or vibration event could cause misalignment…especially if the thermal solution has not been adequately secured during system integration. Convection cooling systems are susceptible to thermal anomalies if the supplied airflow is impeded by dust buildup on fan blades, heatsinks, components and filters.

Extreme heat will not only affect the life of an embedded system, but also the performance. Most Intel architecture based embedded board designs include signaling for thermal management purposes. Onboard sensors monitor the processor die temperature as well as the board temperature at various locations and provide the necessary data for thermal management via the cooling fan (usually via BIOS and/or O/S based tool) by controlling fan rotation speed. This same technology is used to prevent an over-temperature condition within the processor by dynamically throttling back the CPU clock multiplier to try to keep it from reaching over temperature shutdown. If thermal pathway issues exist, your system could be perpetually running in a “throttled” condition, giving you less than 100 percent performance.

Headache Removal

Input power can also cause an array of unforeseen and sometimes unidentifiable problems for a system designer. While many COTS embedded products run on a single +5VDC rail, the quality of power supplied can vary greatly depending on the application. PC/104 boards are often integrated into larger assemblies such as environments where only mobile power is available. Power sources in planes, trains and automobiles vary greatly. Remote or “wearable” applications could use a renewable energy source, run on batteries, or a gas powered generator. Most ships use power from an onboard power generator to supply the onboard equipment. Most embedded boards simply do not have the necessary PCB real estate to include the power conditioning circuits that are found on desktop boards. Therefore, choosing a quality power supply with a high switching frequency can go a long way to removing embedded CPU design headaches.

Source power can pose unique problems that can shorten the life of a board. The severe power instability that can occur during a brown-out make this situation especially dangerous. This condition can send power spikes into connected equipment, often causing catastrophic component failure. Electrostatic discharge (ESD) concerns are also ever-present. ESD is always a concern when handling electronic devices, but ESD damage can also occur to a board during installation and a system where transient voltages may exist. Inadequate input filtering, hot-plugging of user interface devices, or poor grounding techniques can all lead to ESD-type system failures. Transient voltage damage can occur slowly over time, causing latent failures that are hard to identify.

Shock and vibration failures are much less subtle. Vehicles provide excellent examples of both shock and vibration. Provided that the necessary enclosure space is available, what are the chances of an ITX, mini-ITX, COM or even an Epic board surviving a vehicle crash, extreme airplane turbulence, or the concussion blast of artillery on the battlefield? One thing is for certain, PC/104 has a high rate of survivability in extreme conditions. Larger PCBs are more susceptible to flex conditions that fall outside of acceptable norms. This can result in a higher rate of failure in a high shock and vibration environment. Smaller form factors like PC/104 have a higher survivability rate. While COM is a small form factor, it employs a modular approach that adds to the risk of a shock failure because of the added connector interface. Vibration can create resonant frequencies within a PCB and can cause solder failures. Small form factor boards survive a wider range of vibration as they are less affected by lower vibration frequencies than larger form factors.

Customization

PC/104 form factor boards offer the highest level of customization of any standards-based COTS embedded form factors. There is no carrier board to design, and generally, no onboard consumer grade connectors that limit the product implementation. I/O’s can be custom cabled to meet specific needs, allowing the board to be deeply embedded within a system. The PC/104 specification has evolved with the rise of faster and more advanced bus architectures. Slower ISA and PCI use bus interfaces (PC/104 and PC/104-Plus) similar to VME style connectors, providing a deep and secure connection to added peripheral boards, and still maintains a presence in the field on platforms that have survived for decades. The current generation of PCIe/104-Express includes support for the fastest bus architectures and is well suited to support Intel technology advances for the foreseeable future. It remains the form factor of choice for rugged, extreme temperature embedded applications.