A fresh start for mobile applications with Qseven

Computer modules (COMs) have been an established technology for the development of systems and devices for more than 10 years. They shorten development time and costs while providing flexibility and scalability. Developers can focus on their core competencies and buy the required processor technology in the appropriate format. However, early standards such as ETX and XTX are no longer up to date, as chip technology has changed since the introduction of these standards. Even the COM Express standard - still the first choice for power-hungry, x86-based systems - calls for technical compromises due to its long history. For instance, the standard allows for a maximum power consumption of 140W, while current processors use less than 5W.

In general the market trend is towards smaller and more mobile applications with low power consumption. Industrial systems are implementing up-to-date graphical user interfaces, thereby moving closer and closer to the smartphone and tablet worlds that we are familiar with from the consumer sector. Against this backdrop, Qseven was introduced in 2009 as a new and open standard that despite competition from increasingly small COM Express form factors in the x86 world, is now well established. Designed from the outset as a multi-platform standard, Qseven only required minimal extensions to officially release the standard for the ARM platform with revision 1:20 in the summer of 2010. This evolved Qseven into the only established market standard to support both ARM and x86 processors.

The name of the standard is derived from the module size which measures 7cm by 7cm. This footprint enables the development of a high-performance, very power-efficient platform providing an extensive choice of interfaces in a compact size to allow integration in handheld devices. What makes Qseven especially attractive is its modern concept, which provides a clean slate without legacy issues; the connector concept, which has been adapted to the special requirements of compact and ultra-compact applications; and fanless cooling.

Unlike most previous module standards, Qseven does not use an expensive board-to-board connector, but a less expensive MXM connector with 230 pins, 0.5mm pitch and standardised, vendor-neutral PIN assignments. This connector type is already being used for fast notebook graphics cards and is therefore specified for the high data rates of PCI Express Graphics. The connector is very robust despite its small size. It is available in four different heights and even in a rotated version. The connector is only required on the carrier board; the connection on the CPU module are gold fingers found directly on the board so that no additional costs are incurred.

Less power-hungry

The power consumption of Qseven modules has been set at a maximum of 12W to suit modern mobile technologies. However, at 5W many current modules remain well below the maximum specification. Qseven defines a power supply of 5V; this is easy to use and, as a rule, already provided on the carrier board. To allow developers to take advantage of the advanced power saving options, a 5V standby voltage is required. All signals for easy implementation of battery-powered devices are defined in the standard.

Even at 5W heat is created and must be dissipated. Therefore, the Qseven modules have a 5mm-deep layer at the top for heat dissipation. All internal and external layers of the board are made of solid copper and thermally connected with numerous vias. The internal layers are widely connected to the heat-generating components such as CPU, chipset and memory.

Since soldered components are used, the heat generated is transferred in part to the circuit board and from there transported via the copper layer to the heat dissipating layer. The last stage is the heat spreader, an aluminium or copper plate with a thickness of approximately 3mm. From the heat spreader onwards, standard concepts are used to cool the overall system.

Standard without legacy limitations

Qseven defines only the latest interfaces to support the features of current and future chipset/CPU combinations. The following interfaces are defined in the Qseven specification: 4× PCI Express ×1 lanes, 2× SATA, 6× USB 2.0, USB 3.0, 2× SDIO, I2C bus, high definition audio and 1× Gigabit Ethernet. The available graphics interfaces include LVDS 2×24 bit, SDVO, DisplayPort and HDMI.

Qseven COMs come equipped with additional functions for industrial applications. Examples include watchdog timers, LDC brightness control, BIOS user storage and system temperature outputs. To ensure a consistent software interface for these functions, the Embedded Application Programming Interface (EAPI) from PICMG was implemented in the Qseven specification. The EAPI is a cross-platform middleware that simplifies the access and control of hardware resources in embedded applications. This makes it possible to swap Qseven modules from different manufacturers without any changes to the hardware or software.

Future development is sure to bring even more power-efficient X86 and ARM processor platforms to the marketplace. Unlike previous module standards, Qseven is clearly designed for mobile and battery-powered applications with interface options that have been future-proofed to suit the most advanced mobile chipsets.

More information about Qseven is available on the website at www.congatec.com.