Future Electronics – Systems-on-Module: Suitable for First Time Embedded Computing Designs?

By: Patrice Brossard, Technical Solutions Manager, Future Electronics

As consumers, we have become accustomed to the permanent availability of internet access on touchscreen devices we can easily carry in a pocket or a bag. This is leading to dramatic changes in users’ expectations of many kinds of previously standalone and single-function products.

These new expectations are not only having an impact on personal consumer devices. Intel, for instance, has demonstrated a concept for an in-store advertising panel; its futuristic design is a huge 2 x 1m touchscreen with a camera that can ‘recognize’ shoppers and serve up appropriate advertising messages. The touchscreen lets the shopper click on items of interest, go online to find out more information or reserve the item for collection at a checkout desk.

This is a challenge for the panel’s manufacturer; conventional advertising panels are, in essence, no more than a light box or a large display screen. But the trend is for this kind of ‘dumb’ product to become an application-specific computer; this massively increases the complexity of the design.

So what is the best way to streamline the architecture and avoid the difficulties of introducing a complex processor into a previously simple end product design?

Flexible Off-the-Shelf Options
Perhaps the most obvious choice is to use one of the hundreds of embedded or industrial computers offered by manufacturers such as Advantech or Technexion. This provides a complete hardware platform including not only the processor and main memory, but also storage, board-to-board interfaces, networking capability, supervisory functions and an AC/DC power supply.

Although there is a very wide choice of these off-the-shelf products, the problem with them is precisely that they provide a complete platform with a huge range of built-in functions; this means that they are relatively expensive, and also inflexible. In an embedded computer, the specification of everything, down to the peripherals and interfaces, is chosen by the computer manufacturer, not by the customer.

For some users, then, a System-on-Module (SoM) might be a better choice. An SoM is an electronic module that provides the basic components of an embedded computer. And it is popular because it gives the user an easy way to support advanced applications and connectivity without needing knowledge of the way to design a processor board.

In Other Words, the Design Team Benefits from:

  • A shorter development time
  • The flexibility to choose exactly the peripherals, storage and interfaces required for the application

At the same time, a module is cheaper than a complete embedded computer, and the designer avoids paying for features or peripherals that the end product does not need.

SoM Choices
An SoM incorporates the circuitry essential to all embedded applications. It provides a microprocessor that interfaces with RAM and flash memory, a power-management system, and Ethernet, USB and other interfaces. The module manufacturer handles all the difficulties of processor implementation: board layout for a fine-pitch BGA device, high speed routing, design verification, EMC conformance, and the significant effort involved in board bring-up and Board Support Package (BSP) development.

Today the Market Offers Two Main Types of SoM:

  • Fully modular solutions are designed to sit on a carrier card. Standard carrier cards are available from SoM manufacturers. In some circumstances, the carrier card may be customized, and this gives the designer complete flexibility to design a board with the exact mix of storage, peripherals, interfaces and connectors required, and allows for the use of a general-purpose SoM.
  • Integrated solutions do not require a carrier board and provide a fixed set of connections and interfaces, of which the most commonly found are SPI, I2C, UART, CAN, PCI, PCIe, SATA, and MMC/SD/SDIO. This type of system is better described as a single-board computer (SBC) or Computer-on-Module (CoM). Many CoMs also provide on-board audio functions, display controllers and camera interfaces.

It follows that a true SoM on a custom carrier board can be sized to fit the application’s mounting requirements precisely. The CoM market, by contrast, is highly standardized, and CoM boards’ form factors are defined by standards bodies (see Figure 1).

Figure 1: form factors of the most common embedded CoM and SBC standards

Figure 1: form factors of the most common embedded CoM and SBC standards

Of the standards shown in Figure 1, the most commonly used in embedded designs are the following:

  • Q7
  • COM Express (also known as ETX Express)
  • PC/104 (ISA)
  • PC/104+ (PCI)
  • PC/104e (PCIe)
  • ITX (Pico-ITX)

The standard specification generally defines not only the size of the board, but also the connector types used. The location of the connectors might also be specified, or decided by the board manufacturer.

The issue for the embedded system designer is to choose the level of integration that best fits the application. As ever in electronics, the trend is towards more and more integration; some of the most innovative designs are appearing in boards that have a very small form factor.

Advantech, for example, offers PC/104 (96 x 90mm) computer modules. In any two applications, the module could offer two widely differing ranges of functions in exactly the same form factor. Several modules for embedded computing designs are based on the x86 architecture, with up to 1GB of DDR3 memory, dual 10/100/1000 Ethernet interfaces, an audio codec, a mini-PCIe expansion slot, and SATA and dual-display capability.

Figure 2: the latest Advantech PC/104 board. This standard form factor is still very popular

Figure 2: the latest Advantech PC/104 board. This standard form factor is still very popular

Another popular form factor is the COM Express® (or ETXexpress) format. One of the latest modules available from Advantech is shown in Figure 2. COM Express is the first independent module standard to support very high-speed interface technologies such as USB 3.0. Embedded applications, however, normally favor the use of more mature interfaces such as PCIe and SATA.

Figure 3: high-end COM Express module from Advantech

Figure 3: high-end COM Express module from Advantech

Another proven SoM supplier, Technexion, offers the designer a choice between ARM-based and x86-based modules. Usefully, the two families of boards are pin-compatible with each other.

They are produced in the new ‘EDM Compact’ form factor. The aim of the developers of this new open standard is to provide reliable and interoperable hardware, so that users can simply swap modules in and out of a design – a ‘modular computing’ approach.

EDM Compact is very similar to the Q7 standard, making use of a common connector which carries all signals (such as Gigabit Ethernet, SPI and HDMI). This board, shown in Figure 3 offers up to 2GB of main memory, a 10/100/1000 Ethernet interface, USB 2.0, CAN, PCIe, SATA, an audio codec and strong video capabilities. All of this is available in a module qualified for industrial use, and in a smaller outline (60 x 82mm) than the PC/104 form factor.

Application Development Resources
One of the biggest advantages to system developers using an SoM is the speed with which they can progress to application development. Most SoMs incorporate a BSP based on Workbench. Workbench, an integrated development environment, provides a graphical and highly automated environment that makes it easy even for inexperienced developers to create applications on a choice of operating systems, including VxWorks, Linux, Android, Windows Embedded and Integrity (from Green Hills Software).

Users should also expect the SoM manufacturer to provide a complete set of drivers for devices on the board. Device driver development requires a high level of expertise, and would distract attention and resources from application development if the SoM user attempted to undertake it. The SoM supplier should take care of drivers in the following categories:

  • Protocols and communication (such as TCP/IP, 10/100/1000 Ethernet, Profibus, PCI, PCIe, PCMCIA)
  • Wireless (Wi-Fi, SDIO, Bluetooth, ZigBee, GPS, RFID, IrDA, Wireless USB, GSM/GPRS)
  • Peripherals (LCD, touch sensing, SPI, I2C, real-time clock, DMA)
  • Storage (SATA/PATA, non-volatile memory, SD/MMC/Compact Flash, smart card)
  • Multimedia (MP4/H264 codec, camera, audio)

SoMs in Use
Thanks to the use of a SoM, Intel’s vision of smart display panels has already been realized in part. Future Electronics recently supported a European manufacturer of LED public information panels (for use for instance in airports and train and bus stations) which has added connectivity and user-interface functions to a previously simple panel design.

This manufacturer found that an architecture based on the use of an industrial PC was expensive and incompatible with the environmental constraints of the application.

Its successful design used an SoM carrying an ARM based processor. The module was connected to the internet via a GSM mobile phone network; wireless connectivity was implemented with a Sierra Wireless module mounted alongside the SoM.

Since the BSP and device drivers were provided by the SoM manufacturer, the designers were able to start developing their application early in the project. And by using an SoM, they were able to introduce a completely new hardware architecture based on an embedded computer, without having to handle the power, thermal, board-layout and compliance issues involved in implementing a complex processor design.

Other Telling Examples in Which an SoM Has Been Used Successfully Include:

  • Adding a sophisticated human-machine interface to a vending machine – this calls for a computer module which is easy to use, and offers high computing performance and high reliability.
  • Public information panels containing a full-HD LCD screen. This application requires video capability with an HDMI interface.

Enhancing Value of End Product
The examples above show, there is an opportunity for manufacturers of standalone products to create a new, premium product without a total reconfiguration of the design operation. Modern processors are enormously capable devices, but the use of an SoM insulates design teams from the difficulties involved in realizing a processor design.

The latest SoMs from suppliers such as Technexion, Advantech and iWave provide a way to radically rethink end product designs, without a huge investment in new design staff or new expertise.