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SODIMM-sized CPU module runs Linux

Sep 19, 2008 — by LinuxDevices Staff — from the LinuxDevices Archive — 22 views

Emac has introduced an SO-DIMM-sized processor module built around an ARM9-based Cirrus EP9302 SoC (system-on-chip). The SoM-9307M targets development of customized products and applications, and runs Linux, Windows CE 6.0, or the .NET Micro Framework.

(Click here for a larger view of Emac's SoM-9307M)

The Cirrus EP9302, which forms the core of the module, is a highly integrated SoC that includes an ARM920T processor core, a “MaverickCrunch” engine, and numerous peripheral interfaces. Cirrus describes MaverickCrunch as “an advanced, mixed-mode math coprocessor that greatly accelerates the single- and double-precision integer and floating-point processing capabilities of the ARM920T processor core.”

EP9302 SoC block diagram
(Click to enlarge)

Key specifications of the SoM-9307M, as listed by Emac, include:

  • Processor — Cirrus Logic EP9302 ARM920T SoC clocked at 200 MHz; includes MaverickCrunch floating point math engine
  • Memory:

    • “Up to 128MB” of SDRAM; 32MB standard
    • 128KB of programmable serial flash

    • “Up to” 64MB of flash storage; 32MB standard
  • Networking — 10/100 Ethernet
  • Other I/O ports:
    • LCD interface with 2D acceleration up to 1024 x 768 pixels
    • Touchscreen interface
    • 12-bit 4, 5, 7 or 8 wire analog resistive touchscreen interface
    • 64-key (8×8) keypad interface, with auto debounce, scanning, and decoding
    • 3 x serial ports
    • 2 USB 2.0 ports
    • 2 x SPI ports
    • SD/MMC interface
    • 1 I2S audio port
    • Timer/counter and PWM (pulse width modulation) ports
    • Digital I/O: 32 general purpose I/Os
    • Analog I/O: 8-channel 12-bit analog-to-digital converter

  • Power supply — 3.3VDC, with 300mA typically required
  • Operating temperature — 0 to 70 deg. C
  • Dimensions — 2.66 x 2.375 inches (67.6 x 60.32mm)
As Emac notes, the SoM-907M has the same dimensions as a SODIMM memory module, but with its height increased. The SODIMM connector is capable of passing all the board's signals through to a custom carrier board, including the 22 address lines, 16 data bus lines, and control lines that are part of the EP9307 system bus.

Like other products of its type, the SoM-907M is intended for ultimate installation on a custom carrier board. Emac says it can assist with board development, and a “semi-custom hardware platform can be developed in as little as a month.”

Emac's SoM-150ES carrier board, with SODIMM-based CPU module in place

To complement this, the company offers an off-the-shelf carrier board, the SoM-150ES (pictured above with one of the company's other SoMs in place). The SoM-150ES uses a “half-EBX” form factor measuring 6 x 4.37 inches (152 x 111mm), and offers features and “real-world” connectors that include the following:
  • 1 x 10/100 Ethernet port with RJ45 jack
  • Battery for nonvolatile RAM and real time clock
  • 2 x USB host ports
  • 1 x USB device port
  • MMC/SD Flash Card Socket
  • 2 x RS232 ports
  • System reset button


The resident serial flash memory on the SoM-907M can be programmed using a serial bootloader, via either the unit's RS-232 port or its JTAG port. Emac notes that software for the board can be based on Linux, Windows CE 6.0, or the .NET Micro Framework, a Microsoft toolkit and runtime aimed at deeply embedded applications.

Emac maintains a Linux build system for the SOM-9307, using the popular OpenEmbedded framework. Currently, a 2.6.20 kernel is used, along with patches to support the SOM-9307, the vendor says. Components of the RFS (root filesystem) include:

  • Busybox 1.7.2 or higher
  • Hotplugging support
  • APM utilities for power management
  • Dropbear SSH server
  • Telnet/FTP support running under inetd
  • Busybox-httpd HTTP server
  • JFFS2 filesystem with utilities
  • “Many” other utilities
  • Optional Minimo (Mozilla/Firefox based) brower (requires 64MB version)

Additionally, Emac can supply custom Linux builds on request, it says.

Emac also offers a iPac-9302 PC/104 board based on the Cirrus EP9302 SoC.

Further information

Available now, the SoM-9307M costs $170 with 32MB of flash and 32MB of RAM, or $190 with 64MB of flash and 64MB of RAM. A standard ARM build of Windows CE 6.0, with license, adds another $25. The SoM-150ES carrier board ranges from $190 to $190, depending on included features, Emac adds.

Further details of the SoM-9307M are available from the Emac website, here.

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