The Standardization Group for Embedded Technologies (SGET) recently ratified a standard for highly compact ARM-based computer-on-modules (COMs). Formerly known as ULP-COM, the “SMARC” specification defines 82×50 and 82×80 mm formats using 314-pin MXM3 connectors, and is designed for low-power mobile and embedded device applications.
SMARC (Smart Mobility ARChitecture) originated from the ULP-COM format proposed by Kontron last Fall. Considering the standard has been endorsed by 34 SGET members, including top embedded competitors like Adlink, Advantech, and MSC, SMARC represents a turning point for ARM in the embedded boards market.
SMARC’s two format options
ARM modules and single-board computers (SBCs) have been around for years, but have grown much more common in the last year or two as ARM has spread further into the general embedded market, following the lead of commercial smartphones and tablets. While previous ARM modules have typically been custom designs, they are increasingly being adapted to other module form-factors, including the popular QSeven format, which is now being maintained by SGET along with SMARC.
SMARC is the first COM standard to be built specifically for modern ARM-Cortex system on chips (SoCs), aiming to efficiently pass along ARM benefits such as low power consumption to COTS designs. Despite this focus, the standard also supports the use of low-power x86 and other RISC processors.
The SMARC standard defines two profiles: 82x 50mm (3.2x 2.0 in.) and 82x 80mm (3.2 x 3.1 in.). Module profiles can be as large as 2.5mm, which accounts for 1.2mm board thickness, 1.3mm bottom-side component thickness, and 3.0mm topside components. The modules use 314 edge fingers combined with a 0.5mm-pitch right angle connector. This 314-pin design is based on, but not compatible with, the connectors used by MXM3 graphics cards. To accommodate a range of baseboard component heights below the SMARC module, MXM3 connectors are available with several alternate slot elevation options, ranging from 1.5 to 5 mm or more.
SMARC footprint and height dimensions
(click images to enlarge)
The SMARC input voltage requirement is 3.0 to 5.25 Volts, allowing operation from 3.6V Li-Ion batteries, and fixed 3.3V or 5.0V DC supplies. According to SGET, the typical power range is 2 to 6 Watts, enabling fanless and passively cooled designs as well as mobile devices.
While SMARC lacks support for features typical of x86-oriented COM Express modules, such as support for massive arrays of USB ports, LPC buses, PCI ports, and PCI Express (PCIe) lanes, it does support limited numbers of PCIe, USB client/host (OTG), and SATA ports. The main focus is on features typically found in today’s ARM Cortex-A9 devices, including LCD display interfaces, camera input, SD/eMMC cards, and I2C, I2S, and serial-port options.
SMARC module interfaces include:
- Display — 24-bit parallel RGB LCD; LVDS LCD (18- or 24-bit); HDMI
- Camera — serial and parallel
- SDIO — 4-bit SDIO; 8-bit eMMC with optional boot
- SPI — 2x with optional boot
- I2S — 3x for audio codecs, baseband modems, touch controllers
- I2C– 4x I2C (power management, general, camera, LCD display ID); HDMI
- Serial — 4x asynch serial (2x 2-wire, 2x data-only)
- CAN bus — 2x channels
- USB — 3x USB 2.0 (1x OTG, 2x host)
- PCI Express — 3x PCIe x1 lanes
- SATA — 1x (Gen 1, 2, or 3)
- Gigabit Ethernet — 1x analog MDI interface
- SPDIF — In and Out for audio
- Watchdog — 1x timer
- GPIO — 12 lines
- System/power — resets, power/system management, battery, etc.
- Boot source — 3x pins with 4x module- and 4x carrier-boot options
- Alternate Function Block — 20x AFB pins
- JTAG — available on “separate small form-factor connectors”
SGET rightfully trumpets the quick adoption of the SMARC standard. Already SMARC modules are being developed by Kontron, Fortec AG, Adlink, and others. It’s unclear whether SMARC will match the popularity of SGET’s Qseven standard, which is now used in dozens of primarily x86-based COMs, but it appears to be well on its way.