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IoT dev kit runs uClinux on a Microsemi Cortex-M3/FPGA SoC

Dec 24, 2015 — by Eric Brown 2,744 views

Arrow’s “SF2+” IoT development kit combines an Emcraft COM based on Microsemi’s Cortex-M3/FPGA “SmartFusion2” SoC with a carrier board, and runs uClinux.

The Arrow Electronics SF2+ Development Kit, which targets security camera, communications, connected home, and Internet of Things (IoT) applications, is unusual in that it pairs the stripped down uClinux and U-boot with a Microsemi SmartFusion2 (SF2) SoC. The Microsemi SoC combines an ARM Cortex-M3 microcontroller core with an FPGA, which is said to enable capabilities like image processing, I/O expansion, bridging, and security.

SF2+ Development Kit
(click image to enlarge)

The kit was announced as a collaboration between Arrow Electronics and Microsemi. However, Emcraft Systems builds the intervening SmartFusion2 computer-on-module that integrates the SoC, and also provides the kit’s uClinux and U-boot firmware. The Arrow baseboard extends the Emcraft COM with a Timberwolf audio processor, an Arduino I/O interface, an Ethernet port, and other features (see farther below).

While Linux is dominating high-end Internet of Things devices, on the low end, it has been blocked by the fact that the only Linux that runs on ARM microcontrollers is uClinux, a very barebones implementation designed for processors without MMUs. Furthermore, it only runs on a few of the higher end models with built-in memory controllers that let them use an external DRAM chip to meet uClinux’s minimum RAM requirements. The addition of a RAM chip adds to the cost, size, and power consumption of the device, say critics, who also question performance.


Emcraft Systems, however, has been a champion of uClinux on MCUs, and contends that it’s better than solutions such as ARM’s Mbed OS for higher end MCUs like ARM’s Cortex-M3 and -M4. The company has posted uClinux and U-boot ports for both of these MCU families on Github.

Other boards that run uClinux on a Cortex-M3 include the Amptek Icon SBC. The Icon is equipped with an NXP LPC1788 chip.

Microsemi SmartFusion2 SoC

Microsemi’s SmartFusion2 SoC is equipped with a 166MHz Cortex-M3 with on-chip eSRAM and nonvolatile eNVM. The MCU is linked with an onboard, flash-based FPGA fabric. The FPGA is claimed to offer “orders of magnitude lower power operation for low duty cycle applications,” compared to mainstream field programmable gate arrays. Other SmartFusion2 SoC features include a PCIe Gen2 control plane and serial communication interfaces.

SF2+ kit simplified block diagram (left) and SmartFusion2 SoC block diagram
(click images to enlarge)

The FPGA offers 4-input LUT logic elements, embedded memories, and math-blocks for DSP processing capabilities. Different SmartFusion2 models offers tradeoffs between power efficiency, down to 7mW static power during operation, and greater security on the high end up to a DPA hardened model with AES256, SHA256, random number generator, ECC, and physically unclonable function (PUF).

The SoC integrates an Intrinsic ID secure key storage technology which offers “the SoC FPGA industry’s only PUF key enrollment and regeneration capability,” says Microsemi. The SmartFusion2 is also the only SoC FPGA protected from differential power analysis (DPA) attacks, thanks to technology from Cryptography Research Incorporated (CRI), claims the company. The SoC is also said to protect against Single Event Upset (SEU) occurrences, which can cause binary bits to change state and corrupt data and cause hardware malfunction.

Emcraft SmartFusion2 module and Arrow SF2+

Emcraft’s 57 x 30mm SmartFusion2 module, which is also referred to as the M2S-FG484 SOM, supports a number of versions of the SmartFusion2 SoC in a FG896 package. Other features include 64MB LPDDR RAM, 16MB SPI flash, and a 10/100 Ethernet PHY. It also provides Microsemi’s LX7186A switching regulator and LX8213 LDO (low-dropout regulator).

Block diagrams: SF2+ kit (left) and Emcraft SmartFusion2 M2S-FG484 SOM details
(click image to enlarge)

Arrow’s development board for the SF2+ Development Kit adds a RJ45 Ethernet port, a USB port for power and debug, as well as a separate debug interface. Additional features include an GPIO, various serial interfaces, a power supply, an Arduino interface, and optional Arduino shields.

Emcraft M2S-FG484 SOM
(click image to enlarge)

The carrier also adds a Microsemi Timberwolf audio chip supported with 4Mb SPI flash and a pair of MEMs microphones. The Timberwolf processor offers field upgradable firmware for far field microphone, beam forming, sound location estimation, Acoustic Echo Cancellation (AEC), noise reduction and other voice enhancements, says Arrow.

Further information

The SF2+ Development Kit is available for order at $125, but is currently listed as being out of stock. More information may be found at Arrow’s SF2+ product page and Microsemi’s SF2+ product page. More on the SmartFusion2 SoC may be found at Microsemi’s SmartFusion2 product page.

Arrow is hosting a series of workshops in 2016 on the SF2+, starting with a Jan 12 event in Bloomington, Minn. Attendees will receive in-depth technical training on the SmartFusion2 SoC FPGA and step-by-step instructions on design techniques and board use. The $75 registration fee includes one SF2+ Development Kit and two ST Micro X-NUCLEO boards: the ST Micro MEMS and environmental sensor evaluation board and the ST Micro Bluetooth Low Energy evaluation board. Registration may be found here.

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One response to “IoT dev kit runs uClinux on a Microsemi Cortex-M3/FPGA SoC”

  1. Gregory O'Drobinak says:

    I would like to know when Arrow will be doing a seminar on the SF2-DEV-KIT in Chicago, Il or in Indiana.


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