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(get email updates) goes Cortex-M4 with IoT Edition and Carbon SBC

Sep 27, 2016 — by Eric Brown — 1,655 views
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Linaro,, and SeeedStudio have launched the first 96Boards IoT Edition SBC — a $28 BLE-ready “BLE Carbon” that runs Zephyr on an ST Cortex-M4.

Linaro Ltd and its open hardware standardization group announced the first non-Linux and MCU based 96Boards single board computer, and the first to comply with a new 96Boards IoT Edition (IE) spec. Built by SeeedStudio, and designed with the help of Linaro, the flagship IE board is called “Carbon” by Linaro and 96Boards, and is called “BLE Carbon” by SeeedStudio. This suggests there might be other Carbon variants in the offing that could feature other radios in addition to, or in place of, the Carbon BLE’s Bluetooth Low Energy function.

BLE Carbon, front and back
(click images to enlarge)

The BLE Carbon SBC is also the first SBC to run the Linux Foundation’s Intel-backed Zephyr open source RTOS. The lightweight OS runs on an STMicroelectronics STM32F401RE processor built around an 84MHz Cortex-M4 core, along with 96KB SRAM and 512KB flash (see additional BLE Carbon details farther below). The Carbon IoT reference board is targeted at “IoT and embedded developers, the hobby community, and the open-source community,” says Linaro.

Linaro, which is owned by ARM and major ARM licensees, and which develops open source software for ARM devices, also launched a Linaro IoT and Embedded (LITE) initiative. Both and LITE will support Carbon and other future 96Boards IE hardware including RTOS-driven Cortex-M and -R boards and Linux-based Cortex-A boards. Carbon, 96Boards IE, and LITE were all announced at this week’s Linaro Connect event in Las Vegas.

96Boards IoT Edition spec

The 96Boards IE spec is available in the “Standard Micro” 60 x 30 x 9mm form-factor used by the Carbon, as well in an “Extended” 85 x 54 x 12mm format. Both versions use a single 30-pin low speed expansion connector.

Dimensions for 96Boards IE Standard Micro (left) and Extended form-factors with 3.3V power. (See documentation from 96Boards link at end for 1.8V standard version as well as pin assignments for all three.)
(click images to enlarge)

By comparison, there are both 40-pin low speed and 60-pin high speed connectors on the original 96Boards Consumer Edition spec that was used by the HiKey, DragonBoard 410c, Bubblegum-96, and others. The Enterprise Edition used by the LeMaker Cello has 60-pin high speed and PCIe x16 interfaces.

Comparison of 96Boards IE Extended (left) and 96Boards CE Standard form-factors
(click images to enlarge)

The 96Boards IE spec further requires a micro-USB or USB Type C port for 5V power and host/slave serial communication. A second port of either type is optional for an FTDI-style UART bringup/debug console, and is recommended if you’re using the USB for power.

Optionally, you can assign bringup/debug to a UART on the expansion connector or another specified header. Maximum power consumption cannot exceed the USB power limit. Power and user LEDs are also required, as well as a wireless LED if a radio is present.

The spec strongly recommends at least one low-power wireless interface or a USB Type A or C port that supports wireless USB dongles. For wireless, 96Boards mentions BLE, ZigBee, 6LowPAN, and LoRaWAN, but it does not appear that these are the only options. WiFi is mentioned elsewhere as an option.

If you want to add microSD or CSI camera interfaces, there are specified locations and pin pitch size requirements, respectively. 96Boards IE board designers can add additional components such as sensors, controllers, and additional wireless and industrial network interfaces.

The spec supports 32- or 64-bit SoCs in one of two profiles: Cortex R/M and Cortex-A. On the Cortex R/M profile, minimums of 32KB RAM and 128KB bootable flash (including on-SoC memory) are strongly recommended, while on the Linux-oriented Cortex-A profile, the spec suggests at least 512MB RAM (including PoP-mounted RAM) and 512MB bootable eMMC. There are no clock speed limits.

Additionally, as indicated by the above pair of dimension drawings, a single carrier board can be designed to except a choice of either Standard Micro or Extended form-factor boards.

BLE Carbon

The flagship 96Boards IE board is SeeedStudio’s BLE Carbon. The 60 x 30mm SBC is preloaded with the open source Zephyr RTOS, which runs on ST’s STM32F401, at up to 84MHz Cortex-M4 SoC that integrates 96KB RAM and 512KB flash. According to ST, when executing from flash, the SoC delivers 105 DMIPS/285 CoreMark performance, with offers run mode consumption as low as 128 µA/MHz.

BLE Carbon
(click image to enlarge)

The BLE Carbon’s Bluetooth LE radio is enabled with a Nordic Semiconductor nRF51822 SoC. The chip integrates a Cortex M0 with 32KB/16KB RAM and 256KB/128KB flash. Flashing the nRF51822 chip requires an SWD programmer such as an ST-Linkv2 or Segger JLink.

BLE Carbon pin assignments
(click image to enlarge)

The BLE Carbon features two micro-USB ports, one of which is used for power, and has the required 30-pin low-speed connector. Analog pins and debug connectors are also onboard. You also get 6x LEDs, as well as reset and boot buttons.

Specifications listed for the BLE Carbon include:

  • Processor — ST STM32F401 (1x Cortex-M4 @ up to 84MHz)
  • Memory (via STM32F401) — 96KB RAM; 512KB flash
  • Wireless — Bluetooth LE (2.4GHz nRF51822); chip antenna
  • Other I/O:
    • 2x micro-USB ports (1x for power)
    • 6x analog pins
    • SWD debug connectors
    • 30-pin (2 x 15-pin 2.54mm pitch) low-speed expansion connector (+3.3V, +5V, VCC, GND, UART, I2C, SPI, 4x GPIO)
  • Other features — 6x LEDs (UART Tx and Rx, power, BT, 2x user); reset and boot buttons
  • Power — Micro-USB based with fuse protect; 3.3V digital out; 0-3.3V analog in
  • Dimensions — 60 x 30mm
  • Operating system — Zephyr

Further information

The BLE Carbon SBC is available from SeeedStudio for pre-order for $27.95, with shipments expected on Oct. 20. More details may be found at SeedStudio’s BLE Carbon shopping page and BLE Carbon wiki, as well as at’s Carbon product page. More on 96Boards IoT Edition may be found at

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