Design App With Bluefruit Le Board

Two Cortex-M4 Bluetooth LE boards have gained wider distribution: Arrow is selling SensiEdge's SensiBLE, and Mouser has Adafruit's Feather Nrf52 Bluefruit.

Bluetooth Low Energy (BLE) continues to rise in importance as the wireless conduit for MCU-based IoT edge devices. Late last week Arrow Electronics announced it was launching the recently introduced SensiBLE IoT SoM, which is also referred to as the Simba-Pro, from Israel-based SensiEdge. (Mouser has already begun distributing the product, as has RS Components in the UK.)

SensiBLE IoT SoM (left) and Feather Nrf52 Bluefruit
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Meanwhile, Mouser said it would expand the reach of Adafruit's Arduino compatible Feather Nrf52 Bluefruit, which launched in March (see farther below). Both boards combine Cortex-M4 based MCUs with BLE support and other I/O squeezed onto tiny footprints. The SensiBLE board offers higher end features at almost three times the price of the Feather Nrf52 Bluefruit, and provides optional development boards.

SensiEdge's SensiBLE

The 30 x 20mm SensiBLE computer-on-module, also called the Simba-Pro, was originally unveiled last year as a collaboration between STMicroelectronics and SensiEdge. The $70 module is being promoted by ST as being fully compatible with its STM32 Nucleo boards and X-Nucleo ecosystem, offering similar functionality in a much smaller form factor.

SensiBLE IoT SoM with coin cell holder (left) and detail view
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The module offers Bluetooth 4.1 LE connectivity, as well as sensors for pressure, temperature, humidity, and ambient light. There's also a 3-axis accelerometer, magnetometer and digital gyroscope.

SensiBLE IoT SoM compared to Nucleo boards
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The SensiBLE provides the equivalent of an STM32 Nucleo combined with several X-Nucleo add-on boards: an X-Nucleo-IDB05A1 BLE module, an X-Nucleo-IKS01A1 sensor module, and an X-Nucleo-CCA02M1 digital mic module. In addition, the SensiBLE provides extras like a data logger, buzzer, and light/color detection sensor.

SensiBLE architecture
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The SensiBLE is equipped with the same Cortex-M4-based STM32L476 MCU found on the STM32 Nucleo. The MCU is also found on ST's 14 x 14mm, Arduino-compatible SensorTile sensor and BLE module, which offers many, but not all the features of the larger SensiBLE. The 32-bit, 80MHz STM32L476 is less powerful than the 180MHz STM32F469BI model found on the Arduino STAR Otto. The STAR Otto, a collaboration between ST with Arduino Srl, is compatible with several STM32 Nucleo expansion boards and software libraries.

The SensiBLE provides a USB interface, as well as I/O including GPIO I2C, SPI, SDIO, ADC, PWM, UART, and CAN. The module includes a user button and LED, and is available with a coin cell battery slot. It runs on 1.7V to 3.6V power, and supports -40 to 85°C temperatures.

Simplified (left) and detailed SensiBLE block diagrams
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The SensiBLE supports the same BlueNRG-MS drivers and BlueST-SDK found on the STM Nucleo. The SDK lets you create Android and iOS apps that interact directly with the board's sensors, and offers functions such as real-time activity recognition and motion sensor data fusion. It also supports real-time pedometer and gesture recognition, as well as a "carry position detection algorithm."

The module can be used with the IBM Watson IoT framework together with IBM Bluemix. Other supported development platforms include ARM's Mbed OS and Keil tools. A SensiBLE demo app is available for Android.

Simba-DKL (left) and Simba-DKJ
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The SensiBLE IoT SoM will be available with one of two Arduino shield compatible development kits, both with USB ports: a standard Simba-DKL debugging board and a JTAG-ready Simba-DKJ board. Like the module, the development boards ships with schematics and mechanical drawings, and the module is also available with a 3D STEP model. No pricing or further details appeared to be available on the carrier boards.

Adafruit's Feather nRF52 Bluefruit LE

The Feather nRF52 Bluefruit LE, which is now available from Mouser for $22.46, arrived this spring as the latest member of Adafruit's Bluetooth oriented Feather Bluefruit family. These include the Feather M0 Bluefruit which combines a ATSAMD21G18 (Cortex-M0) MCU with a nRF51822 BLE chip.

Feather nRF52 Bluefruit LE side view (left) and with battery and breadboard
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The new board runs on a more advanced, 64MHz Nordic Nrf52, an Arduino IDE-compatible Cortex-M4F MCU with onboard 2.4GHz BLE. The Nrf52 has also appeared on the Arduino Primo SBC and Primo Core module, as well as Pure Engineering's PUREmodules kit, among others.

The FPU-equipped Nrf52832 MCU provides the Feather nRF52 Bluefruit LE with twice the flash memory (512KB), RAM (64KB), and performance of the earlier, nRF51-equipped Feather Bluefruits. Its BLE transceiver offers transmit power up to 4 dBm and receiver sensitivity of -96 dBm in BLE mode.

The 51 x 23mm, 5.7-gram board supports applications including IoT, wearables, lighting, and MIDI audio. Features include 19x GPIOs, 8x 12-bit analog inputs, and 3x 4-output PWM interfaces.

Feather nRF52 Bluefruit LE rear view
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The Feather nRF52 Bluefruit LE provides a micro-USB port with a USB-to-serial converter for debugging. A lithium polymer battery connector provides onboard USB-based battery charging at 1.7V to 3.3V. There's also a reset button and 4x mounting holes. An auto-resetting bootloader streamlines Arduino IDE programming, and command tools are available that tap into the optional SWD connector.

Further information

SensiEdge's SensiBLE is now available at Arrow Electronics for $70. It's also available at Mouser for $63 and at RS Components for 46 Pounds. More information may be found at ST's SensiBLE page and at the SensiEdge website.

Adafruit's Feather nRF52 Bluefruit LE is now available at Mouser for $22.46 ($20 for 10+ units) or at Adafruit for $24.95.