Check out Greg Tomasch's github repository on this device.

What is it?

This is a small (18 mm x 18 mm) add-on board with Nordic's nRF52832 SoC with BLE stack, here in a form factor designed to mount directly onto a Butterfly or Teensy development board. The add-on exposes pins to connect to RX1/TX1 as well as CTS and RTS on the Butterfly board. There is a mode pin connected to an led as well to give indication when bytes are being sent or are received. The add-on takes 3V3 and GND directly from the host MCU.

The add-on board can be programmed using mbed, using a J-Link (I use the one that comes with the nRF52 Development Kit), and ST-Link, Black Magic probe, CMSIS-DAP programmer, etc. Pretty much any way you like.

The easiest way to use this add-on is to use Sandeep Mistry's nRF52 Arduino core and BLEPeripheral to program the add-on in peripheral role using Nordic's UART service. Then, when connected to your Butterfly (or Teensy) every time you do a Serial1.print on the microcontroller the bytes will be automagically transmitted via BLE from the add-on to your smart phone.

You can also program the nRF52 add-on to work in central role and, when connected to a Butterfly (Dragonfly or Teensy), the central will pair with the first BLE device it finds running Nordic's UART service and receive the byte stream being transmitted from the peripheral and send it along via USB serial to a laptop or pc. In this way, it is possible to get data streaming to your laptop Arduino IDE serial monitor from a wireless sensor node, for example.

Any remote, battery-powered Butterfly with an nRF52 add-on programmed in peripheral role using the Nordic UART service can send data via BLE to an nRF52 add-on in central role attached to a Butterfly, which is connected via USB cable to a laptop. This is a simple point-to-point gateway allowing wireless data exchange from a sensor node to your laptop. This is similar to what can be done using the ESP8285 development board and wifi, but with BLE this can be done at a fraction of the average power usage and the battery-powered sensor node can last for weeks or months using BLE compared to hours or days for wifi.

Solder a 1.25-inch insulated wire for excellent transmission and reception with a range of up to 40 meters in the open and 20 meters with obstructing walls and furniture.

The boards can come pre-programmed in peripheral role with Nordic's UART service, in central role with Nordic's UART service, or programmed with a simple blink program. Your choice. Please specify when you order.

Why did you make it?

Inexpensive, low-power, high-performance Cortex M4F MCUs that can be programmed via USB using the Arduino IDE are a fantastic tool for managing sensors and processing data. These are made even better with low-power connectivity, like that afforded by the nRF52.

The nRF52 is available as a host MCU in a variety of development boards, but these are not programmable via USB, instead requiring use of the SWD port, even though the Ardiuino core is easy enough to use. Also, the nRF52 lacks some peripherals that make the Butterfly so useful. The nRF52 I2S peripheral simply doesn't work as it should, there is no real time clock on the nRF52, there are only two low power options (sleep or deepsleep, like on the ESP8285), etc.

I wanted to combine the best of both worlds. This means an STM32L4-based host on a small development board with an nRF52 add-on for BLE connectivity. The boards come pre-programmed for either peripheral role or central role ready to serve as a UART bridge between your development board (Butterfly or Teensy) and the wired world.

I can unplug the USB cable and still receive data and diagnostic information streaming to my smart phone, tablet, or laptop using the BLE serial service and UART console. This is better than a TFT display, which has a limited amount of data that can be displayed, is attached to the remote device, and data is almost impossible to capture for analysis (I do use SPI flash and SD cards, though!). With the nRF52 add-on, I can get data remotely onto a laptop in real time for capture, storage, and later analysis, or simply to observe the real-time response of my sensor nodes. It is really convenient to be totally untethered from the sensing device and have the data show up on my workstation no matter where the sensor node happens to be (BLE has a range up to 40 meters).

What makes it special?

This is a small, inexpensive add-on that will provide your microcontroller-based projects with low-power connectivity in a compact form factor, making them ready for portable, wearable battery-powered applications.

Order the pcbs from OSH Park and assemble some of your own, or order the fully assembled and tested add-on boards from me and see how easy it is to add BLE connectivity to your embedded projects!