Adafruit Feather nRF52840

Stuart Leitch, Moritz Salla, Yilin Zheng, Anna Tsuda, Harry Hallows, Mark Kvetny, Xiangsong Yang, Vino Chan

Use cases

• Bluetooth Low Energy and native USB support
• 'All-in-one' Arduino-compatible + Bluetooth Low Energy with built in USB plus battery charging
• Arduino IDE support
• Cortex-M4 processor
• nRF52832 projects downward compatible
• Pre-programed the chip with our UF2 bootloader

Hookup and Pins

Power Pins

• 3V: used to supply 3.3V power to external sensors, breakouts or Feather Wings
• LIPO Input (Bat): Voltage supply from the optional rechargeable cell. Can be connected via JST PH connector.
• VREG Enable (En): Can be set to GND to disable the 3.3V output. By default set to HIGH.
• USB Power (USB): Supplies voltage from USB (4.5-5.2V)

Analog Inputs

• 6 analog pins (A0–A5)
• 2 ADC pins (AREF, VIVD)

AREF (A7): optional external analog reference.
VIDV (A6): allows measurement of battery charge. Can be used as an output.

PWM Output

Any GPIO pin can be configured as PWM.

I2C Pins

• Require external pullup resistors to function. Not present by default
• All Adafruit breakouts normally have pullups, hence this likely won't be an issue

User Switches

• A general purpose switch is accessible via D7
• On board reset, press this button to force USB bootloader mode

SWD Connector

• Long header at center board
• For advanced debugging or to reprogram the board using a 1.27mm SWD cable

LEDs

There are 3 basic LEDs on the board

1. D3: general red LED. Can be used for any desired purpose. Used as a status indicator.
2. CONN: blue LED. Indicates connection status for bluetooth
3. CHG: indicates a charging battery if connected to a USB power supply

The feather has an integrated RGB light called the RGB Neo Pixel. It's color can be configured via code as PIN_NEOPIXEL. It is a good way to test if the board is setup correctly.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

SDK

Drivers

To install the drivers, you know where to go by now.

API

Arduino Bluefruit nRF52 API reference The API is class-based, with the following classes being most commonly used (from Adafruit's documentation):

• AdafruitBluefruit - the essential most-used class
• BLEService - wrapper class for BLE GATT custom services.
• BLECharacteristic - wrapper class for BLE GATT custom characteristics.
• BLEDis - helper for Device Information Services.
• BLEUart - helper for Nordic UART Service
• BLEBeacon - helper class to use the device as a Bluetooth beacon using the BT advertising packet.
• BLEMidi - helper class to use MIDI data (audio, etc) over Bluetooth.
• BLEHidAdafruit - is a helper class to emulate an HID mouse or keyboard over BLE. Related project

Languages

• C++ (the default)
• CircuitPython

IDEs

The Feather supports the usage of the Arduino IDE, but the IDE doesn't include the support out of the box. To install:

1. Download and install the Arduino IDE (At least v1.6.12)
2. Start the Arduino IDE
3. Go into Preferences
4. Add https://www.adafruit.com/package_adafruit_index.json as an 'Additional Board Manager URL'
5. Restart the Arduino IDE
6. Open the Boards Manager from the Tools -> Board menu and install 'Adafruit nRF52 by Adafruit'
7. Once the BSP is installed, select 'Adafruit Bluefruit nRF52 Feather' from the Tools -> Board menu, which will update your system config to use the right compiler and settings for the nRF52.
8. Write, compile, upload over USB.

Set up CircuitPython Quick Start

https://learn.adafruit.com/introducing-the-adafruit-nrf52840-feather/circuitpython

Board Testing

1. Select the Board Target
2. Select the USB CDC Serial Port
3. Update the bootloader (nRF52832 Feather Only)
4. Run a Test Sketch https://learn.adafruit.com/introducing-the-adafruit-nrf52840-feather/arduino-board-setup

CircuitPython for nRF53840 Download

https://circuitpython.org/board/feather_nrf52840_express/

BootLoader & Source Code

https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases/tag/0.2.13

Libraries

Adafruit nRF52 Library

• dafruit-nrfutil is based on Nordic Semiconductor ASA's pc-nrfutil
• freeRTOS as operating system
• tinyusb as usb stack
• nrfx for peripherals driver
• littlefs for internal file system

https://github.com/adafruit/Adafruit_nRF52_Arduino/tree/master/libraries

Adafruit Sponsored Libraries and Drivers from CircuitPython

https://github.com/adafruit/Adafruit_CircuitPython_Bundle/blob/master/docs/drivers.rst

Bluefruit App

Using your iOS or Android phone/tablet as a controller

A USB bootloader lets you quickly use it with the Arduino IDE or to install CircuitPython.

Sent data Format

Each Controller data packet sent is prefixed with single byte char “!” (0x21) followed by a single byte char initial for identification. Sensor data values are encoded as floats of 4 byte length.
Each packet ends with a single byte checksum for validation.

Controller Test

https://github.com/CollinCunningham/BLE_UART_Controller_Test/blob/master/BLE_UART_Controller_Test.ino

• Sensors Quaternion, Accelerometer, Gyro, Magnetometer and Location (GPS)

• 8-button Control Pad

• Colour Picker