ItsyBitsy nRF52840

Overview

The Adafruit ItsyBitsy nRF52840 Express is a small (36 mm x 18 mm) ARM development board with an onboard RGB LED, USB port, 2 MB of QSPI flash, and range of I/O broken out onto 21 GPIO pins.

This development kit has the following features:

  • ADC

  • CLOCK

  • FLASH

  • GPIO

  • I2C

  • I2S

  • MPU

  • NVIC

  • PWM

  • QSPI

  • RADIO (Bluetooth Low Energy and 802.15.4)

  • RTC

  • SPI

  • UARTE

  • USB

  • WDT

Hardware

  • nRF52840 ARM Cortex-M4F CPU at 64MHz

  • 1 MB of flash memory and 256 KB of SRAM

  • 2 MB of QSPI flash

  • A user LED

  • A user switch

  • An RGB DotStar LED

  • Native USB port

  • One reset button

Supported Features

The Adafruit ItsyBitsy nRF52840 board configuration supports the following hardware features:

Interface

Controller

Driver/Component

ADC

on-chip

adc

CLOCK

on-chip

clock_control

FLASH

on-chip

flash

GPIO

on-chip

gpio

I2C

on-chip

i2c

MPU

on-chip

arch/arm

NVIC

on-chip

arch/arm

PWM

on-chip

pwm

QSPI(M)

on-chip

nor

RADIO

on-chip

Bluetooth, ieee802154

RTC

on-chip

system clock

SPI

on-chip

spi

UARTE

on-chip

serial

USB

on-chip

usb

WDT

on-chip

watchdog

Other hardware features have not been enabled yet for this board.

Connections and IOs

The Adafruit ItsyBitsy nRF52840 Express Learn site [1] has detailed information about the board including pinouts [2] and the schematic [3].

LED

  • LED0 (red) = P0.06

  • LED1 (Adafruit DotStar)

    • DATA = P0.08

    • CLK = P1.09

Push buttons

  • SWITCH = P0.29

  • RESET = P0.18

Logging

Logging is done using the USB-CDC port. See the Logging sample or the Console over USB CDC ACM sample applications to see how this works.

Testing LEDs and buttons on the Adafruit ItsyBitsy nRF52840 Express

The Button sample lets you test the buttons (switches) and the red LED. The Blinky sample lets you test the red LED.

The DotStar LED has been implemented as a SPI device and can be tested with the LED strip sample application.

You can build and flash the examples to make sure Zephyr is running correctly on your board. The button and LED definitions can be found in boards/adafruit/itsybitsy/adafruit_itsybitsy_nrf52840.dts.

Programming and Debugging

The ItsyBitsy ships with the BOSSA compatible UF2 bootloader. The bootloader can be entered by quickly tapping the reset button twice.

First time setup

Some versions of this board were shipped with a buggy bootloader. Ensure that the bootloader is up to date by following the Adafruit UF2 Bootloader update [4] tutorial. Note that this tutorial was made for the Adafruit Feather nRF52840, but the steps to update the bootloader are the same for the ItsyBitsy. The files for the ItsyBitsy bootloader can be found in the Adafruit nRF52 Bootloader repo [5].

The building and flashing of Zephyr applications have been tested with release 0.7.0 of the UF2 bootloader.

Flashing

Flashing is done by dragging and dropping the built Zephyr UF2-file into the ITSY840BOOT drive.

  1. Build the Zephyr kernel and the Blinky sample application:

    west build -b adafruit_itsybitsy/nrf52840 samples/basic/blinky

  2. Connect the ItsyBitsy to your host computer using USB

  3. Tap the reset button twice quickly to enter bootloader mode

  4. Flash the image:

    Drag and drop the file samples/basic/blinky/build/zephyr/zephyr.uf2 into ITSY840BOOT

The device will disconnect and you should see the red LED blink.

References