This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

CX1825 nRF52840


Croxel’s CX1825 Bluetooth Prototyping board [1] provides support for the Nordic Semiconductor nRF52840 ARM Cortex-M4F CPU and the following devices:

  • ADC



  • GPIO

  • I2C

  • MPU

  • NVIC

  • PWM

  • RADIO (Bluetooth Low Energy and 802.15.4)

  • RTC

  • Segger RTT (RTT Console)

  • SPI

  • USB

  • WDT


Croxel’s CX1825 Bluetooth Prototyping board (Credit: Croxel)


  • Ezurio’s BL654 (nRF52840 ARM Cortex-M4F processor at 64MHz)

  • 1 MB flash memory and 256 KB of SRAM

  • Coin-cell retainer for Lithium coincell batteries

  • 2 Discrete LEDs (Red and Green)

  • User Button

  • Reset Button

  • Accelerometer (LIS3DH)

  • Ambient & RGB Light and Proximity Sensor (APDS9960)

  • Temperature and Humidity Sensor (HTS221)

  • Barometric Pressure sensor (LPS22H)

  • Hall Effect Switch (MLX90248)

  • RGB LED with Charge-Pump driver (LPS5521)

  • Digital Microphone

  • Beeper

  • QWIIC connector supporting expansion for I2C devices

  • USB Connector for data and power

  • 16-pin Expansion connector

  • SWD Connector

Supported Features

  • Discrete LEDs (red and green)

  • Buttons (User and Reset)

  • Sensors (Accelerometer, Light, Temperature and Humidity, Pressure and Hall-Effect sensors)

  • Beeper

  • Radio (Bluetooth, IEEE 802.15.4)

  • SOC peripherals (ADC, Clock, Flash, GPIO, I2C, MPU, NVIC, PWM, Radio, RTC, SPI, USB, WDT)

Future Feature Support

  • RGB LED (Charge-Pump driver not implemented)

  • Microphone

Connections and IOs

Croxel’s CX1825 Bluetooth Prototyping board has detailed information about the board (schematic [2])


  • LED1 (red) = P0.8

  • LED2 (green) = P0.12

Digital Inputs

  • User Button = P1.16

  • Reset Button = P0.18

  • Hall-Effect Switch = P0.15

Programming and Debugging

Applications for the croxel_cx1825/nrf52840 board configuration can be built and flashed in the usual way (see Building an Application and Run an Application for more details).


Flashing Zephyr onto the croxel_cx1825_nrf52840 board requires an external programmer. The programmer is attached to the SWD header.

Build the Zephyr kernel and the Blinky sample application.

west build -b croxel_cx1825/nrf52840 samples/basic/blinky

Flash the image.

west build -b croxel_cx1825/nrf52840 samples/basic/blinky
west flash

You should see the red LED blink.