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.

XIAO BLE

Overview

The Seeed XIAO BLE is a tiny (21 mm x 17.5 mm) Nordic Semiconductor nRF52840 ARM Cortex-M4F development board with onboard LEDs, USB port, QSPI flash, battery charger, and range of I/O broken out into 14 pins.

XIAO BLE

Hardware

  • Nordic nRF52840 Cortex-M4F processor at 64MHz

  • 2MB QSPI Flash

  • RGB LED

  • USB Type-C Connector, nRF52840 acting as USB device

  • Battery charger BQ25101

  • Reset button

  • Bluetooth antenna

Supported Features

The xiao_ble board configuration supports the following hardware features:

Interface

Controller

Driver/Component

ADC

on-chip

adc

CLOCK

on-chip

clock_control

FLASH

on-chip

flash, QSPI flash

GPIO

on-chip

gpio

I2C(M)

on-chip

i2c

MPU

on-chip

arch/arm

NVIC

on-chip

arch/arm

PWM

on-chip

pwm

RADIO

on-chip

Bluetooth, ieee802154

RTC

on-chip

system clock

SPI(M/S)

on-chip

spi

UART

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 XIAO BLE wiki 1 has detailed information about the board including pinouts 2 and the schematic 3.

LED

  • LED1 (red) = P0.26

  • LED2 (green) = P0.30

  • LED3 (blue) = P0.06

Programming and Debugging

The XIAO BLE ships with the Adafruit nRF52 Bootloader 5 which supports flashing using UF2 6. Doing so allows easy flashing of new images, but does not support debugging the device. For debugging please use External Debugger.

UF2 Flashing

To enter the bootloader, connect the USB port of the XIAO BLE to your host, and double tap the reset botton to the left of the USB connector. A mass storage device named XIAO BLE should appear on the host. Using the command line, or your file manager copy the zephyr/zephyr.uf2 file from your build to the base of the XIAO BLE mass storage device. The XIAO BLE will automatically reset and launch the newly flashed application.

External Debugger

In order to support debugging the device, instead of using the bootloader, you can use an External Debug Probe. To flash and debug Zephyr applications you need to use Seeeduino XIAO Expansion Board 4 or solder an SWD header onto the back side of the board.

For Segger J-Link debug probes, follow the instructions in the J-Link External Debug Probe page to install and configure all the necessary software.

Flashing

Follow the instructions in the J-Link External Debug Probe page to install and configure all the necessary software. Then build and flash applications as usual (see Building an Application and Run an Application for more details).

Here is an example for the Hello World application.

First, run your favorite terminal program to listen for output.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the port where the board XIAO BLE can be found. For example, under Linux, /dev/ttyACM0.

Then build and flash the application in the usual way. Just add CONFIG_BOOT_DELAY=5000 to the configuration, so that USB CDC ACM is initialized before any text is printed, as below:

# From the root of the zephyr repository
west build -b xiao_ble samples/hello_world -- -DCONFIG_BOOT_DELAY=5000
west flash

Debugging

Refer to the J-Link External Debug Probe page to learn about debugging boards with a Segger IC.

Testing the LEDs in the XIAO BLE

There is a sample that allows to test that LEDs on the board are working properly with Zephyr:

# From the root of the zephyr repository
west build -b xiao_ble samples/basic/blinky
west flash

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

Testing shell over USB in the XIAO BLE

There is a sample that allows to test shell interface over USB CDC ACM interface with Zephyr:

# From the root of the zephyr repository
west build -b xiao_ble samples/subsys/shell/shell_module
west flash

References

1

https://wiki.seeedstudio.com/XIAO_BLE/

2

https://wiki.seeedstudio.com/XIAO_BLE/#hardware-overview

3

https://wiki.seeedstudio.com/XIAO_BLE/#resources

4

https://wiki.seeedstudio.com/Seeeduino-XIAO-Expansion-Board/

5

https://github.com/adafruit/Adafruit_nRF52_Bootloader

6

https://github.com/microsoft/uf2