.. _xiao_ble:

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.

.. figure:: img/xiao_ble.png
     :width: 300px
     :align: center
     :alt: 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`_ has detailed information about the board including
`pinouts`_ and the `schematic`_.

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`_ which supports flashing
using `UF2`_. 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 :ref:`External Debug Probe <debug-probes>`. To flash and debug Zephyr
applications you need to use `Seeeduino XIAO Expansion Board`_ or solder an SWD
header onto the back side of the board.

For Segger J-Link debug probes, follow the instructions in the
:ref:`jlink-external-debug-probe` page to install and configure all the
necessary software.

Flashing
--------

Follow the instructions in the :ref:`jlink-external-debug-probe` page to install
and configure all the necessary software. Then build and flash applications as
usual (see :ref:`build_an_application` and :ref:`application_run` for more
details).

Here is an example for the :ref:`hello_world` application.

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

.. code-block:: console

   $ minicom -D <tty_device> -b 115200

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

.. zephyr-app-commands::
   :zephyr-app: samples/hello_world
   :board: xiao_ble
   :goals: build flash
   :gen-args: -DCONFIG_BOOT_DELAY=5000

Debugging
---------

Refer to the :ref:`jlink-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:

.. zephyr-app-commands::
   :zephyr-app: samples/basic/blinky
   :board: xiao_ble
   :goals: build 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
:zephyr_file:`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:

.. zephyr-app-commands::
   :zephyr-app: samples/subsys/shell/shell_module
   :board: xiao_ble
   :goals: build flash

References
**********

.. target-notes::

.. _XIAO BLE wiki: https://wiki.seeedstudio.com/XIAO_BLE/
.. _pinouts: https://wiki.seeedstudio.com/XIAO_BLE/#hardware-overview
.. _schematic: https://wiki.seeedstudio.com/XIAO_BLE/#resources
.. _Seeeduino XIAO Expansion Board: https://wiki.seeedstudio.com/Seeeduino-XIAO-Expansion-Board/
.. _Adafruit nRF52 Bootloader: https://github.com/adafruit/Adafruit_nRF52_Bootloader
.. _UF2: https://github.com/microsoft/uf2