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Overview

boards/seeed/seeeduino_xiao/doc/index.rst

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.. zephyr:board:: seeeduino_xiao

Overview

The Seeeduino XIAO is a tiny (20 mm x 17.5 mm) ARM development board with onboard LEDs, USB port, and range of I/O broken out onto 14 pins.

Hardware

  • ATSAMD21G18A ARM Cortex-M0+ processor at 48 MHz
  • 256 KiB flash memory and 32 KiB of RAM
  • Three user LEDs
  • Native USB port

Supported Features

.. zephyr:board-supported-hw::

Connections and IOs

The Seeeduino XIAO wiki_ has detailed information about the board including pinouts_ and the schematic_.

System Clock

The SAMD21 MCU is configured to use the 32 kHz external crystal with the on-chip PLL generating the 48 MHz system clock. The internal APB and GCLK unit are set up in the same way as the upstream Arduino libraries.

SPI Port

The SAMD21 MCU has 6 SERCOM based SPIs. On the XIAO, SERCOM0 can be put into SPI mode and used to connect to devices over pin 9 (MISO), pin 10 (MOSI), and pin 8 (SCK).

I2C Port

The SAMD21 MCU has 6 SERCOM based USARTs. On the XIAO, SERCOM2 is available on pin 4 (SDA) and pin 5 (SCL).

Serial Port

The SAMD21 MCU has 6 SERCOM based USARTs. On the XIAO, SERCOM4 is the Zephyr console and is available on pins 7 (RX) and 6 (TX).

USB Device Port

The SAMD21 MCU has a USB device port that can be used to communicate with a host PC. See the :zephyr:code-sample-category:usb sample applications for more, such as the :zephyr:code-sample:usb-cdc-acm sample which sets up a virtual serial port that echos characters back to the host PC.

DAC

The SAMD21 MCU has a single channel DAC with 10 bits of resolution. On the XIAO, the DAC is available on pin 0.

Programming and Debugging

.. zephyr:board-supported-runners::

The XIAO ships the BOSSA compatible UF2 bootloader. The bootloader can be entered by shorting the RST and GND pads twice.

Additionally, if :code:CONFIG_USB_CDC_ACM is enabled then the bootloader will be entered automatically when you run :code:west flash.

Flashing

#. Build the Zephyr kernel and the :zephyr:code-sample:hello_world sample application:

.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: seeeduino_xiao :goals: build :compact:

#. Connect the XIAO to your host computer using USB

#. Connect a 3.3 V USB to serial adapter to the board and to the host. See the Serial Port_ section above for the board's pin connections.

#. Run your favorite terminal program to listen for output. Under Linux the terminal should be :code:/dev/ttyUSB0. For example:

.. code-block:: console

  $ minicom -D /dev/ttyUSB0 -o

The -o option tells minicom not to send the modem initialization string. Connection should be configured as follows:

  • Speed: 115200
  • Data: 8 bits
  • Parity: None
  • Stop bits: 1

#. Short the RST and GND pads twice quickly to enter bootloader mode

#. Flash the image:

.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: seeeduino_xiao :goals: flash :compact:

You should see "Hello World! seeeduino_xiao" in your terminal.

References

.. target-notes::

.. _Seeeduino XIAO wiki: https://wiki.seeedstudio.com/Seeeduino-XIAO/ .. _pinouts: https://wiki.seeedstudio.com/Seeeduino-XIAO/#hardware-overview .. _schematic: https://wiki.seeedstudio.com/Seeeduino-XIAO/#resources