boards/adafruit/feather_m4_express/doc/index.rst
.. zephyr:board:: adafruit_feather_m4_express
Overview
The Adafruit Feather M4 Express is a compact, lightweight ARM development board with an onboard mini NeoPixel, 2 MiB of SPI flash, charging status indicator and user LEDs, USB connector, 21 GPIO pins and a small prototyping area.
Hardware
.. zephyr:board-supported-hw::
Zephyr can use the default Cortex-M SYSTICK timer or the SAM0 specific RTC.
To use the RTC, set :code:CONFIG_CORTEX_M_SYSTICK=n and set
:code:CONFIG_SYS_CLOCK_TICKS_PER_SEC to no more than 32 kHZ divided by 7,
i.e. no more than 4500.
The Adafruit Learning System_ has detailed information about
the board including pinouts_ and the schematic_.
The SAMD51 MCU is configured to use the 32 kHz internal oscillator with the on-chip PLL generating the 120 MHz system clock.
The SAMD51 MCU has 6 SERCOM based USARTs. On the Feather, SERCOM5 is the Zephyr console and is available on pins 0 (RX) and 1 (TX).
The SAMD51 MCU has 6 SERCOM based SPIs. On the Feather, SERCOM1 can be put into SPI mode and used to connect to devices over the SCK (SCLK), MO (MOSI), and MI (MISO) pins.
The SAMD51 has three PWM generators with up to six channels each. :code:TCC_0
has a resolution of 24 bits and all other generators are 16 bit. :code:TCC_1
pin 2 is mapped to PA18 (D7) and pin 3 is mapped to PA19 (D9).
The SAMD51 MCU has a USB device port that can be used to communicate
with a host PC. See the :ref: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.
Programming and Debugging
.. zephyr:board-supported-runners::
The Feather ships with a the BOSSA compatible UF2 bootloader. The bootloader can be entered by quickly tapping the reset button twice.
Additionally, if :kconfig:option:CONFIG_USB_CDC_ACM is enabled then the
bootloader will be entered automatically when you run :code:west flash.
#. Build the Zephyr kernel and the :zephyr:code-sample:hello_world sample application:
.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: adafruit_feather_m4_express :goals: build :compact:
#. Connect the feather 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:
#. Tap the reset button twice quickly to enter bootloader mode
#. Flash the image:
.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: adafruit_feather_m4_express :goals: flash :compact:
You should see "Hello World! adafruit_feather_m4_express" in your terminal.
In addition to the built-in bootloader, the Feather can be flashed and debugged using a SWD probe such as the Segger J-Link.
#. Connect the board to the probe by connecting the :code:SWCLK,
:code:SWDIO, :code:RESET, :code:GND, and :code:3V3 pins on the
Feather to the :code:SWCLK, :code:SWDIO, :code:RESET, :code:GND,
and :code:VTref pins on the J-Link_.
#. Flash the image:
.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: adafruit_feather_m4_express :goals: flash :flash-args: -r openocd :compact:
#. Start debugging:
.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: adafruit_feather_m4_express :goals: debug :compact:
References
.. target-notes::
.. _Adafruit Learning System: https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51
.. _pinouts: https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51/pinouts
.. _schematic: https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51/downloads
.. _J-Link: https://www.segger.com/products/debug-probes/j-link/technology/interface-description/