board support: added support for the Seeed Studio XIAO SAMD21 board

Documentation/platforms/arm/samd2l2/boards/xiao-seeeduino/index.rst

@@ -0,0 +1,138 @@
+========================
+Seeed Studio Xiao SAMD21
+========================
+
+The `Seeed Studio Xiao SAM21 <https://wiki.seeedstudio.com/Seeeduino-XIAO/>`_ is the first of the XIAO family, and is a
+general purpose, low-power and tiny board. It can be referred to as the "Seeed Studio Xiao SAMD21" or the "Xiao
+Seeeduino".
+
+.. figure:: seeed-xiao-samd21.jpg
+   :align: center
+
+Features
+========
+
+* ATSAMD21G18A-MU microcontroller chip @48MHz
+* 256KB flash
+* 32KB SRAM
+* 14 pins (11 analog, 11 digital)
+* 10 PWM interfaces
+* 1 DAC output pin
+* Serial wire debug interface
+* 1 I2C interface
+* 1 SPI interface
+* 1 UART interface
+* USBC interface
+* Serial communication indicator LEDs for TX and RX (blue)
+* Power indicator LED (green)
+* Blinkable LED (yellow)
+
+Serial Console
+==============
+
+By default, the serial console appears on the board's UART interface. Pin 9 is
+TX and pin 7 is RX.
+
+Pin Mapping
+===========
+
+Pins are numbered anticlockwise from the USB connector.
+
+===== ======== ========================================
+Pin   Signal   Notes
+===== ======== ========================================
+0     PA2      A0/D0/DAC
+1     PA4      A1/D1
+2     PA10     A2/D2
+3     PA11     A3/D3
+4     PA8      A4/D4/SDA (I2C)
+5     PA9      A5/D5/SCL (I2C)
+6     PB08     A6/D6/TX (UART)
+7     PB09     A7/D7/RX (UART)
+8     PA7      A8/D8/SCK (SPI)
+9     PA5      A9/D9/MISO (SPI)
+10    PA6      A10/D10/MOSI (SPI)
+11    3V3
+12    GND
+13    5V       You can supply 5V power on this pin too.
+===== ======== ========================================
+
+There are also four pads on the back side of the board. SWCLK, SWDIO for serial
+wire debugging, and RST and GND for resetting the board. These same two pins are
+also exposed on the top of the board.
+
+Power Supply
+============
+
+The board can be powered through a USB-C connection. It can also be supplied 5V
+power through it's 5V power pin.
+
+There is an additional two pads for powering the board (VIN and GND) on the back
+side. The board accepts anywhere between 3.3V and 5V.
+
+Installation
+============
+
+To build NuttX for the Xiao Seeduino, you can use the following configuration
+commands within the cloned ``nuttx`` repository:
+
+.. code-block:: console
+
+   $ ./tools/configure.sh xiao-seeeduino:nsh
+   $ make
+
+This will generate a ``nuttx.hex`` file. To put the program on your board, you
+can choose from one of the following:
+
+1. Convert the hex file to a uf2 file using the `Microsoft uf2 tool <https://github.com/microsoft/uf2/>`_:
+
+   .. code-block:: console
+
+      $ git clone https://github.com/microsoft/uf2.git
+      $ cd uf2/utils
+      $ python uf2conv.py -f 0x68ed2b88 -b 0x2000 nuttx.hex -o nuttx.uf2
+
+   Then, plug your board into the host computer using the USB-C interface. Short
+   the RST (reset) pad with ground twice in a row quickly. The board will be
+   detected as mass storage under the name "Arduino", and its orange LED will be
+   pulsing slowly. You can then copy the UF2 file to the drive/storage device
+   which appears. Once the file is done copying, the board will auto-eject and
+   you will have an NSH console on the UART pins!
+
+   .. todo::
+      Maybe this process should be part of the post-build scripts, since the
+      Microsoft UF2 tools is MIT licensed.
+
+2. Flash the hex file using the ``bossac`` tool. You can find the source for it
+   `here <https://github.com/shumatech/BOSSA/>`_, or you can install it on Arch
+   Linux via the AUR with this command:
+
+   .. code-block:: console
+      
+      $ yay -S bossa
+
+   Then, plug your Seeduino in via USB-C to the host computer and short the RST
+   (reset) and ground pins twice in a row quickly. The board will be detected as
+   mass storage under the name "Arduino", and its orange LED should be pulsing.
+   You can then run the following command:
+
+   .. code-block:: console
+
+      $ sudo stty -F <path/to/xiao-USB-port> 1200
+      $ sudo bossac -i -d --port=<path/to/xiao-USB-port> -i -w -v nuttx.hex -R
+
+   .. todo::
+      The ``bossac`` utility doesn't actually work for programming in my testing
+      yet. It is what the Arduino IDE uses but I haven't managed to get the
+      commmand line working. Using the commands listed above does actually
+      detect the board but the programming itself fails with "Flash command
+      failed". This needs more debugging.
+
+Configurations
+==============
+
+nsh
+---
+
+Basic NuttShell configuration with the console enabled on the UART interface at
+115200 bps. Comes with "Hello world" demo.

boards/Kconfig

@@ -2329,6 +2329,15 @@ config ARCH_BOARD_SAMD21_XPLAINED
 		This board features the ATSAMD21J18A MCU (Cortex-M0+ with 256KB of FLASH
 		and 32KB of SRAM).
 
+config ARCH_BOARD_XIAO_SEEEDUINO
+	bool "Seeed Studio XIAO SAMD21"
+	depends on ARCH_CHIP_SAMD21J18A
+	select ARCH_HAVE_LEDS
+	---help---
+		The port of NuttX to the Seeed Studio XIAO SAMD21 board.
+		This board features the ATSAMD21J18A MCU (Cortex-M0+ with 256KB of FLASH
+		and 32KB of SRAM) in a tiny footprint.
+
 config ARCH_BOARD_SAME54_XPLAINED_PRO
 	bool "Atmel SAME54-Xplained Pro development board"
 	depends on ARCH_CHIP_SAME54P20
@@ -3467,6 +3476,7 @@ config ARCH_BOARD
 	default "sama5d4-ek"                if ARCH_BOARD_SAMA5D4_EK
 	default "samd20-xplained"           if ARCH_BOARD_SAMD20_XPLAINED
 	default "samd21-xplained"           if ARCH_BOARD_SAMD21_XPLAINED
+	default "xiao-seeeduino"            if ARCH_BOARD_XIAO_SEEEDUINO
 	default "same54-xplained-pro"       if ARCH_BOARD_SAME54_XPLAINED_PRO
 	default "saml21-xplained"           if ARCH_BOARD_SAML21_XPLAINED
 	default "sam3u-ek"                  if ARCH_BOARD_SAM3UEK
@@ -3945,6 +3955,9 @@ endif
 if ARCH_BOARD_SAMD21_XPLAINED
 source "boards/arm/samd2l2/samd21-xplained/Kconfig"
 endif
+if ARCH_BOARD_XIAO_SEEEDUINO
+source "boards/arm/samd2l2/xiao-seeeduino/Kconfig"
+endif
 if ARCH_BOARD_SAME54_XPLAINED_PRO
 source "boards/arm/samd5e5/same54-xplained-pro/Kconfig"
 endif

boards/arm/samd2l2/xiao-seeeduino/Kconfig

@@ -0,0 +1,12 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+if ARCH_BOARD_XIAO_SEEEDUINO
+
+menu "XIAO Seeeduino"
+
+endmenu # XIAO Seeeduino
+
+endif # ARCH_BOARD_XIAO_SEEEDUINO

boards/arm/samd2l2/xiao-seeeduino/configs/nsh/defconfig

@@ -0,0 +1,59 @@
+#
+# This file is autogenerated: PLEASE DO NOT EDIT IT.
+#
+# You can use "make menuconfig" to make any modifications to the installed .config file.
+# You can then do "make savedefconfig" to generate a new defconfig file that includes your
+# modifications.
+#
+# CONFIG_DISABLE_POSIX_TIMERS is not set
+# CONFIG_NSH_DISABLEBG is not set
+# CONFIG_NSH_DISABLESCRIPT is not set
+# CONFIG_NSH_DISABLE_CMP is not set
+# CONFIG_NSH_DISABLE_DD is not set
+# CONFIG_NSH_DISABLE_EXEC is not set
+# CONFIG_NSH_DISABLE_EXIT is not set
+# CONFIG_NSH_DISABLE_GET is not set
+# CONFIG_NSH_DISABLE_HEXDUMP is not set
+# CONFIG_NSH_DISABLE_IFCONFIG is not set
+# CONFIG_NSH_DISABLE_ITEF is not set
+# CONFIG_NSH_DISABLE_LOOPS is not set
+# CONFIG_NSH_DISABLE_LOSETUP is not set
+# CONFIG_NSH_DISABLE_MKRD is not set
+# CONFIG_NSH_DISABLE_PS is not set
+# CONFIG_NSH_DISABLE_PUT is not set
+# CONFIG_NSH_DISABLE_SEMICOLON is not set
+# CONFIG_NSH_DISABLE_UNAME is not set
+# CONFIG_NSH_DISABLE_WGET is not set
+# CONFIG_NSH_DISABLE_XD is not set
+CONFIG_ARCH="arm"
+CONFIG_ARCH_BOARD="xiao-seeeduino"
+CONFIG_ARCH_BOARD_XIAO_SEEEDUINO=y
+CONFIG_ARCH_CHIP="samd2l2"
+CONFIG_ARCH_CHIP_SAMD21J18A=y
+CONFIG_ARCH_CHIP_SAMD2X=y
+CONFIG_ARCH_STACKDUMP=y
+CONFIG_BOARD_LOOPSPERMSEC=3410
+CONFIG_BUILTIN=y
+CONFIG_DEFAULT_SMALL=y
+CONFIG_EXAMPLES_HELLO=y
+CONFIG_HAVE_CXX=y
+CONFIG_HAVE_CXXINITIALIZE=y
+CONFIG_INIT_ENTRYPOINT="nsh_main"
+CONFIG_INIT_STACKSIZE=1536
+CONFIG_INTELHEX_BINARY=y
+CONFIG_NSH_BUILTIN_APPS=y
+CONFIG_POSIX_SPAWN_DEFAULT_STACKSIZE=1536
+CONFIG_PTHREAD_STACK_DEFAULT=1536
+CONFIG_RAM_SIZE=32768
+CONFIG_RAM_START=0x20000000
+CONFIG_RR_INTERVAL=200
+CONFIG_SAMD2L2_SERCOM4=y
+CONFIG_SCHED_WAITPID=y
+CONFIG_START_DAY=18
+CONFIG_START_MONTH=10
+CONFIG_START_YEAR=2024
+CONFIG_SYSTEM_NSH=y
+CONFIG_TASK_NAME_SIZE=0
+CONFIG_USART4_RXBUFSIZE=64
+CONFIG_USART4_SERIAL_CONSOLE=y
+CONFIG_USART4_TXBUFSIZE=64