========================
Seeed Studio Xiao RP2040
========================

The `Seeed Studio Xiao RP2040 <https://wiki.seeedstudio.com/XIAO-RP2040/>`_ is a general purpose board supplied by
Seeed Studio and it is compatible with the Raspberry Pi RP2040 ecosystem as they share the same RP2040 chip.

.. figure:: seeed-xiao-rp2040.jpg
   :align: center

Features
========

* RP2040 microcontroller chip
* Dual-core ARM Cortex M0+ processor, flexible clock running up to 133 MHz
* 264KB of SRAM, and 2MB of onboard Flash memory
* 11 digital pins, 4 analog pins, 11 PWM Pins
* 1 I2C interface, 1 UART interface, 1 SPI interface, 1 SWD Bonding pad interface
* USB Type-C interface
* 1 user LED, 1 power LED, two LEDs for serial port downloading, 1 RGB LED
* 1 RESET button, 1 BOOT button

Serial Console
==============

By default a serial console appears on pins 6 (TX GPIO0) and pin 7
(RX GPIO1).  This console runs a 115200-8N1.
The board can be configured to use the USB connection as the serial console.

LEDs
====

There are 2 LEDs available for user:

- A RGB LED connected to GPIO16 (PIN_LED_G), GPIO17 (PIN_LED_R), GPIO25 (PIN_LED_B).
- A NeoPixel RGB LED connected to GPIO11 (NEOPIXEL_POWER) and GPIO12 (PIN_NEOPIXEL).

Buttons
=======

There are 2 buttons available:

A RESET button and a BOOT button, which if held down when power is first
applied to the board, will cause the RP2040 to boot into programming
mode and appear as a storage device to a computer connected via USB.
Saving a .UF2 file to this device will replace the Flash ROM contents
on the RP2040.


Pin Mapping
===========
Pads numbered anticlockwise from USB connector.

===== ========== ==========
Pad   Signal     Notes
===== ========== ==========
0     GPI26      D0/A0
1     GPI27      D1/A1
2     GPI28      D2/A2
3     GPI29      D3/A3
4     GPIO6      D4/SDA
5     GPIO7      D5/SCL
6     GPIO0      Default TX for UART0 serial console
7     GPIO1      Default RX for UART1 serial console/CSn
8     GPIO2      D8/SCK
9     GPIO3      D10/MOSI
10    GPIO4      D9/MicroSD
11    3V3        Power output to peripherals
12    Ground
13    VIN        +5V Supply to board
===== ========== ==========

Power Supply
============
For general I/O pins:

Working voltage of MCU is 3.3V. Voltage input connected to general I/O pins
may cause chip damage if it' higher than 3.3V.

For power supply pins:

The built-in DC-DC converter circuit able to change 5V voltage into 3.3V allows
to power the device with a 5V supply via VIN-PIN and via the USB connector.

Installation
============

1. Download Raspberry Pi Pico SDK.

.. code-block:: console

  $ git clone -b 2.0.0 https://github.com/raspberrypi/pico-sdk.git

2. Download and install picotool

  Instructions can be found here: https://github.com/raspberrypi/picotool

  If you are on Arch Linux, you can install the picotool through the AUR:

.. code-block:: console

  $ yay -S picotool

3. Set PICO_SDK_PATH environment variable

.. code-block:: console

  $ export PICO_SDK_PATH=<absolute_path_to_pico-sdk_directory>

4. Configure and build NuttX

.. code-block:: console

  $ git clone https://github.com/apache/nuttx.git nuttx
  $ git clone https://github.com/apache/nuttx-apps.git apps
  $ cd nuttx
  $ make distclean
  $ ./tools/configure.sh seeed-xiao-rp2040:nsh
  $ make V=1

5. Connect the Seeed Studio Xiao RP2040 board to USB port while pressing BOOTSEL
   (small button marked "B"). The board will be detected as USB Mass Storage
   Device. Then copy "nuttx.uf2" into the device. (Same manner as the standard
   Pico SDK applications installation)

6. To access the console, GPIO 0 and 1 pins must be connected to the
   device such as USB-serial converter.

   `usbnsh` configuration provides the console access by USB CDC/ACM serial
   device.  The console is available by using a terminal software on the USB
   host.

Configurations
==============

nsh
---

Basic NuttShell configuration (console enabled in UART0, at 115200 bps).

userled
-------

This is an nsh configuration with added support for user LEDs.

usbnsh
------

Basic NuttShell configuration using CDC/ACM serial (console enabled in USB Port,
at 115200 bps).

License exceptions
==================

The following files are originated from the files in Pico SDK.
So, the files are licensed under 3-Clause BSD same as Pico SDK.

* arch/arm/src/rp2040/rp2040_clock.c
* arch/arm/src/rp2040/rp2040_pll.c
* arch/arm/src/rp2040/rp2040_xosc.c

  * These are created by referring the Pico SDK clock initialization.

* arch/arm/src/rp2040/rp2040_pio.c
* arch/arm/src/rp2040/rp2040_pio.h
* arch/arm/src/rp2040/rp2040_pio_instructions.h

  * These provide the similar APIs to Pico SDK's hardware_pio APIs.

* arch/arm/src/rp2040/hardware/\*.h

  * These are generated from rp2040.svd originally provided in Pico SDK.