walnux/Documentation/platforms/arm/rp2040/boards/adafruit-qt-py-rp2040/index.rst

=======================
Adafruit QT Py RP2040
=======================

.. tags:: chip:rp2040

The QT Py RP2040 is a tiny general purpose RP2040 board supplied by 
Adafruit.

.. figure:: QT-Py.png
   :align: center

See the `Adafruit website <https://learn.adafruit.com/adafruit-qt-py-2040/>`_
for information about the Adafruit QT Py RP2040.

Features
========

* RP2040 microcontroller chip
* Dual-core ARM Cortex M0+ processor, flexible clock running up to 133 MHz
* 264kB of SRAM, and 8MB of on-board Flash memory
* Castellated module allows soldering direct to carrier boards
* USB Host and Device support via type C connector.
* Low-power sleep and dormant modes
* Drag & drop programming using mass storage over USB
* 13 multi-function GPIO pins (11 breakout pads and two QT pads)
* 2× SPI, 2× I2C, 2× UART, 4× 12-bit ADC, 16× controllable PWM channels
* Accurate clock and timer on-chip
* Temperature sensor
* Accelerated floating point libraries on-chip
* 8 × Programmable IO (PIO) state machines for custom peripheral support

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

By default a serial console appears on GPIO pins 20 (RX GPIO1) and pin 5
(TX GPIO1).  This console runs a 115200-8N1.

The board can be configured to use the USB connection as the serial console.

Buttons and LEDs
================

A ws2812 (NeoPixel) smart RGB LED controlled by GPIO12 (data) and
GPIO11 (power).

There is a BOOT button which if held down when power is first
applied or the RESET button is pressed will cause the RP2040 to
boot into program mode and appear as a storage device to
a USB connecter.  Saving a .UF2 file to this device will 
replace the Flash ROM contents on the RP2040.

A RESET button that allows rebooting the board without disconnecting
the power.

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

===== ========== ==========
Pad   Signal     Notes
===== ========== ==========
1     GPIO26     ADC0
2     GPIO27     ADC1
3     GPIO28     ADC2
4     GPIO29     ADC3
5     GPIO24
6     GPIO25
7     GPIO20     Default TX for UART1 serial console
8     GPIO5      Default RX for UART1 serial console
9     GPIO6      
10    GPIO4
11    GPIO3
12    3.3V       Power out to peripherals.
13    Ground
14    5V
===== ========== ==========

The board has a STEMMA QT connector that is also connected to
pins GPIO22 (I2C1 SDA) and GPIO23 (I2C1 SCL).

Power Supply 
============

The Raspberry Pi Pico can be powered via the USB connector,
or by supplying +5V to pin 14.  The board had a diode that prevents
power from pin 14 from flowing back to the USB socket, although
this can be disabled by connecting on-board solder pads if there
is need to run as a usb host.

The Raspberry Pi Pico chip run on 3.3 volts which is supplied by
an on board regulator.

Supported Capabilities
======================

NuttX supports the following RP2040 capabilities:

* UART  (console port)

  * GPIO 0 (UART0 TX) and GPIO 1 (UART0 RX) are used for the console.

* I2C
* SPI (master only)
* DMAC
* PWM
* ADC
* Watchdog
* USB device

  * MSC, CDC/ACM serial and these composite device are supported.
  * CDC/ACM serial device can be used for the console.

* PIO (RP2040 Programmable I/O)
* Flash ROM Boot
* SRAM Boot

  * If Pico SDK is available, nuttx.uf2 file which can be used in BOOTSEL mode will be created.

* Persistent flash filesystem in unused flash ROM
* WiFi wireless communication

There is currently no direct user mode access to these RP2040 hardware features:

* SPI Slave Mode
* SSI
* RTC
* Timers

NuttX also provide support for these external devices:

* WS2812 smart pixel support

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 adafruit-qt-py-rp2040:nsh
  $ make V=1

5. Connect the Adafruit QT Py RP2040 board to USB port while pressing BOOT.
   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 20 (TX) and GPIO 5 (RX) pins must be connected to
   the device such as USB-serial converter.

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

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

gpio
--------

NuttShell configuration (console enabled in UART1, at 115200 bps) with GPIO examples.

nsh
---

Basic NuttShell configuration (console enabled in UART1, at 115200 bps).

nsh-flash
---------

Basic NuttShell configuration (console enabled in UART0, at 115200 bps
with SMART flash filesystem.

nshsram
-------

NuttShell configuration (console enabled in UART1, at 115200 bps) with interrupt
vectors in RAM.

smp
---

Basic NuttShell configuration (console enabled in UART1, at 115200 bps) with
both ARM cores enabled.

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.