README
======

This directory contains the port of NuttX to the Raspberry Pi Pico.
See https://www.raspberrypi.org/products/raspberry-pi-pico/ for information
about Raspberry Pi Pico.

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

NuttX also provide support for these external devices:

  - BMP180 sensor at I2C0 (don't forget to define I2C0 GPIOs at "I2C0 GPIO pin assign" in Board Selection menu)
  - INA219 sensor / module (don't forget to define I2C0 GPIOs at "I2C0 GPIO pin assign" in Board Selection menu)
  - Pico Display Pack (ST7789 LCD)
    - RGB leds and buttons are not supported yet.
  - Pico Audio Pack (PCM5100A I2S DAC)
    - I2S interface is realized by PIO.
  - WS2812 smart pixel support

There is currently no direct user mode access to these RP2040 hardware features:
  - SPI Slave Mode
  - SSI
  - RTC
  - Timers

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

1. Download Raspberry Pi Pico SDK

  $ git clone -b 1.1.2 https://github.com/raspberrypi/pico-sdk.git

2. Set PICO_SDK_PATH environment variable

  $ export PICO_SDK_PATH=<absolute_path_to_pico-sdk_directory>

3. Configure and build NuttX

  $ 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 raspberrypi-pico:nsh
  $ make V=1

4. Connect Raspberry Pi Pico board to USB port while pressing BOOTSEL.
   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.)

5. 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
   devcice.  The console is available by using a terminal software on the USB
   host.

Defconfigs
==========

- nsh
    Minimum configuration with NuttShell

- nsh-flash
    NuttX shell with SMART flash filesystem.

- nshsram
    Load NuttX binary to SRAM
  
- smp
    Enable SMP mode. Both Core 0 and Core 1 are used by NuttX.

- ssd1306
    SSD1306 OLED display (I2C) test configuration
    Connection:
       SSD1306       Raspberry Pi Pico
           GND ----- GND            (Pin 3 or 38 or ...)
           VCC ----- 3V3 OUT        (Pin 36)
           SDA ----- GP4 (I2C0 SDA) (Pin 6)
           SCL ----- GP5 (I2C0 SCL) (Pin 7)
           
- lcd1602 
    LCD 1602 Segment LCD Disaply (I2C)
    Connection:
    PCF8574 BackPack Raspberry Pi Pico
           GND ----- GND            (Pin 3 or 38 or ...)
           VCC ----- 5V Vbus        (Pin 40)
           SDA ----- GP4 (I2C0 SDA) (Pin 6)
           SCL ----- GP5 (I2C0 SCL) (Pin 7)
- spisd
    SD card support (SPI connection)
    Connection:
      SD card slot   Raspberry Pi Pico
       DAT2          (NC)
       DAT3/CS ----- GP17 (SPI0 CSn) (Pin 22)
       CMD /DI ----- GP19 (SPI0 TX)  (Pin 25)
       VDD     ----- 3V3 OUT         (Pin 36)
       CLK/SCK ----- GP18 (SPI0 SCK) (Pin 24)
       VSS     ----- GND             (Pin 3 or 38 or ...)
       DAT0/DO ----- GP16 (SPI0 RX)  (Pin 21)
       DAT1          (NC)
    * Card hot swapping is not supported.

- st7735
    st7735 SPI LCD support      
    Connection:
      st7735         Raspberry Pi Pico
           GND ----- GND             (Pin 3 or 38 or ...)
           VCC ----- 5V Vbus         (Pin 40)
           SDA ----- GP15 (SPI1 TX)  (Pin 20)
           SCK ----- GP14 (SPI1 SCK) (Pin 19)
            CS ----- GP13 (SPI1 CSn) (Pin 17)
       AO(D/C) ----- GP12 (SPI1 RX)  (Pin 16)
            BL ----- GP11            (Pin 15)
         RESET ----- GP10            (Pin 14)  

- enc28j60
    ENC28J60 SPI ethernet controller support
      - IP address is configured by DHCP.
      - DNS address is 8.8.8.8 (CONFIG_NETINIT_DNSIPADDR)
      - NTP client is enabled.
    Connection:
      ENC28J60       Raspberry Pi Pico
           GND ----- GND             (Pin 3 or 38 or ...)
           3.3 ----- 3V3 OUT         (Pin 36)
            SI ----- GP15 (SPI1 TX)  (Pin 20)
           SCK ----- GP14 (SPI1 SCK) (Pin 19)
            CS ----- GP13 (SPI1 CSn) (Pin 17)
            SO ----- GP12 (SPI1 RX)  (Pin 16)
           INT ----- GP11            (Pin 15)
         RESET ----- GP10            (Pin 14)

- displaypack
    Pico Display Pack support
    See the following page for connection:
      https://shop.pimoroni.com/products/pico-display-pack

- audiopack
    Pico Audio Pack support
    See the following page for connection:
      https://shop.pimoroni.com/products/pico-audio-pack
    SD card interface is also enabled.

- usbnsh
    USB CDC/ACM serial console with NuttShell

- usbmsc
    USB MSC and CDC/ACM support
    `msconn` and `sercon` commands enable the MSC and CDC/ACM devices.
    The MSC support provides the interface to the SD card with SPI,
    so the SD card slot connection like spisd configuration is required.

- composite
    USB composite device (MSC + CDC/ACM) support
    `conn` command enables the composite device.

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.
