RaspberryPi rp2040

Tags: chip:rp2040

The RP2040 is a dual core chip produced by the RaspberryPi Foundation that is based on ARM Cortex-M0+.

Peripheral Support

The following list indicates RP2040 peripherals currently supported in NuttX:

Peripheral	Notes
GPIO	See Supported Boards documentation for available pins.
UART	GPIO 0 (UART0 TX) and GPIO 1 (UART0 RX) are often used for the console.
I2C
SPI
DMAC
PWM
USB
PIO	RP2040 Programmable I/O
IRQs
DMA
Clock Output
ws2812	Smart pixels (e.g. Neopixel)
Flash ROM Boot
SRAM Boot	If Pico SDK is available a nuttx.uf2 file will be created
BMP180	Requires I2C0
INA219	Requires I2C0

The Pico Display Pack (ST7789 LCD) and Pico Audio Pack (PCM5100A I2S DAC) are also available.

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

SPI Slave Mode
SSI
RTC
Timers

Additionally, some supported features are:

Persistent flash filesystem in unused flash ROM
WiFi wireless communication (for capable boards such as the Pico W)

Installation

Download the Raspberry Pi Pico SDK:

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

Download and install the picotool

Instructions for installing/building it can be found here: https://github.com/raspberrypi/picotool

If you are on Arch Linux, you can also install the picotool through the AUR:
```
$ yay -S picotool
```
Set PICO_SDK_PATH environment variable to point to the cloned SDK:
```
$ export PICO_SDK_PATH=<absolute_path_to_pico-sdk_directory>
```
You will have to do this every time you restart the terminal where you are building NuttX, so it might be best to include this command in your bashrc so NuttX’s build system always knows where to find the SDK.

Download NuttX and NuttX applications. These must both be contained in the same directory:

$ git clone https://github.com/apache/nuttx.git nuttx
$ git clone https://github.com/apache/nuttx-apps.git apps

Now you have all of the required dependencies for building NuttX for the RP2040.

Building NuttX

Change to the NuttX directory:
```
$ cd nuttx
```
Select a configuration. The available configurations can be listed with the command:
```
$ ./tools/configure.sh -L
```
The one you choose will be dependent on the board you want to build for, like raspberrypi-pico:usbnsh to use the usbnsh configuration for the Raspberry Pi Pico.

Load the selected configuration:

$ make distclean
$ ./tools/configure.sh <selected_configuration>

Modify the configuration as needed (optional):
```
$ make menuconfig
```
Build NuttX:
```
$ make
```

The output of the build process will be a file called nuttx.uf2, which you are able to flash to the RP2040.

Programming

Programming using BOOTSEL

Connect the board to the USB port of your host computer while pressing down the BOOTSEL button.

Note

Some boards call it a different name, and some boards use pins that need to be jumpered instead of buttons. Consult the documentation for your particular board.

Note

If your board comes with a BOOTSEL and a RESET button, you might find it easier to hold down the BOOTSEL button and then press RESET, all while the board is still plugged in via USB. This will trigger the boot mode without having to constantly unplug and plug in the USB cable.

The board should be detected as USB Mass Storage Device, which you can mount in your file explorer just like a USB drive.

Then copy nuttx.uf2 onto the device. It should reboot itself into NuttX once the UF2 file is done copying over!

Programming using SDB

Most (but not all) RP2040 boards provide a serial (SDB) debug port. The “nuttx” ELF file can be uploaded with an appropriate SDB programmer module and companion software.

Running NuttX

The usbnsh configuration that most supported boards provide allows console access by USB CDC/ACM serial device. The console is available by using a terminal software on your host computer with the device plugged in. Some options are:

PuTTY
Minicom
Picocom

Many configurations may also provide access to the console via UART0. To access this console from your host computer, GPIO 0 and 1 pins on your board must be connected to a USB-serial converter (and typically the GND pin as well), which is plugged into your computer. You can then use your terminal software just like with usbnsh.

Note

Most configurations will run the console at 115200 baud.

Supported Boards

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.