Raspberry Pi Pico

The Raspberry Pi Pico is a general purpose board supplied by the Raspberry Pi Foundation.

../../../../../_images/RaspberryPiPico.png

Features

  • RP2040 microcontroller chip

  • Dual-core ARM Cortex M0+ processor, flexible clock running up to 133 MHz

  • 264kB of SRAM, and 2MB of on-board Flash memory

  • Castellated module allows soldering direct to carrier boards

  • USB 1.1 Host and Device support

  • Low-power sleep and dormant modes

  • Drag & drop programming using mass storage over USB

  • 26 multi-function GPIO pins

  • 2× SPI, 2× I2C, 2× UART, 3× 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 pins 1 (TX GPIO0) and pin 2 (RX GPIO1). This console runs a 115200-8N1.

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

Buttons and LEDs

User LED controlled by GPIO25.

A BOOTSEL 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

1

GPIO0

Default TX for UART0 serial console

2

GPIO1

Default RX for UART0 serial console

3

Ground

4

GPIO2

5

GPIO3

6

GPIO4

Default SDA for I2C0

7

GPIO5

Default SCL for I2C0

8

Ground

9

GPIO6

Default SDA for I2C1

10

GPIO7

Default SCL for I2C1

11

GPIO8

Default RX for SPI1

12

GPIO9

Default CSn for SPI1

13

Ground

14

GPIO10

Default SCK for SPI1

15

GPIO11

Default TX for SPI1

16

GPIO12

17

GPIO13

18

Ground

19

GPIO14

20

GPIO15

21

GPIO16

Default RX for SPI0

22

GPIO17

Default CSn for SPI0

23

Ground

24

GPIO18

Default SCK for SPI0

25

GPIO19

Default TX for SPI0

26

GPIO20

Default TX for UART1 serial console

27

GPIO21

Default RX for UART1 serial console

28

Ground

29

GPIO22

30

Run

31

GPIO26

ADC0

32

GPIO27

ADC1

33

AGND

Analog Ground

34

GPIO28

ADC2

35

ADC_VREF

Analog reference voltage

36

3V3

Power output to peripherals

37

3V3_EN

Pull to ground to turn off.

38

Ground

39

VSYS

+5V Supply to board

40

VBUS

Connected to USB +5V

Other RP2040 Pins

GPIO23 Output - Power supply control. GPIO24 Input - High if USB port or Pad 40 supplying power. GPIO25 Output - On board LED. ADC3 Input - Analog voltage equal to one third of VSys voltage.

Separate pins for the Serial Debug Port (SDB) are available

Power Supply

The Raspberry Pi Pico can be powered via the USB connector, or by supplying +5V to pin 39. The board had a diode that prevents power from pin 39 from flowing back to the USB socket, although the socket can be power via pin 30.

The Raspberry Pi Pico chip run on 3.3 volts. This is supplied by an onboard voltage regulator. This regulator can be disabled by pulling pin 37 to ground.

The regulator can run in two modes. By default the regulator runs in PFM mode which provides the best efficiency, but may be switched to PWM mode for improved ripple by outputting a one on GPIO23.

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:

  • 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)

  • SHT4X sensor at I2C0

  • 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

Installation

  1. Download Raspberry Pi Pico SDK

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

  1. 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:

$ yay -S picotool

  1. Set PICO_SDK_PATH environment variable

$ export PICO_SDK_PATH=<absolute_path_to_pico-sdk_directory>

  1. 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

  1. 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.)

  2. 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

audiopack

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for NXPlayer audio player.

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

bmp280

NuttShell configuration (console enabled in USB Port, at 115200 bps) with support for Bosch BMP280 sensor:

nsh> bmp280
Absolute pressure [hPa] = 1008.460022
Temperature [C] = 21.809999
nsh>

composite

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for CDC/ACM with MSC USB composite driver. conn command enables the composite device.

displaypack

NuttShell configuration (console enabled in USB Port, at 115200 bps) supporting ST7789 video display.

See the following page for connection: https://shop.pimoroni.com/products/pico-display-pack

enc28j60

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for ENC28J60.

ENC28J60 SPI ethernet controller supports:

  • IP address is configured by DHCP.

  • DNS address is 8.8.8.8 (CONFIG_NETINIT_DNSIPADDR)

  • NTP client is enabled.

ENC28J60 connections

ENC28J60

Raspberry Pi Pico

GND

GND (Pin 3 or 38 or …)

3.3V

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)

lcd1602

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for LCD1602 Segment LCD Display (I2C).

LCD1602 connections

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)

nsh

Basic NuttShell configuration (console enabled in UART0, 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 UART0, at 115200 bps) with interrupt vectors in RAM.

smp

Basic NuttShell configuration (console enabled in UART0, at 115200 bps) with both ARM cores enabled.

spisd

NuttShell configuration (console enabled in UART0, at 115200 bps) with SPI SD card support enabled.

spisd connections

SD card slot

Raspberry Pi Pico

DAT2

Not connected

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

Not connected

Card hot swapping is not supported.

ssd1306

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for SSD1306 OLED display (I2C) test configuration.

SSD1306 connections

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)

st7735

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for ST7735 SPI LCD.

ST7735 connections

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)

usbmsc

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for USB MSC and CDC/ACM.

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.

usbnsh

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

waveshare-lcd-1.14

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for st7789.

waveshare-lcd-1.3

NuttShell configuration (console enabled in UART0, at 115200 bps) with support for usbmsc.

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.