Waveshare RP2040-Zero

The RP2040 SoC [31] by Raspberry Pi Ltd. is a small sized and low-cost 32-bit dual ARM Cortex-M0+ microcontroller and predestined for versatile board designs. The Waveshare RP2040 board series based on this microcontroller offers a wide range with different scaling factors, in size, features and interfaces for communication, input and output.

Board Overview

Hardware

The RP2040-Zero [17] is a mini sized RP2040 development board. The on-board USB-C connector makes it compatible to future standards. The castellated module allows soldering direct to carrier boards.

Features and Resources

Printed Circuit Board

5V/480㎃ 3.3V/800㎃ 3.3V(OUT) 133㎒ 2㎆ 264㎅ RST RGB USB-C UF2 20+9 16 4 2 1 1 Dual core Arm Cortex-M0+ processor running up to 133㎒ 264㎅ on-chip SRAM 2㎆ on-board QSPI flash with XIP capabilities USB 1.1 controller (host/device) On-board USB-C connector On-board 3.3V LDO regulator with 800㎃ On-board RESET button On-board BOOT button On-board RGB LED 20 GPIO pins via edge pinout 9 GPIO pins via solder points 1 UART peripherals via edge pinout 2 I2C controllers via edge pinout 1 SPI controllers via edge pinout 4 PWM channels via edge pinout 9 PWM channels via solder points 4 ADC analog inputs via edge pinout 8 Programmable I/O (PIO) state machines for custom peripherals 1 Watchdog timer peripheral 1 Temperature sensor on-chip Design Data RP2040-Zero Schematic [18] RP2040-Zero STEP 3D-Model [18] RP2040-Zero WS2812 Test [19] in C/Pico-SDK and Python/Thonny IDE

Positions

USB Type-C connector Supports USB1.1 hosts and slave devices W25Q16JV 2㎆ NOR-Flash BOOT button press it when resetting to enter download mode RESET button WS2812B RGB LED ME6217C33 800㎃ low dropout, low noise, ultra-fast LDO RP2040 RP2040 pins 10 solder points, including 9 GPIO pins

Data Sheets

• RP2040 SoC [31]

• RP2040 Datasheet [32]

• Hardware design with RP2040 [33]

• W25Q16JV [29]

• W25Q16JV Datasheet [30]

• WS2812B [21]

• WS2812B Datasheet V5 [22]

• WS2812B Datasheet V2 [23]

• WS2812B Datasheet V1 [24]

• Understanding the WS2812 [25]

• WS2812B with RP2040 PIO & DMA [26]

• ME6217C33 [27]

• ME6217 Datasheet [28]

Flash partitions

QSPI NOR-Flash	bootrom	code_partition	storage_partition
primary 2㎆	256B	1㎆ - 256B	1㎆

Pinouts

The peripherals of the RP2040 SoC [31] can be routed to various pins on the board. The configuration of these routes can be modified through DTS. Please refer to the datasheet to see the possible routings for each peripheral. The default assignments for the board is defined below.

External pin mapping on the RP2040-Zero is not identical to the original Raspberry Pi Pico board. Almost all pins are rearranged in a more compact order. Likewise, the voltage sense and monitoring functions are not integrated. Thus all internal R2040 GPIO lines are available for free use, insofar there is sufficient space for them on the outer edge of the board or on the bottom side by additional solder points.

Only GPIO line 16 is exclusively routed to the on-board user RGB LED. The analog voltage reference is internally hard-wired to the digital 3.3V power supply and only decoupled by a simple resistor. There is no option to change this from outside the board.

Pin Mapping

Pinout

on-edge(1-23): 6 4 4 2 1 1 on-pads(A-J): 9 9 on-board: 1 RGB Default Zephyr Peripheral Mapping   1 UART0_TX : GP0 (PWM0) 2 UART0_RX : GP1 (PWM1) 3 (UART0_CTS) : GP2 (PWM2) 4 (UART0_RTS) : GP3 (PWM3) 5 SPI0_RX : GP4 (PWM4) 6 SPI0_CSN : GP5 (PWM5) 7 SPI0_SCK : GP6 (PWM6) 8 SPI0_TX : GP7 (PWM7) 9 I2C0_SDA : GP8 (PWM8) 10 I2C0_SCL : GP9 (PWM9) 11 PIO/PWM : GP10 PWM10 12 PIO/PWM : GP11 PWM11 13 PIO/PWM : GP12 PWM12 14 PIO/PWM : GP13 PWM13 15 I2C1_SDA : GP14 (PWM14) 16 I2C1_SCL : GP15 (PWM15) nc PIO0 : GP16 (PWM0) nc on-board user RGB_LED_DI A PIO/PWM : GP17 PWM1 B PIO/PWM : GP18 PWM2 C PIO/PWM : GP19 PWM3 D PIO/PWM : GP20 PWM4 E PIO/PWM : GP21 PWM5 F PIO/PWM : GP22 PWM6 G PIO/PWM : GP23 PWM7 H PIO/PWM : GP24 PWM8 I PIO/PWM : GP25 PWM9 J GND 17 ADC_CH0 : GP26 (PWM10) 18 ADC_CH1 : GP27 (PWM11) 19 ADC_CH2 : GP28 (PWM12) 20 ADC_CH3 : GP29 (PWM13) 21 3V3(OUT) 22 GND 23 VSYS Devicetree compatible waveshare,rp2040mini-header waveshare,rp2040mini-pcbpads worldsemi,ws2812-rpi_pico-pio

Supported Features

Similar to the Raspberry Pi Pico the board configuration supports the following hardware features:

Hardware Features Supported by Zephyr

Peripheral	Kconfig option	Devicetree compatible	Zephyr API
PINCTRL	CONFIG_PINCTRL	raspberrypi,pico-pinctrl	Pin Control API
GPIO	CONFIG_GPIO	raspberrypi,pico-gpio	General-Purpose Input/Output (GPIO)
UART	CONFIG_SERIAL	raspberrypi,pico-uart arm,pl011	Universal Asynchronous Receiver-Transmitter (UART)
UDC (USB Device Controller)	CONFIG_USB_DEVICE_STACK_NEXT	raspberrypi,pico-usbd	USB device support APIs
I2C	CONFIG_I2C	raspberrypi,pico-i2c	Inter-Integrated Circuit (I2C) Bus
SPI	CONFIG_SPI	raspberrypi,pico-spi arm,pl022	Serial Peripheral Interface (SPI) Bus
PWM	CONFIG_PWM	raspberrypi,pico-pwm	Pulse Width Modulation (PWM)
ADC	CONFIG_ADC	raspberrypi,pico-adc	Analog-to-Digital Converter (ADC)
Temperature (Sensor)	CONFIG_SENSOR	raspberrypi,pico-temp	Sensors
RTC	CONFIG_RTC	raspberrypi,pico-rtc	Real-Time Clock (RTC)
Timer (Counter)	CONFIG_COUNTER	raspberrypi,pico-timer	Counter
Watchdog Timer (WDT)	CONFIG_WATCHDOG	raspberrypi,pico-watchdog	Watchdog
Flash	CONFIG_FLASH	raspberrypi,pico-flash-controller	Flash and Flash map
PIO	CONFIG_PIO_RPI_PICO	raspberrypi,pico-pio	N/A
UART (PIO)	CONFIG_SERIAL	raspberrypi,pico-uart-pio	Universal Asynchronous Receiver-Transmitter (UART)
SPI (PIO)	CONFIG_SPI	raspberrypi,pico-spi-pio	Serial Peripheral Interface (SPI) Bus
DMA	CONFIG_DMA	raspberrypi,pico-dma	Direct Memory Access (DMA)
HWINFO	CONFIG_HWINFO	N/A	Hardware Information
VREG	CONFIG_REGULATOR	raspberrypi,core-supply-regulator	Regulators
RESET	CONFIG_RESET	raspberrypi,pico-reset	Reset Controller
CLOCK	CONFIG_CLOCK_CONTROL	raspberrypi,pico-clock-controller raspberrypi,pico-clock	Clock Control
NVIC	N/A	arm,v6m-nvic	Nested Vector Interrupts Controller
SYSTICK	N/A	arm,armv6m-systick

Other hardware features are not currently supported by Zephyr. The default configuration can be found in the different Kconfig files:

• boards/waveshare/rp2040_zero/waveshare_rp2040_zero_defconfig

Board Configurations

The board can be configured for the following different use cases.

west build -b waveshare_rp2040_zero

Use the serial port UART0 on edge header as Zephyr console and for the shell.

west build -b waveshare_rp2040_zero -S usb-console

Use the native USB device port with CDC-ACM as Zephyr console and for the shell.

Connections and IOs

The Waveshare wiki [16] has detailed information about board connections. Download the different schematics or datasheets as linked above per board for more details. The pinout diagrams can also be found there.

System Clock

The RP2040 [31] MCU is configured to use the 12㎒ external crystal with the on-chip PLL generating the 125㎒ system clock. The internal AHB and APB units are set up in the same way as the upstream Raspberry Pi Pico C/C++ SDK [11] libraries.

GPIO (PWM) Ports

The RP2040 [31] MCU has 1 GPIO cell which covers all I/O pads and 8 PWM function unit each with 2 channels beside a dedicated Timer unit. Only 13 PWM channels are available on the edge connectors, but not supported in default configuration. There is also no internal on-board component that requires or use any PWM functionality.

ADC/TS Ports

The RP2040 [31] MCU has 1 ADC with 4 channels and an additional fifth channel for the on-chip temperature sensor (TS). The ADC channels 0-3 are available on the Waveshare RP2040 Mini header.

The external voltage reference ADC_VREF is directly connected to the 3.3V power supply.

SPI Port

The RP2040 [31] MCU has 2 SPIs. To the edge connectors SPI0 is usable for external devices over GP7 (MOSI), GP4 (MISO), GP6 (SCK), and GP5 (CSn) on the Waveshare RP2040 Mini header. SPI1 is not available in any default setup.

I2C Port

The RP2040 [31] MCU has 2 I2Cs. The default serial bus I2C0 is usable for external devices over GP8 (I2C0_SDA) and GP9 (I2C0_SCL). I2C1 is not available in any default setup, but could be configured to GP14 (I2C1_SDA) and GP15 (I2C1_SCL) on the Waveshare RP2040 Mini header.

Serial Port

The RP2040 [31] MCU has 2 UARTs. One of the UARTs (UART0) is connected to external devices over GP0 (TX) and GP1 (RX) on the Waveshare RP2040 Mini header, optional with full featured EIA 232D handshake signals, and is the Zephyr console. UART1 is not available in any default setup.

USB Device Port

The RP2040 [31] MCU has a (native) USB device port that can be used to communicate with a host PC. See the USB sample applications for more, such as the USB CDC ACM UART sample sample which sets up a virtual serial port that echos characters back to the host PC. As an alternative to the default Zephyr console on serial port the Bridle USB Console Snippet (usb-console) can be used to enable CDC ACM and switch the console to USB:

USB device idVendor=2e8a, idProduct=000a, bcdDevice= 4.04
USB device strings: Mfr=1, Product=2, SerialNumber=3
Product: RP2040-Zero (CDC ACM)
Manufacturer: Waveshare (Raspberry Pi)
SerialNumber: B69F8448A6E91514

To integrate specific USB device functions that do not follow a USB standard class, the following alternate identifier numbers are available for the various Waveshare RP2040 and RP2350 boards according to the Raspberry Pi USB product ID list [10]:

RP2040

0x101F:

RP2040-Zero

0x1020:

RP2040-Plus

0x1021:

RP2040-LCD-0.96

0x1039:

RP2040-LCD-1.28

0x103A:

RP2040-One

0x1044:

Power Management HAT (B)

0x1055:

RP2040-ETH

0x1056:

RP2040-Geek

0x1057:

RP2040-Touch-LCD-1.28

0x1083:

RP2040-PiZero

0x1084:

RP2040-Tiny

0x1085:

RP2040-Matrix

0x1086:

RP2040-BLE

0x1087:

PICO-Cam-A

RP2350

0x10B0:

RP2350-Zero

0x10B1:

RP2350-Plus

0x10B2:

RP2350-Tiny

0x10B3:

RP2350-LCD-1.28

0x10B4:

RP2350-Touch-LCD-1.28

0x10B5:

RP2350-One

0x10B6:

RP2350-Geek

0x10B7:

RP2350-LCD-0.96

0x10C3:

RP2350-ETH

 

Programmable I/O (PIO)

The RP2040 SoC [31] comes with two PIO periherals. These are two simple co-processors that are designed for I/O operations. The PIOs run a custom instruction set, generated from a custom assembly language. PIO programs are assembled using pioasm, a tool provided by Raspberry Pi. Further information can be found in the Raspberry Pi Pico C/C++ SDK [11] document, section with title “Using PIOASM, the PIO Assembler”.

Zephyr does not (currently) assemble PIO programs. Rather, they should be manually assembled and embedded in source code. An example of how this is done can be found at drivers/serial/uart_rpi_pico_pio.c or drivers/spi/spi_rpi_pico_pio.c.

Programming and Debugging

Flashing

The board can only be flashed with a UF2 file. There is no SWD connector.

Using UF2

By default, building an application for the board will generate a build/zephyr/zephyr.uf2 file. If the board is powered on with the BOOTSEL button pressed, it will appear on the host as a mass storage device:

USB device idVendor=2e8a, idProduct=0003, bcdDevice= 1.00
USB device strings: Mfr=1, Product=2, SerialNumber=0
Product: RP2 Boot
Manufacturer: Raspberry Pi
SerialNumber: E0C9125B0D9B

The UF2 file should be drag-and-dropped or copied on command line to the device, which will then flash the board.

RP2040 Boot-ROM

Each RP2040 SoC [31] ships the UF2 compatible [6] bootloader pico-bootrom-rp2040 [13], a native support in silicon. The full source for the RP2040 bootrom at pico-bootrom-rp2040 [13] includes versions B0, B1 and B2 of the bootrom, which correspond to the same silicon revisions, respectively.

Note that every time you build a program for the RP2040, the Pico SDK selects an appropriate second stage bootloader based on what kind of external QSPI Flash type the board configuration you are building for was giving. There are several versions of boot2 [12] for different flash chips, and each one is exactly 256 bytes of code which is put right at the start of the eventual program binary. On Zephyr the boot2 versions are part of the Raspberry Pi Pico HAL [15] module. Possible selections:

CONFIG_RP2_FLASH_AT25SF128A:

boot2_at25sf128a.S [34]

CONFIG_RP2_FLASH_GENERIC_03H:

boot2_generic_03h.S [35]

CONFIG_RP2_FLASH_IS25LP080:

boot2_is25lp080.S [36]

CONFIG_RP2_FLASH_W25Q080:

boot2_w25q080.S [37]

CONFIG_RP2_FLASH_W25X10CL:

boot2_w25x10cl.S [38]

The board set this option to CONFIG_RP2_FLASH_W25Q080.

Further information can be found in the RP2040 Datasheet [32], sections with title “Bootrom” and “Processor Controlled Boot Sequence” or Brian Starkey’s Blog article Pico serial bootloader [14]

Debugging

The board does not provide any SWD connector, thus debugging software is not possible.

Basic Samples

LED Blinky and Fade

WS2812 LED Test Pattern by PIO

See also Zephyr sample: LED strip.

west build -b waveshare_rp2040_zero/rp2040 -p -d build/waveshare_rp2040_zero zephyr/samples/drivers/led/led_strip -- -DCONFIG_SAMPLE_LED_UPDATE_DELAY=500
west flash -d build/waveshare_rp2040_zero

Hint

Neither LED Blinky nor LED Fade can be built and executed on this board, because this system has only one digital RGB LED. A simple GPIO or PWM control is not possible!

Hello Shell with USB-CDC/ACM Console

Hello Shell

See also Bridle sample: Hello Shell.

west build -b waveshare_rp2040_zero/rp2040 -p -S "usb-console" -d build/waveshare_rp2040_zero bridle/samples/helloshell
west flash -d build/waveshare_rp2040_zero

Simple test execution on target

(text in bold is a command input)

BasicsVREGLED StripGPIOADCRTCTimerFlash accessI2CSensors

uart:~$ hello -h
hello - say hello
uart:~$ hello
Hello from shell.

uart:~$ hwinfo devid
Length: 8
ID: 0x9b91758914c92fe9

uart:~$ kernel version
Zephyr version 4.4.99

uart:~$ bridle version
Bridle version 4.4.99

uart:~$ bridle version long
Bridle version 4.4.99.0

uart:~$ bridle info
Zephyr: 4.4.99
Bridle: 4.4.99

uart:~$ device list
devices:
- clock-controller@40008000 (READY)
  DT node labels: clocks
- reset-controller@4000c000 (READY)
  DT node labels: reset
- snippet_cdc_acm_console_uart (READY)
  DT node labels: snippet_cdc_acm_console_uart
- timer@40054000 (READY)
  DT node labels: timer
- uart@40034000 (READY)
  DT node labels: uart0 rp2040mini_serial
- watchdog@40058000 (READY)
  DT node labels: wdt0
- pio@50200000 (READY)
  DT node labels: ((pio_hw_t *)0x50200000u)
- dma@50000000 (READY)
  DT node labels: dma
- gpio-port@0 (READY)
  DT node labels: gpio0
- usbd@50110000 (READY)
  DT node labels: usbd zephyr_udc0
- adc@4004c000 (READY)
  DT node labels: adc
- flash-controller@18000000 (READY)
  DT node labels: ssi
- i2c@40044000 (READY)
  DT node labels: i2c0 rp2040mini_i2c
- pwm@40050000 (READY)
  DT node labels: pwm
- vreg@40064000 (READY)
  DT node labels: vreg
- rtc@4005c000 (READY)
  DT node labels: rtc
- pio-ws2812 (READY)
- ws2812 (READY)
  DT node labels: ws2812 led_strip
- dietemp (READY)
  DT node labels: die_temp

uart:~$ history
[  0] history
[  1] device list
[  2] bridle info
[  3] bridle version long
[  4] bridle version
[  5] kernel version
[  6] hwinfo devid
[  7] hello
[  8] hello -h

References

[1]

https://zephyrproject.org/

[2]

https://www.doxygen.org/

[3] (1,2,3,4,5,6,7)

https://www.python.org/downloads

[4]

https://pypi.org/project/Pillow

[5] (1,2)

https://pypi.org/project/Sphinx

[6]

https://github.com/Microsoft/uf2#user-content-bootloaders

[7]

https://www.sphinx-doc.org/en/master/usage/theming.html

[8] (1,2)

https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html

[9]

https://sitemaps.org/protocol.html

[10]

https://github.com/raspberrypi/usb-pid

[11] (1,2)

https://datasheets.raspberrypi.com/pico/raspberry-pi-pico-c-sdk.pdf

[12]

https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/boot_stage2

[13] (1,2)

https://github.com/raspberrypi/pico-bootrom-rp2040

[14]

https://blog.usedbytes.com/2021/12/pico-serial-bootloader

[15]

https://github.com/zephyrproject-rtos/hal_rpi_pico

[16]

https://www.waveshare.com/wiki

[17]

https://www.waveshare.com/wiki/RP2040-Zero

[18] (1,2)

https://www.waveshare.com/wiki/RP2040-Zero#Documents

[19]

https://files.waveshare.com/upload/5/58/RP2040-Zero.zip

[20]

https://wiki.seeedstudio.com/Grove-Barometer_Sensor-BMP280

[21]

http://www.world-semi.com/ws2812-family

[22]

https://content.instructables.com/F10/WH6U/KQMCJ7I4/F10WH6UKQMCJ7I4.pdf

[23]

https://d2j2m4p6r3pg95.cloudfront.net/module_files/led-cube/assets/datasheets/WS2812B.pdf

[24]

https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf

[25]

https://cpldcpu.wordpress.com/2014/01/14/light_ws2812-library-v2-0-part-i-understanding-the-ws2812

[26]

https://mcuoneclipse.com/2023/04/02/rp2040-with-pio-and-dma-to-address-ws2812b-leds

[27]

https://www.microne.com.cn/en/product/258.html

[28]

https://www.onwaytech.com/static/upload/file/20231009/1696841020308260.pdf

[29]

https://www.winbond.com/hq/product/code-storage-flash-memory/serial-nor-flash/index.html?__locale=en&partNo=W25Q16JV

[30]

https://www.winbond.com/hq/support/documentation/levelOne.jsp?__locale=en&DocNo=DA00-W25Q16JV.1

[31] (1,2,3,4,5,6,7,8,9,10,11,12)

https://www.raspberrypi.com/products/rp2040

[32] (1,2)

https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf

[33]

https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf

[34]

https://github.com/zephyrproject-rtos/hal_rpi_pico/blob/zephyr/src/rp2040/boot_stage2/boot2_at25sf128a.S

[35]

https://github.com/zephyrproject-rtos/hal_rpi_pico/blob/zephyr/src/rp2040/boot_stage2/boot2_generic_03h.S

[36]

https://github.com/zephyrproject-rtos/hal_rpi_pico/blob/zephyr/src/rp2040/boot_stage2/boot2_is25lp080.S

[37]

https://github.com/zephyrproject-rtos/hal_rpi_pico/blob/zephyr/src/rp2040/boot_stage2/boot2_w25q080.S

[38]

https://github.com/zephyrproject-rtos/hal_rpi_pico/blob/zephyr/src/rp2040/boot_stage2/boot2_w25x10cl.S