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W55RP20 Serial to Ethernet Official Design Guide

Introduction

The W55RP20 combines WIZnet’s W5500 Ethernet controller and Raspberry Pi’s RP2040 MCU, designed specifically for Serial-to-Ethernet applications supporting UART TTL, RS-232, RS-422, and RS-485 communication.

Pinout Description

Setting Pin

PinPinoutNameDescription
RST29RUNMCU Reset (Active Low)
BOOT Mode21GP15Firmware boot mode control
AT Mode20GP14Enter AT command mode (Active Low)
RP BOOT63BOOTFlash reset & RP2040 boot (Active Low)
232/485 Select18GP12Low: TTL/RS-232, High: RS-422/485
Factory RST40GP18Reset IP settings (Firmware retained)
  • RST Pin : This pin is used for MCU reset and operates in an Active Low state.

  • BOOT Mode : PinDesigned to control the boot mode of the Serial to Ethernet internal firmware.

  • AT Mode Pin : Operates as Active Low; controlling this pin allows entry into AT command mode via serial for chip control.

  • RP BOOT Pin : The reset pin for internal flash memory, operating as Active Low, following the RP2040 boot sequence.

  • 232/485 Select Pin : Determines the communication method based on its state at initial chip operation.

    • Low: Sets UART or RS-232 mode
    • High: Sets RS-422 or RS-485 mode
  • Factory RST Pin : Resets the IP settings to factory defaults while keeping the firmware unchanged.

Data Pin

The selection between SPI mode and UART mode can be determined at boot by reading the state of the UART_SPI_SEL pin.

PinPinoutNameDescription
UART_SPI_SEL19GP13UART/SPI interface select pin
High:SPI, Low/NC:UART

UART mode

PinPinoutNameDescription
UART_TX9GP4UART data transmission.
UART_RX10GP5UART data reception.
UART_RTS12GP7UART request to send (flow control)
UART_CTS11GP6UART clear to send (flow control)
UART_DTR14GP8UART data terminal ready (flow control)
UART_DSR15GP9UART data set ready (flow control)
  • UART_RTS Pin: UART request to send (flow control); determines communication mode (floating for RS-485, Low for RS-422)

SPI mode

PinPinoutNameDescription
SPI_SCK67GP2SCK input pin for Data SPI transmission
SPI_MISO68GP3MISO pin for Data SPI reception
SPI_MOSI9GP4MOSI pin for Data SPI transmission
SPI_CSn10GP5SPI Chip Select pin
SPI_INT46GP26SPI Master Recv data pending pin

LED Indicators - Status

PinPinoutNameDescription
RUN41GP19MCU status LED, blinks when the MCU is operating normally.
PHY LINK16GP10Indicates PHY link status
TCP Conectoin17GP11Indicates active TCP connection

Firmware Upload

Three firmware upload methods:

  • USB (UF2)

    • Set RP-BOOT pin Low and reset; drag Boot.uf2 and then app.uf2 into ‘RPI-RP2’ drive.
  • SWD (J-Link)

    • Upload HEX/BIN files using J-Link, same as standard RP2040.
  • Ethernet (BIN)

    • Use WIZnet Configuration Tool for application updates only (not initial upload).

MAC Address Setup

Initial firmware upload via USB/SWD required. MAC setup essential via WIZnet MAC Tool (115200 baud). MAC address must be purchased separately.

Configuration

Advanced settings and further configurations available using the latest WIZnet Configuration Tool.