WSAL20410 – Pico-ETH-CH9121/en

Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

Summary

The Pico-ETH-CH9121 is a converter that enables serial communication over the network. It uses the CH9121 chip and provides two independent UART channels with configurable network operating modes (TCP/UDP). The module connects via a standard Pico header and can be configured via software or serial commands.

Related products at JW Tech

WSAL20410 – Ethernet to UART Converter for Raspberry Pi Pico, 10/100M Ethernet

Technical overview

Two independent UART channels with transparent transmission between UART and Ethernet.
Four operating modes: TCP Client, TCP Server, UDP Client, UDP Server.
By default, UART 2 is disabled; UART 1 operates in TCP Client mode.
Default values: IP 192.168.1.200, target IP 192.168.1.100, device port 2000, target port 1000, baud rate 9600, 8 data bits, 1 stop bit, no parity.
Power supplied via VSYS input (3.3 V / 5 V); operating temperature range -40 °C to 85 °C.
Automatic MDI/MDIX detection and auto-negotiation (10/100 Mbps, full/half duplex).
Configuration via NetModuleConfig.exe on the host PC or via serial commands.
Pin mapping: RXD1→GP0, TXD1→GP1, RXD2→GP4, TXD2→GP5, CFG0→GP14, RST1→GP17.

Commands and examples – verify before use:

sudo apt-get install p7zip-full
sudo wget https://files.waveshare.com/upload/5/5a/Pico_ETH_CH9121_CODE.7z
7z x Pico_ETH_CH9121_CODE.7z -o./Pico_ETH_CH9121_CODE
cmake -DPICO_BOARD=pico -DPICO_PLATFORM=rp2040 ..
make -j9
cp main.uf2 /media/pi/RPI-RP2/

Notes and version constraints

The exact Pico SDK version and path variables must be adapted to the local environment.
When flashing, the BOOTSEL button must be held while connecting the USB cable.
To use a screen, the mini jumper on CFG0 must be removed.
To restore factory settings, short the RESET pads and power-cycle the module.
The complete list of AT commands is not fully included in the source text; it must be referenced from the datasheet.

Source and revision record

Pico-ETH-CH9121 - Waveshare Wiki
Source revision: 102649
Captured: 2026-09-02T03:47:53+00:00
SHA-256: 876590522d2c0ffec0fd0a86c0bc81c2d02d2aacabecdcb5ce8ca5dc4eda8c16