The compact SPI-to-Ethernet module adds 100Mbps wired networking to Raspberry Pi Pico, Pico 2 and compatible ESP32 boards.
Olimex has introduced the UEXT-CH390, a compact hardware module that adds wired Ethernet connectivity to microcontroller development boards without a native Ethernet interface. Designed around WCH CH390 SPI to Ethernet Controller, the module has a capability to achieve the data speed of up to 100 Mbps. It is intended for use with the Raspberry Pi Pico and Pico 2 boards, and ESP32 modules, including ESP32-S3, ESP32-C3, ESP32-C5, and ESP32-C6. It is an alternative to the Wi-Fi connection through the wired network .
The module has dimensions of 50×21mm and features a standard UEXT and an additional 1mm pitch pUEXT interface. The module uses SPI for communication with the host microcontroller and supports 10BASE-T and 100BASE-TX Ethernet connections. The CH390 controller has packet buffering and a preprogrammed MAC address. The module receives its 3.3V supply through the UEXT or pUEXT connector, simplifying integration with compatible development boards.
Olimex has also developed an RP2040 driver for ESPHome, extending CH390 support to Raspberry Pi Pico-based systems. A demonstration using the RP2040-PICO30U-16 board provides DHCP networking, automatic discovery in Home Assistant and over-the-air firmware updates after the initial USB programming. The company also provides a separate Raspberry Pi Pico SDK example using lwIP and a small web server, allowing developers to build network-connected applications without ESPHome.
The UEXT-CH390 is open-source hardware, with KiCad design files, schematics, firmware and software examples available on GitHub. Developers can examine and modify the hardware design or adapt the software for their own embedded applications.
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