Olimex UEXT-CH390 adds wired Ethernet to Pico and ESP32 boards over SPI

2026-11-12 · Dev boards & ESP32 · Not tested by us

The Olimex UEXT-CH390 is a small open-source SPI Ethernet module for Raspberry Pi Pico/Pico 2 and ESP32 boards that lack wired networking, with Arduino IDE and ESPHome support.

The Olimex UEXT-CH390 adds 10/100 Mbps wired Ethernet to microcontroller boards through an SPI interface. It targets Raspberry Pi Pico and Pico 2 boards, plus ESP32-S3, C3, C5, C6 and other microcontrollers without built-in Ethernet. The module is based on the WCH CH390 Ethernet controller and carries an RJ45 connector, a standard UEXT connector and a smaller 1.0mm-pitch pUEXT connector. It measures 50 x 21 mm.

For builders, the useful part is the controller detail: the WCH CH390 integrates a 10/100 Mbps Ethernet MAC and PHY, supports 10BASE-T and 100BASE-TX with auto-negotiation and Auto-MDIX, and includes 16KB SRAM for packet buffering. It also ships with a factory-programmed MAC address, so you do not need to provision one externally. Olimex supports the module in the Arduino IDE and ESPHome firmware, which makes it relevant for wired IoT sensors and Home Assistant devices where WiFi is unreliable or unwanted.

For builders. The module is relevant where SPI is free and a UEXT or pUEXT header fits; Arduino IDE and ESPHome are the supported firmware paths.

Not tested by us. This is a reading of the public sources below, not a hands-on review. Check the source pages before you buy, build or upgrade.

Sources

[1] CNX Software — https://www.cnx-software.com/2026/11/06/olimex-uext-ch390-spi-to-ethernet-module-targets-raspberry-pi-and-esp32-mcu-boards-running-esphome/. Read 2026-11-12.

Source pages read 2026-11-12. See how we label claims.

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