🛠 First connection and startup of the UEXT-CH390

Objectifs

This tutorial aims to perform the minimal physical connection of the Olimex UEXT-CH390 module to a compatible microcontroller. We will verify that the module receives the correct 3.3V power supply and that the SPI data lines are properly connected, without yet programming the software. This is the fundamental step to avoid wiring errors before moving on to network configuration.

Matériel nécessaire

• An Olimex UEXT-CH390 module.
• A compatible development board (e.g., Raspberry Pi Pico, ESP32-S3, or board with standard UEXT connector).
• A USB cable to power the host board.
• An RJ45 Ethernet cable and a network router or switch.
• A computer for visual verification.

Étapes

The UEXT-CH390 module uses a 10-pin UEXT connector. Ensure your host board has a compatible UEXT or pUEXT connector. If using a board without native UEXT, you will need to use Dupont wires to connect the corresponding pins (SPI MOSI, MISO, SCK, CS, 3.3V, GND).

1. Connector Identification

Gently insert the UEXT-CH390 module into the host board's UEXT connector. Check that pin 1 (usually marked with a triangle or red line on the connector) is aligned with pin 1 on the host board. Pin inversion can damage the module.

1. Physical Connection

Connect the host board to your computer via the USB cable. The UEXT-CH390 module is powered at 3.3V directly from the host board via the SPI bus. There is no specific power LED on the module itself, but ensure the host board is properly powered on.

1. Power Verification

Insert the Ethernet cable into the RJ45 port of the UEXT-CH390 module. The other end must be connected to a LAN port on your router or switch. At this stage, the Ethernet port LEDs may blink if the physical link is established, even without loaded code.

1. Network Connection

Observe the module. Check that no component is heating abnormally. The module measures 50 x 21 mm and should remain cool to the touch when powered on without logical load.

1. Visual Inspection

Vérification

To confirm the connection is correct, you can use a multimeter set to continuity or DC voltage mode. Place the black probe on a GND pin of the UEXT connector and the red probe on the 3.3V pin. You should read a stable voltage close to 3.3V. If the voltage is absent, check that the host board is powered and the connector is properly inserted.

Pour aller plus loin

Once power is confirmed, the next step is to load a test firmware. For Raspberry Pi Pico users, you can compile the lwIP example provided in the SDK. For ESP32 users, the ESPHome firmware with the CH390 component is recommended for quick integration with Home Assistant.