Thonny must be set to the MicroPython (ESP32) interpreter and the right COM port, and the board must have MicroPython firmware flashed.
What the message means
A blank ESP32 has no MicroPython on it, so there is no prompt to connect to. The interpreter choice and port also have to match.
Fix it in this order
- Use a USB cable that carries data, and check that a COM port appears.
- In Thonny open Run > Configure interpreter and choose MicroPython (ESP32) and the port.
- Use the “Install or update MicroPython” option in the same window to flash the firmware if the board is new.
- If flashing fails, hold the BOOT button while it connects.
- Press the stop button or Ctrl+C to interrupt a running program.
- Close other programs that use the same port.
If you see this, do this
| You see | Do this |
|---|---|
| No port in the list | Cable or driver. |
| Port found, no prompt | Firmware missing. Flash it. |
Related
failed to connect, USB driver.
Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.