I'm having some trouble flashing CircuitPython to my Circuit Python Express. I successfully enter boot mode (LEDs are all green and red D13 light slowly blinking) but I can't flash anything. When I drag and drop a .uf2 file, there's no response even though I see the .uf2 successfully copied to the CPE drive. Eventually, CPE exits boot mode and returns to flashing rainbow lights. When I double click reset to enter boot mode again, the file I had dragged and dropped is gone.

Has anyone encountered something like this before?

  • Hello hvnova, "has anyone encountered this before" is probably not really the question you're asking. You'll get better help when you ask what you're trying to achieve, e.g. how to flash the chip.
    – Helmar
    Jan 16, 2023 at 8:48

1 Answer 1


This is the expected behavior. It's not an error.

When you drop a .uf2 file on the virtual disk, the bootloader stores the firmware in a different section of the flash memory. It's pointless to keep the .uf2 file around; it would just waste space.

There is a response - the drive disconnecting while the firmware is copied and then reconnecting without the .uf2 file is the response.

To verify that the firmware was correctly installed look at the file boot_out.txt on the CIRCUITPYTHON drive. You should see two lines that look something like this:

Adafruit CircuitPython 7.3.3 on 2022-08-29; S2Mini with ESP32S2-S2FN4R2
Board ID:lolin_s2_mini

Of course the version number and the board identifier will depend on what version you installed to what board you installed it on.

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