FLY-Micro4 Bootloader (Katapult) Recovery

For brick recovery only

The FLY-Micro4 comes with Katapult pre-flashed from the factory. Do not re-flash the firmware on this page during normal use or when updating Klipper firmware; this page is only for brick recovery after the Bootloader is damaged.

Entering Flash Mode

Power-Disconnected Operation

Before starting, fully power off the printer and disconnect the power supply. Do not plug or unplug wiring harnesses, adjust connector wire order, or touch terminals while power is on.

The BOOT button is circled in the figure:

1. Keep the mainboard completely powered off.
2. Press and hold the BOOT button.
3. Use a USB cable with data transfer capability to connect the mainboard to a computer or host device.
4. Release the BOOT button after the device is recognized.

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Flashing Firmware

• Windows
• Linux / FLYOS

1. Confirm that the device has entered UF2 flashing mode, and a removable disk named RPI-RP2 appears on the computer.

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2. Release the BOOT button or remove the BOOT jumper.

Windows file extension display

Windows may hide file extensions. Please check "File name extensions" in File Explorer, and confirm that you are using .uf2 firmware; do not modify the firmware extension.

3. Download the Flash erase firmware:

• nuke_universal.uf2

Windows 默认可能隐藏文件扩展名。下载后请确认文件扩展名未被修改，不要保存成 .txt 或其他扩展名。

The directory of the erase firmware in the repository is:

FLY-Firmware/RP2040

4. Copy nuke_universal.uf2 to the RPI-RP2 disk to erase the old firmware already present on the device.

5. After the copy is complete, the RPI-RP2 disk will automatically disappear; after the device erases the Flash, it will appear again as an RPI-RP2 USB drive, and at this point the Flash is already empty.

6. Download the FLY-Micro4 Katapult firmware:

• Mico_Katapult_USB.uf2

Windows 默认可能隐藏文件扩展名。下载后请确认文件扩展名未被修改，不要保存成 .txt 或其他扩展名。

The directory of the firmware in the repository is:

FLY-Firmware/MainBoard/Mico

7. Copy the Katapult .uf2 firmware to the newly appeared RPI-RP2 disk.

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8. After the firmware is written, the RPI-RP2 disk will automatically disappear, indicating that Katapult has been flashed successfully.

1. Compile the RP2040 flashing tool. Skip this step if it has already been executed.

cd ~/klipper/lib/rp2040_flash/
make

2. Confirm that the device has entered UF2 flashing mode.

lsusb

If 2e8a:0003 appears in the output, it indicates that the device has entered RP2040 flashing mode. The device name displayed may differ across systems; the USB ID should be used as the reference.

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Device not recognized

Do not continue flashing if 2e8a:0003 does not appear. Please disconnect the device power again and repeat the steps in "Entering flashing mode" on this page.

3. Pull or update the precompiled firmware repository.

• Linux
• FLYOS

First-time download:

cd ~
git clone https://cnb.cool/3dmellow/FLY-Firmware.git

Update the repository if it has already been downloaded:

git -C ~/FLY-Firmware pull --ff-only

First-time download:

git clone https://cnb.cool/3dmellow/FLY-Firmware.git /data/FLY-Firmware
ln -s /data/FLY-Firmware /root/FLY-Firmware

Update the repository if it has already been downloaded:

git -C /data/FLY-Firmware pull --ff-only

4. Flash the erase Flash firmware to clear the old firmware already present on the device:

sudo ~/klipper/lib/rp2040_flash/rp2040_flash ~/FLY-Firmware/RP2040/nuke_universal.uf2

After the command finishes, the device will automatically restart and return to BOOTSEL / UF2 mode. lsusb will show 2e8a:0003 again, and at this point the Flash is already empty.

5. Run the following command to flash the USB Katapult firmware:

sudo ~/klipper/lib/rp2040_flash/rp2040_flash ~/FLY-Firmware/MainBoard/Mico/Mico_Katapult_USB.uf2

6. After the successful flashing prompt appears, proceed with the power-off operation.

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