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FLY-Gemini V3 Bootloader Recovery

For brick recovery only
  • Please note that the HID Bootloader is pre-flashed at the factory, so there is no need to flash it again.
  • For regular firmware updates, please prioritize using the USB firmware or USB bridge CAN firmware page. Do not repeatedly flash the bootloader firmware.

Entering DFU Mode​

Power Off Operation

Before starting, completely turn off the printer and disconnect the power supply. Do not plug or unplug wiring harnesses, organize interface wiring, or touch terminals while the system is powered on.

  • There are two ways to enter DFU mode.

  • First method: With the motherboard completely powered off, use a jumper cap to connect BOOT and BOOT1. Then, connect one end of a data-capable USB cable to the motherboard and the other end to the computer.

  • The second method involves a reset sequence and is not recommended for general users to perform independently. If after-sales support requests this method, please follow the steps provided by the after-sales team.

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Flashing Firmware​

  • Gemini bootloader firmware
  • You can obtain the firmware via the following link:
  • The firmware can be found at
FLY-Firmware/MainBoard/Gemini

  • Turn DIP switches 3 and 4 ON, and connect the host computer's USB to the onboard Type-C port.

  • Turn DIP switches 1 and 2 OFF, otherwise, it will affect the connection between the host computer and the board.

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Power Off Operation

Before connecting or re-plugging the USB cable, completely shut down the printer and disconnect other power sources. Do not allow the tool board to be powered simultaneously via the printer's power supply and the USB interface.

USB Connection Compatibility

Some computer USB ports may cause unstable flashing due to driver or signal compatibility issues. If connection fails, try switching to a different USB port on the computer or use a reliable USB hub. If the error shown below appears, check the USB connection and drivers first.

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  1. Download and install SetupSTM32CubeProgrammer and the STM32 DFU driver from the Auxiliary Software Download Page.
  2. Save the firmware downloaded from this page to a location on your computer that is easy to find.
Windows File Extension Display

Windows may hide file extensions. Please check "File name extensions" in File Explorer to confirm the firmware is still in .bin or .hex format. Do not modify the file extension.

  1. Confirm the device has entered DFU flashing mode according to the product tutorial, then connect it to the computer using a USB cable that supports data transfer.
  2. Open STM32CubeProgrammer, select USB mode, refresh the device list, and connect.
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  1. If no error popup appears, the connection is successful.
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  1. Click the download icon on the left side, and check the flashing options as shown in the image below.
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  1. Click Browse and select the firmware to be flashed.
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  1. When flashing .bin firmware, set Start address to 0x08000000. When using .hex firmware, keep the address embedded in the file.
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  1. Click Start automatic mode to begin flashing.
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  1. When the success message appears, the firmware flashing is complete.
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