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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 reconnecting the USB cable, completely turn off the printer and disconnect all other power supplies. Do not let the tool board be powered simultaneously through the printer power supply and the USB interface.

USB connection compatibility

The USB interfaces on some computers may cause unstable flashing due to driver or signal compatibility issues. If the connection fails, try using a different USB interface on the computer or use a reliable-quality USB dock; when the error shown below appears, also check the USB connection and driver 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 on this page to a location on your computer that is easy to find.
Windows file extension display

Windows may hide file extensions. In File Explorer, check "File name extensions" to confirm that the firmware is still .bin or .hex, and do not change the file extension.

  1. Confirm that 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 pop-up appears, the connection is successful.
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  1. Click the download icon on the left, and check the flashing options as shown in the figure 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 included in the file.
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  1. Click Start automatic mode to begin flashing.
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  1. When the success prompt appears, the firmware flashing is complete.
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