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FLY-SHT36/42 Bootloader (Katapult) Recovery

For Brick Recovery Only

FLY-SHT36/42 ships with Katapult pre-flashed. Do not re-flash the firmware on this page during normal use or Klipper firmware updates; this page is intended solely for brick recovery after bootloader corruption.

Firmware Description​

Name Explanation

Katapult was formerly known as CanBoot, and both names may appear simultaneously in older tutorials or firmware names.

Katapult is a bootloader used to boot and update Klipper:

  • Katapult itself cannot be used as a Klipper MCU; after flashing, you still need to write Klipper firmware that matches the hardware and communication method.
  • Supported tool boards can enter Katapult by quickly double-pressing the RESET button; after entering, there is usually a status light blinking.
  • CAN, RS232, and USB use independent Katapult firmware; you cannot simply modify file names or mix them directly.
  • For CAN firmware, you must also select the correct bus speed, with common speeds being 500K and 1M.
  • This page applies to the STM32F072 version of the FLY-SHT36/42.
  • This page provides Katapult firmware for two CAN rates: 500K and 1M.
CAN Rate Must Match

Select only one firmware that matches your actual CAN network rate. The host, mainboard, and all CAN devices on the same bus must use the same rate.

Entering Flash Mode​

Power Off First

Before starting, completely power off the printer and disconnect the power supply. Do not plug or unplug wiring, organize interface cable order, or touch terminals while powered.

The figure marks the BOOT pads:

  1. Keep the toolboard completely powered off.
  2. Use a jumper cap to short the BOOT pads.
  3. Connect the toolboard to your computer or host using a Type-C cable that supports data transfer.
  4. Once the device is recognized, remove the BOOT jumper cap.
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Flashing Firmware​

Download the FLY-SHT36/42 Katapult firmware:

The firmware directory in the repository is:

FLY-Firmware/ToolBoard/SHT36
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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Finishing the Flash​

Power Off First

After flashing is complete, disconnect the toolboard USB and external power before removing the BOOT jumper cap and restoring normal wiring. Do not plug or unplug toolboard wiring while powered.

After powering back on, the status LED will blink when Katapult starts normally:

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