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Katapult (Bootloader) Firmware

Pre-flashed at Factory

The FLY-SHT36/42 is pre-flashed with Katapult at the factory. Do not re-flash the firmware on this page during normal use or Klipper firmware updates; this page is only intended for 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 the firmware that matches the actual CAN network rate. The host machine, motherboard, and all CAN devices on the same bus must use the same rate.

Entering Flash Mode​

Power Off Required

Before starting, completely power off the printer and disconnect the power supply. Do not plug or unplug wiring, arrange interface cables, or touch terminals while powered on.

The BOOT pad is indicated in the figure:

  1. Keep the tool board completely powered off.
  2. Use a jumper cap to short the BOOT pad.
  3. Connect the tool board to a computer or host machine using a Type-C cable that supports data transfer.
  4. After the device is detected, remove the BOOT jumper cap.
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Flashing the 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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Completing the Flash​

Power Off Required

After flashing is complete, disconnect the tool board's USB and external power first, then remove the BOOT jumper cap and restore normal wiring. Do not plug or unplug the tool board wiring while powered on.

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

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