How can I enter DFU mode on flight controllers, in particular on my CL Racing F4S flight controller?

Ref.: https://cl-racing.myshopify.com/products/clracing-f4s


2 Answers 2


There are three ways you should know to enter DFU mode.

The first, as mentioned before, is to push down the bootloader button and power on your board.

The second method is to be used on boards that don’t have a bootloader button (which is increasingly rare). You will need to bridge two bootloader pads on your flight controller to enter DFU mode. Check the specific diagram for your flight controller to find out exactly what pads you need to bridge.

The last method is to enter the CLI and type either ‘DFU’ or ‘BL’, which will then put the FC into DFU mode. Obviously this method won’t work if you’re entering DFU mode because you ant connect to your computer.

  • $\begingroup$ There is another way that has worked for me in the past, when unable to enter DFU mode. Download the ImpulseRC Driver Fixer app. Disconnect USB from the drone, shut down Betaflight (assuming Betaflight is being used, but it should work for other flight controller firmware). Reconnect all and run the ImpulseRC Driver Fixer app. impulserc.blob.core.windows.net/utilities/… $\endgroup$
    – Schome1
    Commented Apr 19, 2020 at 14:07
  • $\begingroup$ @Schome1 good to know, thanks $\endgroup$ Commented Apr 19, 2020 at 14:09
  • $\begingroup$ There's an important caveat to the last method you mention that might be good to note. If you're using a serial-based radio receiver (s.bus, spektrum satellite, etc) and it is connected to certain UARTs on the flight controller, it can disrupt DFU. Basically DFU will initialize on the UART where it gets chatter from the RX rather than the VCP needed by the firmware flashing utility. The solution is to makes sure the RX is not powered on, or not connected. Then DFU should initialize as expected. $\endgroup$
    – QuadMcFly
    Commented Apr 20, 2020 at 13:34

You can enter DFU mode by pressing the boot button and powering the board on.

Entering DFU mode can be necessary when you want to flash/update the board's firmware. Especially, when you get "Failed to open serial port" in the Betaflight configurator.


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