Hardware DFU


If the OWL becomes completely unresponsive, DFU (Device Firmware Upgrade) mode can be forced by opening the device and doing some manipulations (wires or jumper).

Owl Rev05 and after

Simply move the jumper to the hardware DFU position as shown on the picture below. The Owl will boot in forced DFU mode. Once you have done what you need to do (bootloader and/or firmware update), remember to put the jumper back into its normal position, then close the lid.


Owl Rev04 and under


First, make sure that you can't enter DFU mode using the bootloader: Hold down the LED pushbutton all the while as you plug in the USB cable to a computer. The LED should flash. If this doesn't happen, please read through these entire instructions and make sure you have all the required items at hand, installed, and working.

If you look at the below picture, it shows a diagram of the back of the digital board as it will appear when you remove the lid of the enclosure with the USB connector facing up. You will be able to boot into DFU mode without removing any other parts.

You will need to have dfu-util installed on your computer.

You will also need two short wires, preferably single core (only one wire strand) and with both ends stripped, like the ones you would use in a bread board.

If you have any questions or problems with these instructions, please let us know on the forums. Good luck, and have fun!



First disconnect the USB cable from your computer, but leave it plugged into the device.

Put a wire between BOOT1 and ground - the black line in the drawing. Both holes are empty so the wire will stay in place.

Then put a wire in the 3v3 hole next to ground (third empty hole from the bottom) and reach it over to the BOOT0 pin on the right hand side (7th from the bottom). This is the red line in the drawing. This pin has been soldered, so you will have to touch the wire to the back of the pin as you plug in the USB cable, or hold it in place with a finger.

Before you plug it in, make sure that the two wires in ground and 3v3 (left hand row) are not touching on either side of the board. Move or trim them if necessary. If they touch you will have a short circuit, which is not good at all!

If you find it awkward to fit the wires next to each other then you can use the 3 pin power header on the top left part of the analogue board for one of the wires. Connect BOOT0 to the hole on the analogue board marked 3v3, or BOOT1 to the hole marked gnd. Note that they are not in the same order as on the digital board.

If you can get someone to help you then it’s good to have an extra hand to plug in USB as you hold the wires in place.

Once powered on you may remove one or both wires if you like, but make sure they don’t touch. The device will stay in DFU mode until it resets. When in DFU mode, the LED will be off.

Now check on your computer if it was successful: do dfu-util -l from the command line to see if the device shows up.

It should look something like this:

Found DFU: [0483:df11] devnum=0, cfg=1, intf=0, alt=0, name="@Internal Flash  /0x08000000/04*016Kg,01*064Kg,07*128Kg"
Found DFU: [0483:df11] devnum=0, cfg=1, intf=0, alt=1, name="@Option Bytes  /0x1FFFC000/01*016 e"
Found DFU: [0483:df11] devnum=0, cfg=1, intf=0, alt=2, name="@OTP Memory /0x1FFF7800/01*512 e,01*016 e"
Found DFU: [0483:df11] devnum=0, cfg=1, intf=0, alt=3, name="@Device Feature/0xFFFF0000/01*004 e"

If the wires are not making good contact then it may not have worked. Try again! You can try pressing gently against the wires to ensure good contact with the board as you connect USB.

At this point, you may follow the instructions to Update the Bootloader

(but skip the step to Enter DFU Mode, as you have already done that)

Alternatively you can update the bootloader from within the OwlNest, using Tools / Update Bootloader.


Now it should all be working fine again! Toggling the bypass switch will turn the LED on and off.


Disconnect USB, make sure your wires are removed, and fit the lid back on.

Haven’t got suitable wires? We can post some out to you.