DFU Mode

DFU stands for Device Firmware Update. It’s a special boot mode where the tracker only runs its bootloader, not normal firmware. While in DFU you can flash a new firmware image — including recovery from a botched flash.

You should not enter DFU mode by accident. If you did, follow the exit section below.

When you actually want DFU mode

• A firmware update failed mid-way and the tracker won’t boot normally
• You’re manually flashing a development firmware build
• A firmware-flashing tool tells you to put a tracker in DFU mode

How to enter DFU mode

Press the button 4 or 5 times in quick succession. The tracker enters DFU mode and the LED switches to a distinctive slow flutter pattern.

In this mode the tracker advertises a USB-mass-storage bootloader endpoint. Plug it in over USB-C and your OS will see a small drive (or expose it to the configurator tool).

How to exit DFU mode (you didn’t mean to enter it)

Power-cycle the tracker:

1. Hold the button until any LED activity stops
2. Single-press to power on normally

The tracker boots into normal firmware. Crisis averted.

DFU mode does not erase your tracker

Entering DFU mode is non-destructive. Pairing, calibration, and stored config all survive. The only way to lose those is to actually flash a different firmware image — and even then, re-pairing is fast.

Recovering from a failed flash

If a firmware update failed and the tracker is stuck:

1. Confirm it’s in DFU mode (slow flutter LED, USB drive shows up when plugged into PC)
2. Re-flash via the SlimeVR Server’s firmware update flow with the previous known-good firmware (see Updating Firmware)
3. Flash, wait for completion, power-cycle
4. Re-pair if needed: Pairing

If the tracker isn’t appearing as a USB device at all (no flutter, no drive), check the cable first — many “dead” trackers are dead USB-C cables.