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Help & Troubleshooting
GimbalDoctor — Help
How to install, how to use it, and how to fix every issue — step by step.
The app works — tested on real aircraft
Almost every connection problem comes from the PC setup: the USB driver, the cable, or a Windows security policy. There is a fix for each one below.
GimbalDoctor — Windows
Most common connection fix: WinUSB driver (Zadig)
If the drone is detected but won't connect — error “Cannot open device”, “LIBUSB_ERROR_NOT_FOUND”, or the interface is on the libusb0 driver — install WinUSB on the service interface:
- 1Download Zadig from zadig.akeo.ie and run it as administrator.
- 2Connect the powered-on drone with a USB data cable.
- 3In Zadig, open Options → List All Devices.
- 4Select the DJI interface “(Interface 4)” — VID 2CA3, PID 0020, MI_04.
- 5Set the target driver to WinUSB and click Replace Driver.
- 6Close Zadig and click Connect in GimbalDoctor — the drone connects over USB Direct.
This is safe and reversible — it does not change the drone's firmware. Models that connect over COM (Mini 2, Mini 3, Mini 4K, Mini SE) do not need this step.
Installation & first steps
Up and running in a few minutes.
Requirements
- Windows 10 or 11, 64-bit.
- A USB data cable (not charge-only).
- An internet connection for activation and service firmware.
How to install
- Download the installer from the GimbalDoctor page (“Download for Windows”).
- Run the setup — it installs the app and the USB driver (approve the UAC/admin prompt).
- Open GimbalDoctor and enter your license key GD-XXXX-XXXX-XXXX.
First connection
- Power the drone on and connect it with a USB data cable.
- Click Connect — the app configures the service connection itself.
- The drone model and firmware versions appear automatically.
What you can do now
Everything that already works in the current version.
Gimbal calibration
- Joint Coarse, Linear Hall and Advanced calibration — after a motor replacement or a calibration error.
- Remove the gimbal cover first and keep the drone still.
- Live gimbal angles are shown while you work.
Install service firmware
- Download and flash factory/service firmware for supported models, straight from our server.
- Every file is verified with SHA-256 before flashing.
- Don't unplug the drone or close the app during flashing; use a fan on long flashes.
Install other firmware
- On supported models you can flash a different firmware version over COM/USB (e.g. roll back or re-flash).
- Only use firmware intended for that exact model.
- Keep the battery charged and don't interrupt the process.
Clear error 40021 (Gimbal IMU)
- Resets the gimbal IMU data to clear error 40021.
- Works on all tested models.
Read errors (HMS)
- The “HMS / Errors” tab reads the fault codes the drone reports and translates them into a readable description.
- Lets you tell a gimbal problem from a motor-controller (ESC) or camera problem before opening the drone.
Diagnostics & serial numbers
- Per-module firmware versions, vision & TOF sensors, serial numbers and smart-battery status.
Connection problems
The drone is on and plugged in but still won't connect.
The drone is not detected at allCable / port
- Use a USB data cable — not a “charge-only” one. This is the most common cause.
- Plug the cable into the drone's USB-C port, not the remote controller.
- Power the drone on and let it boot first, then connect.
- Try another cable and another USB port — ideally straight into the PC, no hub.
“Cannot open device” / “LIBUSB_ERROR_NOT_FOUND”Driver
- The drone's interface is on the wrong driver (e.g. libusb0) or WinUSB is missing.
- Fix: install WinUSB with Zadig — see the “Most common fix” box above.
“Drone in use by DJI Assistant” or ACCESS / BUSY errorOther app
- Close DJI Assistant 2 and any other software using the drone.
- Unplug and replug the drone, then click Connect.
- If needed, run GimbalDoctor as administrator.
Connects, then drops after a moment (USB read error / device not connected)Cable / power
- This is usually the cable or power, not the app.
- Use a short, good-quality data cable — no extensions or hubs.
- Don't let the drone go to sleep; keep the battery charged.
- Don't move the cable during an operation.
“No DUML response on any TCP port” (RNDIS)Usually normal
- For Mini 3 Pro and Air 2 this message is normal — those drones have no DUML over TCP.
- It means the USB link wasn't bound correctly — fix the driver (WinUSB / Zadig).
USB driver — how it works and how to undo it
How the driver works
- GimbalDoctor talks to the drone over a service USB channel. For some models it installs the WinUSB driver on one drone interface so the app can open that channel.
- It only changes that one interface — it does not reflash or modify the drone.
- The change is fully reversible.
Revert to the original driver so DJI Assistant sees the drone againImportant
- After using GimbalDoctor, DJI Assistant 2 may not see the drone until you revert the driver.
- Easiest: in GimbalDoctor use “Uninstall driver”, then unplug and replug the drone — Windows restores DJI's original driver.
- Or in Device Manager: find the DJI device/interface → Uninstall device → unplug and replug; Windows reinstalls the original driver.
- Or in Zadig: Replace Driver back from WinUSB to the original driver.
- COM models (Mini 2, 3, 4K, SE) are unaffected — DJI Assistant always sees them.
“Install USB Driver” does nothing / “An Application Control policy has blocked this file”Smart App Control
- Your Windows has Smart App Control / Application Control enabled, which blocks the driver installer.
- Best fix: install the driver manually with Zadig (WinUSB on Interface 4) — it bypasses the block.
- Alternatively: Windows Security → App & browser control → Smart App Control → Off. Note: once off, it can't be turned back on without reinstalling Windows.
- On managed/company PCs (WDAC / AppLocker) the administrator must allowlist the app.
UAC asks for administrator permission
- Click “Yes”. Installing the driver needs administrator rights — just once.
License & activation
Where is my license key
- The GD-XXXX-XXXX-XXXX key is emailed automatically once the payment clears.
- It is also shown in your order history on drone-partss.com.
“Invalid key” or “expired”
- Check that you typed the key exactly, including the dashes.
- The license is valid for the purchased period (2 months or 1 year). Buy a renewal in the shop — the key stays the same.
- Activation requires an internet connection.
How many computers per license
- One license = one computer. To move it to another PC, contact support.
Updates
How the app updates
- Updates install automatically — no need to download the installer again.
- New models and features are included in the same license, at no extra cost.
An update won't install
- Close and reopen the app while connected to the internet.
- If it still fails, download the latest installer from the site and install over the top — license and settings are kept.
Error codes (HMS)
What the error codes mean
- The “HMS / Errors” tab translates the codes the drone reports into a readable description.
- ESC codes (e.g. 16080041 / 42, 16100019) point to a motor-controller problem, not the gimbal.
Error 40021 (Gimbal IMU)
- Use the gimbal IMU data reset — it clears error 40021 on all tested models.
Codes 10016 / 10017 and othersComing soon
- Codes like 10016 and 10017 are camera-side faults, not the gimbal.
- Full decoding and guided fixes for these are in preparation — see “Coming soon”.
Model notes
Mini 2, Mini 3, Mini 4K, Mini SE
- They connect over a COM port — no WinUSB driver or Zadig needed.
- If not detected, check Device Manager for a new COM port.
Mini 3 Pro, Air 2S, Air 2, Mini 4 Pro
- They connect over USB bulk (WinUSB). If they won't connect, fix the driver with Zadig (Interface 4).
Mavic 3 series
- Fully supported: diagnostics, HMS error reading, serial numbers and gimbal calibration.
Coming soon (version 3.0.0)
In preparation — included in the same license, at no extra cost. Order and availability may change.
Motor test (ESC)
- Test each drive motor individually, through its ESC.
Gimbal motor test
- Test the gimbal motors (pitch, roll, yaw) after a replacement or a movement error.
CALI tools
- Edit calibration files: TOF and vision sensor serials, repair after a sensor swap.
More error codes (10016, 10017, …)
- Expanding the HMS decoder with more codes and guided fixes, including camera faults 10016 / 10017.
Still not working?
In the app, click “Send to Support” — it builds a diagnostic report and gives you a case number. Send us that number and we'll check exactly what's happening.
Contact support · [email protected]Include your drone model, Windows version and the case number from the “Send to Support” button.