Insert your SD card into a dedicated USB card reader (avoid built-in laptop slots, as they abstract hardware data).
— Write down your controller model, Flash ID, VID/PID, and original capacity before beginning.
If you cannot find a working download, you can repack official MXTronics firmware yourself using Linux tools. This is legal if you own the original device.
Before downloading anything, identify your exact controller model.
If you are reading this because your first attempt failed, diagnose below: