Make sure to select the correct version, depending on whether you have the H or H4 variant. The wrong firmware makes the device unusable for the time being. You can still write the firmware directly on the chip, but you will need the appropriate hardware.
At the time of this post, version 1.0.64 was current. Here you need to download the file with the extension .dfu:
NanoVNA H / H4 in DFU mode and install driver
First, the NanoVNA H4 must be set to DFU mode: To do this, press the joystick in the middle and switch on the device. The screen should now remain black.
With the NanoVNA H, the DFU mode is started via the Config Menu.
Now the NanoVNA H4 can be connected to the computer via USB. Probably the USB driver is missing in the Device Manager.
Then the driver must be installed in the device manager from the DFU installation path via the device manager. You can find it here: C:\Program Files (x86)\STMicroelectronics\Software\DfuSe v3.0.6\Bin\Driver\Win10
Now DfuSeDemo can be started from the start menu.
Firmware Flash with DfuSE
In the DfuSE, the lower “Choose Button” must then be clicked:
Now the just downloaded firmware file can be selected:
With a click on “Upgrade” the firmware is now updated:
Please make sure to select the correct firmware. If you flash the firmware without H4 on a NanoVNA H4, the device is defective for the time being. You can still write the firmware directly on the chip, but then you need the appropriate hardware.