Entering DFU mode switches port number

Question

When switching the dongle into DFU mode, it changes the serial port number when running in windows. 
 Both the bootloader and the application sets up the USB and calls the app_usbd_serial_num_generate(); 
 As I read the doc I expected the usb to keep its port number when going into dfu mode. Is this a windows 
 feature or am I doing something wrong ? 
 /Jimmy

bjorn-spockeli · Accepted Answer

Hi Jimmy, 
 the nRF52840 Dongle is preprogrammed with the Open Bootloader with DFU example, which requires a signed image 
 The private key that the public key in the preprogrammed Open Bootloader on the dongle is not distributed. So in order to update the bootloader on the nRF52840 Dongle you actually do need a programmer. 
 Best regards 
 Bjørn

Entering DFU mode switches port number

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