Question about USB flashing.

[rastod101]

Hello,

I am a student currently working on my diploma thesis, which is focused on the Nordic nRF52840. I have designed a custom board that is functioning well. At the moment, I am flashing it using a J-Link programmer, but I would like to utilize the D+ and D- lines of the USB interface.

My VS Code project is based on the Nordic nRF52840 DK, along with my custom overlay. Is it possible to flash the board and read data directly via the USB? Currently, I am only using the USB port for power, but in my design, I have connected the D+ and D- pins.

Thanks,

[Hung Bui]

Hi Rastislav, 

The nRF52840 is not designed to be programmed via the USB D+ and D- pin. It has to be flashed using the SWD interface as described in the specification. 
However, it's possible to make a DFU bootloader that can receive the image via the USB either as USB interface or a virtual COMport interface and then replace the original application with the new image. 
This is how we do it with the nRF52840 dongle. Take a look here: https://docs.nordicsemi.com/bundle/ncs-latest/page/zephyr/boards/nordic/nrf52840dongle/doc/index.html

Note that this solution is better suite for flashing final image as it doesn't provide any way of debugging and it take longer time to do flashing compare to the traditional way of flashing via a programmer.