Px4(hkust_nxt-dual)on nucelo-h753zi usb com port issue

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I flashed h7 bootloader on nucelo-h753zi, i can confirm bootloader is working by led blinking,but i when i do make hkust_nxt-dual upload it waits for bootloader infinitely,later i discoverd my com port itself is not detected(on nucelo board we have stlink debugger com port and user usb port).i suspect something regarding usb should be configured in px4 first,i have seen many post saying ppl have dumped code on nucelo-f767.is there documentation on this?