Hikvision DVR bricked after firmware upgrade

[pogt 0]

I upgraded my Hikvision DVR (DS-7216HQHI-K2) yesterday and broke the DVR. I think I have uploaded the wrong firmware to the DVR and caused the DVR to not functioning properly. After I uploaded the new firmware into the DVR, the DVR showed successful message and rebooted. However, now at the login screen, the username is empty, even the Admin id which used to be there is gone.

 

Without able to login, I cannot downgrade the firmware from the GUI. I managed to connect to the DVR console using the USB-TTL UART converter, however after I pressed ctrl+u when booting, I managed to stop the autoboot process, but the screen just stop there with the prompt HKVS$ and nothing else. I type printenv, help and etc., nothing displayed.

 

Could anyone help please? Your help is greatly appreciated.