Re: DS-7604NI-E1/4P, DS-7608NI-E2/8P and DS-7616NI-E2/16P Firmware V. 3.3.6 Build 15
Hikvision NVRs do not respond to
TFTP in the same manner as IPCs. A TTL-level serial connection (not RS-232 level) is required to unbrick these devices via the white 4-pin UART connector on the main logic board. With IP cameras, simply throwing up the Hikvision TFTP server with the proper firmware loaded into that directory is sufficient. Power on the camera, set the IPs accordingly, and done. It's a fairly straightforward recovery process once everything is set up correctly. NVRs are not the same. I've recovered many of these NVRs (the 3.1.x to 3.4.x upgrade bricks them every time) and all of them appear to be the same. While they still require TFTP for the transfer of the firmware itself, it's not automated like the IP cameras are.
IPCs have a version of U-Boot that within the first n seconds of power on, probe the network for a TFTP server at 192.0.0.128. If found, connect as client and attempt to pull digicap.dav, (The firmware), flash it, and reboot. (Sometimes the reboot doesn't happen I've found). In any case, that is an automated process.
NVRs on the other hand must be invoked manually. You need to PuTTY over serial/TTL directly into the boot loader to manually halt it. Once U-boot is stopped, there are a few prompts asking you for info. At this point, make sure your computer and recorder are both connected to your main network (no 192.0.0.128 necessary). It will ask you to set an IP for the recorder, then specify the IP of your TFTP server (your computer). It will start the firmware recovery process once you hit enter. It will not reboot after it's done, it requires hitting Enter in PuTTY over serial to finish it off (or a power cycle will work too).
What is remaining in my NVR stock from last year have already been bricked and firmware upgraded, so I'm not touching those again, but a friend of mine has a 7608 that is in need of a firmware upgrade which will result in a brick. I will write a step by step post sometime this week and link it here using that recorder. Details, screenshots and all. Give me until Friday. Have a few other things on my plate at the moment.