Cfeon Q23b-104

We made it!

After thousand of tests, passing by a serial tftp boot, trying jtag reprogramming we finally get back the wr841nd (ver.8.1) to life!


We followed an OpenWRT guide that you can find over here

Well… we disassembled the flash of another working router with a very small soldering iron tip (all the merit goes to Edo).

Then we connected to the serial of the router via an arduino adapter. Doing this we cuold connect to uboot (remember the “tpl” keys for getting to the uboot console!!).

From the console we dumped all the files of the flash into the ram with the command:

The command is: copy the content of the flash (0x9f000000) to the ram (0x81000000) for the lenght (0x3effff)

Then we reassembled the old broken flash and copied all back in that one with the command:

And doing this we restored uboot in the broken flash. After this we reinstalled OpenWRT via the tftp server mode with the following commands:

Finally we had a working router!



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  1. Andrei #
    December 13, 2014

    I got a similar problem,my WR841ND Ver 8.2 is bricked, and I don’t really know how to unbrick it. I cannot get to the safe mode (by pressing the reset button), although I could before. I have order a (USB To RS232 TTL UART PL2303HX Auto Converter USB to COM Module Cable HS) but I don’t see any output when I’m listening to it using putty. Currently when I turn it on, only the first led is on and nothing else is blinking. How can I check if the serial cable is working? Is it possible to copy an “image” (from PC) of the working flash to the router RAM through a serial cable? You probably did something similar but used an arduino adapter and a working flash.

    • December 15, 2014

      Hi Andrei,
      did you connect it to the serial “pins” ?
      What we did was a little bit different. At first we tried to unbrick the router via serial port by downloading through FTP the bin image and copying it to the memory. Since we were a little bit tired we given in input the wrong address to write. The router was totally bricked, but the serial port was still telling something. At this point we’ve taken another router, unsoldered the flash while the router was running (because it copies all the firmware inside the ram at boot) soldered the corrupted flash and copied the content of the ram (so the right firmware) inside the corrupted flash. Made the switch between flashes again and everything was back to normality.
      Try to use an arduino instead.

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