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    Bricked TpLink WDR4300 router advice and question

    Good day folks. Someone brought in a WDR4300 which keeps rebooting. Before writing this, I did my obligatory self-research beforehand and found a very interesting video which I'm definitely going to try and follow. See it here.
    At the moment, I'm not really asking for advice on the router's issue itself, but rather on something I noticed in the video: the guy uses an UART to USB board to hook up to the router. At first I thought I don't have one of those, but then I thought about it more carefully and realised I might actually have one already just under a different form: what I have is one of those E-bay serial programmers which I normally used for working with TV EEPROMs and SPIs, but I noticed it's got the required pins: TX RX and also 3.3v, so is one of THESE similar to the one used in the video (albeit physically different obviously). Has it also got UART ? Sorry if this is a stupid question - I'm fairly new to programing. I'm more of a hardware guy. If so then I'm going to go for it and report back in case I get stuck and REALLY need help, for now let's just get this out of the way...can't really start working if I don't have the required tools
    Last edited by Dannyx; 10-19-2017, 08:38 AM.
    Wattevah...

    #2
    Re: Bricked TpLink WDR4300 router advice and question

    yes, you use a usb-serial with ttl outputs.
    you dont use the 3.3v pin, just tx,rx and gnd.

    Comment


      #3
      Re: Bricked TpLink WDR4300 router advice and question

      The problem I'm currently facing is that my laptop does not recognize the CH341A as a COM port so I can't select it in putty...trying to work around this. CH341A is capable of UART too right ? Still not entirely sure I have what I need :|
      Wattevah...

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        #4
        Re: Bricked TpLink WDR4300 router advice and question

        Just to make sure: THIS is what I got.
        Attached Files
        Wattevah...

        Comment


          #5
          Re: Bricked TpLink WDR4300 router advice and question

          please ignore wrong thread sorry
          Last edited by vinceroger69; 10-20-2017, 05:56 AM.

          Comment


            #6
            Re: Bricked TpLink WDR4300 router advice and question

            I figured it out (for now anyway): there's a small jumper cap you have to remove to swtich from I2C to UART or something like that. Even after the fact, I had to search pretty deep for the driver, since the package that came with the programmer only had the drivers for when you're using it in SPI mode...again, I'm sorry if I mess up all these protocols and interfaces, I'm by no means a pro....I2c, Serial, UART, parallel...while we're at it, could someone perhaps clear this up a bit please ?
            Wattevah...

            Comment


              #7
              Re: Bricked TpLink WDR4300 router advice and question

              you should have searched here for ch341 - i have posted the full drivers and software etc.
              AND a pinmap and info about the jumper!

              Comment


                #8
                Re: Bricked TpLink WDR4300 router advice and question

                Ok guys update: I managed to connect up using PUTTY like the guy did, but didn't get the same looping messages as in the video. Instead, mine kept loading messages for like 1 minute then finally stopped and showed "PASSWORD" which didn't happen in the guy's vid so I didn't really know what to do at this point. I tried every combination possible but couldn't go any further, so I just stopped it, unplugged the router and decided to go again. This time though, upon plugging the router in, I noticed it actually booted up ! It no longer looped and could even connect up to it with the default settings...AWESOME I have no idea what the heck happened buy who cares
                Wattevah...

                Comment


                  #9
                  Re: Bricked TpLink WDR4300 router advice and question

                  I've had a D-Link that I bricked with DD-WRT. I used a TTL, booted the router and punched in " clear NVRAM " enter. Thing rebooted with D-Link firmware, so I reloaded DD-WRT and all was good. Mine didn't ask me for a password though...

                  Comment


                    #10
                    Re: Bricked TpLink WDR4300 router advice and question

                    Oh yeah, guess what: the guy called yesterday saying he bricked it again.....he claims he just brought it home, plugged it in and went into boot-looping straight away, but I'm having a hard time believing it just broke down like that after a tested it barely minutes before he called...most likely he tried resetting it or loading dd wrt or some junk....good job, now I have to do it again and I'm not sure whether I'll be as lucky as to simply connect the programmer and get it going again
                    Wattevah...

                    Comment


                      #11
                      Re: Bricked TpLink WDR4300 router advice and question

                      Yeah, it's obviously not going to work a second time. The same thing happened again today: connected up via serial, the router "unbricked itself" once but died after it rebooted after the initial configuration via its GUI. Now it just keeps looping and I can't stop it, so I don't know what I'm going to do...
                      Wattevah...

                      Comment


                        #12
                        Re: Bricked TpLink WDR4300 router advice and question

                        No matter what I'm typing, the router just goes through its sequence and eventually displays restarting system in the serial monitor and keeps going...have no idea how to stop it...typing TPL like the guy says does nothing - occasionally I see it's saying incorrect password....
                        Wattevah...

                        Comment


                          #13
                          Re: Bricked TpLink WDR4300 router advice and question

                          THIS is what I get in Putty's serial monitor. After "rebooting system" the cycle repeats. When it decided to work the first time around (when I got really lucky and seemed to fix itself), it stopped at "user". Now it won't do that any longer...I also noticed this part which doesn't seem right insmod: cannot open module `/lib/modules/2.6.31/kernel/x_tables.ko': No such file or directory...
                          Attached Files
                          Wattevah...

                          Comment


                            #14
                            Re: Bricked TpLink WDR4300 router advice and question

                            Had another idea: given that the firmware files provided for this router are BIN files, I SHOULD be able to rip out the SPI chip and flash it on the computer like I do with some TVs, then put it back in and hope for the best. Even though I can back-up whatever is already on that chip, I think it's much safer to use a blank chip and flash that, while leaving the original one intact as it is...that way, if something goes wrong I can put it back and at least get it back to its original state...
                            Wattevah...

                            Comment


                              #15
                              Re: Bricked TpLink WDR4300 router advice and question

                              I'd hazard a guess that it's booting from part of the firmware that's working and then trying to write a working version to the other part of the chip and it's failing for some reason. This can happen if someone badly modifies a firmware and uploads it to a device, it can over write parts that it wasn't supposed to, breaking the factory reset/fall back mode.

                              Comment


                                #16
                                Re: Bricked TpLink WDR4300 router advice and question

                                If it's the flash memory then I have no way of programming that....if it's the small 8 pin SOIC then it might still be salvageable which is what I'm trying to do atm..
                                Wattevah...

                                Comment


                                  #17
                                  Re: Bricked TpLink WDR4300 router advice and question

                                  bootloader is o.k. so you can flash it through the serial link.
                                  but i would check the caps first - they are a big problem in routers.

                                  Comment


                                    #18
                                    Re: Bricked TpLink WDR4300 router advice and question

                                    You're saying the booloader is OK because the router "boots" and does some stuff ? I'm not a master programmer so I have virtually no idea how it works, except a very basic one so this is also a good learning experience. How can I flash something if the router doesn't stop looping ? It won't accept anything I type into it, even if I spam TPL TPL TPL, it just says "password" and if I happen to type TPL at that point it says invalid login and keeps on going with its sequence - there's no stopping it. One problem I see with writing a blank SPI chip and installing it in place of the one already on the router is the MAC addresses will no longer match (at least with the very brief knowledge that I've got)...don't know if that's the case or those parameters are stored someplace else and won't be affected. Not entirely sure if it will work at all, obviously. The software I use to flash SPI chips for TVs seems to open the firmware file just fine, but whether that's actually the file that resides ON that SOIC is a whole different story, since nobody seems to have done it this way. At the end of the day, it's a 25q64 chip so my ch431 thing a ma-jig handles those.

                                    You don't say, bad caps Well that one be one hell of a ride if all it had was a faulty cap....so as not to waste time blindly replacing all caps, are there any particular ones on there I should look out for ? There's 6 of them. I mean the router appears to work, so can a cap cause it to reboot when it reaches the same part every time ? The more you learn.......

                                    Also ignore that jumper wire sticking out of the board - that's just a CD audio cable I hacked to connect to the serial programmer since it already had the female header at one end which matched the GND/TX/RX pins on my CH431
                                    Attached Files
                                    Last edited by Dannyx; 10-26-2017, 07:42 AM. Reason: Added details
                                    Wattevah...

                                    Comment


                                      #19
                                      Re: Bricked TpLink WDR4300 router advice and question

                                      Often the boot sequence can be escaped, that is, you can press a key/combination of keys to escape the process thus allowing you to interact with the bootloader. Or, you can invoke a TFTP boot process, making the device boot from the LAN, allowing it to load up then you can reflash it via it's web interface.

                                      You could also put OpenWRT on it, see if it functions as expected, then re-flash it back to stock firmware. https://wiki.openwrt.org/toh/tp-link/tl-wdr4300 This page also covers TFTP loading.

                                      Comment


                                        #20
                                        Re: Bricked TpLink WDR4300 router advice and question

                                        there are only 6 caps - replace the 4 smaller ones.

                                        https://wiki.openwrt.org/toh/tp-link/tl-wdr4300

                                        Flashing via TFTP

                                        Pressing the WPS/Reset button during powerup makes the bootstrap loader enter the TFTP recovery mode. The procedure can be used to transfer a firmware image:
                                        assign 192.168.0.66 to your local network interface (the router uses 192.168.0.86)
                                        publish a firmware image via tftp: cp openwrt-ar71xx-generic-tl-wdr4300-v1-squashfs-factory.bin /srv/tftp/wdr4300v1_tp_recovery.bin
                                        configure your tftp server
                                        wait for the firmware transfer (about 20s), firmware flash (about 90s) and subsequent reboot (about 30s)
                                        Last edited by stj; 10-26-2017, 09:18 AM.

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