Sucessfully debricked WNDR3700v2 using Jtag cable !!!

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dolezelk
DD-WRT Novice


Joined: 01 Jul 2011
Posts: 3

PostPosted: Thu Jul 21, 2011 9:44    Post subject: Sucessfully debricked WNDR3700v2 using Jtag cable !!! Reply with quote
I have accidentally loaded firmware image into u-boot area, so my WNDR was comlete brick. So no reset-debrick method was working as u-boot(ala CFE) was overwritten.

Using Openocd, JTAG cable and building my own u-boot from GPL source downloaded from NetGear, I was finally able to debrick my WNDR3700v2 today. ( 3 days of hard work) guess same method can work on many other router types which are not supported by tjtag.

I will summarize and probably post on wiki, as it is a bit complicated.
Anyone interested, let me know. Smile
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Jonny_doe
DD-WRT Novice


Joined: 11 Aug 2008
Posts: 32
Location: South West U.K.

PostPosted: Thu Jul 21, 2011 20:28    Post subject: Reply with quote
nice work m8 Wink
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nFamous
DD-WRT Novice


Joined: 17 Feb 2011
Posts: 17
Location: /dev/eth0

PostPosted: Thu Jul 21, 2011 21:27    Post subject: Reply with quote
Congratulations for the successful debricking!

I think that a tutorial for this approach would be nice, regarding the many bricked WNDRs which occurred with the latest builds.
Of course it's a rather special procedure, but a tutorial on how to do this would be helpful, just for the case someone gets in the same situation. Wink

Best regards,
nFamous
dolezelk
DD-WRT Novice


Joined: 01 Jul 2011
Posts: 3

PostPosted: Thu Jul 21, 2011 22:01    Post subject: Reply with quote
basic approach is this:

- you need bufered Jtag cable (wiggler style) or USB types
- OpenOCD latest snapshot from trunk (stable version -0.4 does not work with atheros - it is bugged)
- GPL package from NetGear to build your own u-boot
- then you have to build 2 versions of u-boot - one that will reside in RAM on 0xa0100000 address and second that will reside in flash at 0xbf000000. I have those two version of u-boot compiled already so I can provide binary
- they you connect to your wndr3700 using openocd using parport.cnf and ar71xx target
- perform reset, halt, reset init
- load RAM version of U-boot at address 0xa0100000
- set breakpoint at 0xa01004c8
- resume 0xa0100000
- after bp is reached, you shall hold reset button until you are able to ping the router from you conputer
- then you upload modified openwrt image ( mtd0 writable, not 'ro') image using TFTP (can provide modified image)
- wait some time until router resets several times

then perform all the steps above again with the exception that you will not hold the reset button

After all it will boot the kernel.
then you can telnet, upload final version of U-boot into /tmp , do mtd write ....

All done Smile)
after reboot it shall come back in....
navas
DD-WRT Novice


Joined: 11 Nov 2015
Posts: 6

PostPosted: Wed Mar 23, 2016 20:11    Post subject: Reply with quote
Hi,

I have WNDR4300, it is failing at u-boot (checksum mismatch error) after a power failure, can you please help me restoring my device, I found one article in google, but it was chinese and talks a new u-boot alternative called "Breed"

http://www.right.com.cn/forum/thread-170402-1-1.html
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