Linksys E4200 Serial/JTAG Port Guide

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immi803
DD-WRT Novice


Joined: 17 Mar 2018
Posts: 20

PostPosted: Tue Mar 20, 2018 13:38    Post subject: Reply with quote
wab wrote:
Hi everybody,

this my first time ever to participate in the forum and I wanted to share my experience and take the opportunity to thank everyone for their help.

I have been using ddwrt for a long time, but eventually I managed to brick my router because I got lazy and didn't do my home work before the upgrade.

So I have E4200v1 router running dd-wrt.v24-31924_NEWD-2_K3.x_mega-e4200.bin and for some reason https was not working (I have tried different releases), and last week I found a couple of new releases and decided to go for the latest (I know that newer is not always good) Rolling Eyes
Once rebooted, the router started bootloop and only getting 4-7 ttl100 responses at a time.

After panicking, I managed to find an Ethernet cable and started searching the forum and landed on this http://www.dd-wrt.com/phpBB2/viewtopic.php?t=310880 which clearly states not use this release on broadcom chips Rolling Eyes

Then found this post and started following the instructions using the following:
1- Raspberry pi (wheezy) + minicom
2- pwr and hdd led cables from an old case



Quote:
sudo minicom -b 115200 -o -D /dev/ttyAMA0
nvram erase
flash -ctheader : flash1.trx

I have used tftp.exe to send the firmware.
Quote:
go

but then router stopped responding, nothing worked no Lan ports no reset nothing, the serial was showing this http://www.dd-wrt.com/phpBB2/viewtopic.php?p=889405

So I had no choice but to go for the jtag, and my setup was like this



PIN(3)--(TDI)---100ohm---PIN(2)
PIN(5)--(TD0)---100ohm---PIN(13)
PIN(7)--(TDI)---100ohm---PIN(4)
PIN(9)--(TDI)---100ohm---PIN(3)
PIN(6)--(GND)------------PIN(20)

downloaded the cfe template and followed instructions from here http://www.dd-wrt.com/phpBB2/viewtopic.php?p=889405:
I used Hirensbootcd to boot into mini win XP and downloaded brjtag v2.0.5

Quote:
1. probe
brjtag -probeonly /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5

2. erase CFE
brjtag -erase:cfe /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose

3. erase kernel
brjtag -erase:kernel /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose

4. erase NVRAM
brjtag -erase:custom /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose /window:1c000000 /start:1cff0000 /length:10000

5. flash CFE
brjtag -flash:cfe /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose /noerase

6. backup the CFE
brjtag -backup:cfe /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose

7. backup NVRAM
brjtag -backup:custom /cable:dlc5 /fc:120 /noreset /nobreak /instrlen:5 /wx8 /verbose /window:1c000000 /start:1cff0000 /length:10000

8. reboot the e4200 and perform a serial recovery
This time I used windows tftp to send the firmware.

9. You have a revived E4200 v1.

Finally, I have successfully unbricked my router:)


Congrats, you're a success story man Very Happy

please can you elaborate how you edit Mac address, serial number and Pin ? this may be a noob question but if you make video or complete elaboration for that, help would be highly appreciated

Secondly, i couldn't find pin string mentioned in link you shared, can you please mention pin offset number?

i re-lived my hope to revive my old baby finally Smile
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immi803
DD-WRT Novice


Joined: 17 Mar 2018
Posts: 20

PostPosted: Wed Mar 21, 2018 21:11    Post subject: Reply with quote
Guys!!!! Very Happy

i've finally unbricked it, Following this below mentioned guide

https://www.dd-wrt.com/phpBB2/viewtopic.php?p=889394

Yes!! you can unbrick it , below are some pics of my Setup, though it look clumpsy but it was very solid, i using pins and NO Solidering of anything

https://ibb.co/bHdoaH
https://ibb.co/jVg8aH
https://ibb.co/mrTX2x
https://ibb.co/e6TbUc
https://ibb.co/ekrKhx

Here is also a little video of CFE flashing Very Happy

https://youtu.be/9-GdcDOACPc

Happy Debricking Very Happy

Thanks to all Devs, Gurus and everyone out there to help me out Smile
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