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Topic: TP-LINK TL-WR740N v 4 bricked when restoring back to factory Firmware

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Hello Everyone,

I need help recovering a TP-LINK TL-WR740N v4.23 , which was bricked dead when when restoring back to factory Firmware from Open-Wrt  .

After upgrade button click on Open-wrt firmware with factory reset done ,now router dead and When i powered up, all lights are on and off simultaneously after few seconds. I waited about 1 hour but router did not respond any ip address and does not show any connections on Network And Control center Also, I don't know what was the IP address of it.

please help me Experts...I need help

Regards
jenisbob

This exactly happened to me too, when I have flashed factory firmware WITH uboot, which is wrong. Theres no way how to tell if the firmware contains uboot, except it's a bit bigger. You should have used the first released firmware, that contains no uboot I think.

This router does not have firmware recovery via tftp, so you will have to replace it, if it´s still in the warranty, or open the case, solder serial and recover via nokia ca42 serial cable. How to do this is in the wiki http://wiki.openwrt.org/toh/tp-link/tl-wr740n - see debricking.

nozombian wrote:

This exactly happened to me too, when I have flashed factory firmware WITH uboot, which is wrong. Theres no way how to tell if the firmware contains uboot, except it's a bit bigger. You should have used the first released firmware, that contains no uboot I think.

This router does not have firmware recovery via tftp, so you will have to replace it, if it´s still in the warranty, or open the case, solder serial and recover via nokia ca42 serial cable. How to do this is in the wiki http://wiki.openwrt.org/toh/tp-link/tl-wr740n - see debricking.

Dear nozombian,
MY  Router version 4.23  is not in warranty for now....so i want to open and case and solder serial port and recover using nokia c-42 or Dku 5 seeing this wiki link but all pictures of version 4.23 is not so clear to soldier on which port....so i need full details to recover my router..but i am not getting any useful tips to recover my router from EXPERTS too....
so i am so disappointed ...

Thanks
Jenisbob

I am not getting any useful tips to recover my router from EXPERTS too....
so i am so disappointed ...

Thanks
Jenisbob

Hi,

I did something similar with my TP-link 1043ND.

Basically you have to take it apart an solder on 4 wires as pictured in
http://wiki.openwrt.org/toh/tp-link/tl-wr740n

Go on ebay and buy yourself a USB to Serial device, mine cost about £3, make sure it has both 3.3V and 5V modes.

Then plug that in to you PC and connect the wires you soldered on to your router board.

Then follow the general debrick instructions to get going again.

I am a newbie and it took me about 5 or 6 hours to debrick the router, it is not quick or easy, but it can be done it you try.

I'll try to help more if you want, but you'll need those wires soldered on and the RS 232 to USB converter (unless your PC has a serial port?)

bushrod wrote:

Hi,

I did something similar with my TP-link 1043ND.

Basically you have to take it apart an solder on 4 wires as pictured in
http://wiki.openwrt.org/toh/tp-link/tl-wr740n

Go on ebay and buy yourself a USB to Serial device, mine cost about £3, make sure it has both 3.3V and 5V modes.

Then plug that in to you PC and connect the wires you soldered on to your router board.

Then follow the general debrick instructions to get going again.

I am a newbie and it took me about 5 or 6 hours to debrick the router, it is not quick or easy, but it can be done it you try.

I'll try to help more if you want, but you'll need those wires soldered on and the RS 232 to USB converter (unless your PC has a serial port?)

Dear Bushrod,
I opened router case and found exactly like that on ver 4.23 pictures but picture is not so clear to be soldered ..i am sure i will fry my router if i solder any wrong wires...
i want to try with Nokia C-42 or Dku 5 cable but can't find proper guidance ,,,,please guide me..

hope i will get video link to recover my router

Thanks
jenisbob

What detailed tips from experts are you expecting, when it´s in the wiki already?

There´s detailed image (on the wiki page I have posted) where to connect what, just look closely to the picture: http://wiki.openwrt.org/_media/toh/tp-l … jpg?cache=

Just don´t forget to connect tp18 and tp28 with a wire to have all serial pins working. Nokia pinout is here: http://pinouts.ru/CellularPhones-Nokia/ … out.shtml, for newbies here: https://www.youtube.com/watch?v=9pumxmUyfuI

nozombian wrote:

What detailed tips from experts are you expecting, when it´s in the wiki already?

There´s detailed image (on the wiki page I have posted) where to connect what, just look closely to the picture: http://wiki.openwrt.org/_media/toh/tp-l … jpg?cache=

Just don´t forget to connect tp18 and tp28 with a wire to have all serial pins working. Nokia pinout is here: http://pinouts.ru/CellularPhones-Nokia/ … out.shtml, for newbies here: https://www.youtube.com/watch?v=9pumxmUyfuI

Dear nozombian,
Thanks for useful links that i am searching for.....very thankful
Now can i connect any usb cable or Iphone data cable or
i have to use Nokia DKU-5 cable only for 3.3 v?
please guide me in simple steps because i am newbie to these steps...

Thanks
Jenisbob

I have tested only with ca 42 cable, but you can use dku 5 as well I think, for my wr741nd it is allowed to use both, wr740n and wr741nd routers are almost the same. If you have to buy one, get ca 42, if you have by hand dku 5, try it wink About iphone cable I have no info, but you might try google, if you have it by hand.

(Last edited by nozombian on 16 Feb 2013, 16:07)

nozombian wrote:

I have tested only with ca 42 cable, but you can use dku 5 as well I think, for my wr741nd it is allowed to use both, wr740n and wr741nd routers are almost the same. If you have to buy one, get ca 42, if you have by hand dku 5, try it wink About iphone cable I have no info, but you might try google, if you have it by hand.

Dear Nozombian,

Thanks for more infos..

hope i will unbrick my router tomorrow ...i will buy ca-42 and try those steps to soldier too....
may i have to connect wire to VCC near ground or
i have to  connect TX RX and Ground only?

then after i connect those wires and connect usb cable to computer usb port... open PUTTY sotware to Telnet to 192.168.1.1 on port 23 ....please guide me after these steps...

sorry to say that i am newbie to these steps...

thanks for guidance
jenisbob

You need just rx tx and gnd, I think it can be seen on the video link I gave you.

nozombian wrote:

You need just rx tx and gnd, I think it can be seen on the video link I gave you.

Dear Nozombian,

Thanks for more infos..

then after i connect those wires and connect usb cable to computer usb port... open PUTTY sotware to Telnet to 192.168.1.1 on port 23 ....please guide me after these steps...

sorry to say that i am newbie to these steps...

thanks for guidance
jenisbob

I have also found that all 4 wires are connect to RX TX GND VCC......i am confused about connecting to VCC ...

Please guide me viewing attached wiki pictures of Tplink Wr740N version 4.23........

http://wiki.openwrt.org/toh/tp-link/tl-wr740n

Thanks
jenisbob

VCC is just power source, I don't know what for, but you will really need only 3 wires. If you don't believe me, read http://wiki.openwrt.org/doc/hardware/po … .listening wink

All you have to do to connect the router via serial cable can be seen in the video, there's not much more I can tell or describe you. You will use putty, but you will have to set it to use serial port and write port name - which one it is you will find in device manager after connecting the cable (if you are using windows), so no telnet to ip yet, have you watched the video at all? Debricking section and how to upload firmware via tftp is in the other link, just read it *carefully*, don't worry if it's for different router, most of the procedures are common, you will only have to use different firmware image, exactly the one for your router and revision.

Don't worry the theory, it's normal to be afraid of new things, but at least please read those wiki articles, there's no much sense in writing it down here with my own words, there are mostly written with far better English than I could tell you wink When you will have the cable ready, soldered and router communicating, you will be more clever, you'll see. When you exactly ask, what part you do not understand, there are many good people in here trying to help, but if you will not read yourself what was given to you, no one can help help you.

Openwrt is fun at the first place and fun costs money, worst what can happen is, that you will lose $17 worth your device. Many people in country where I live are working the whole day to earn that, but if you will learn, you will manage that - with a bit of skill and good luck wink

nozombian wrote:

VCC is just power source, I don't know what for, but you will really need only 3 wires. If you don't believe me, read http://wiki.openwrt.org/doc/hardware/po … .listening wink

All you have to do to connect the router via serial cable can be seen in the video, there's not much more I can tell or describe you. You will use putty, but you will have to set it to use serial port and write port name - which one it is you will find in device manager after connecting the cable (if you are using windows), so no telnet to ip yet, have you watched the video at all? Debricking section and how to upload firmware via tftp is in the other link, just read it *carefully*, don't worry if it's for different router, most of the procedures are common, you will only have to use different firmware image, exactly the one for your router and revision.

Don't worry the theory, it's normal to be afraid of new things, but at least please read those wiki articles, there's no much sense in writing it down here with my own words, there are mostly written with far better English than I could tell you wink When you will have the cable ready, soldered and router communicating, you will be more clever, you'll see. When you exactly ask, what part you do not understand, there are many good people in here trying to help, but if you will not read yourself what was given to you, no one can help help you.

Openwrt is fun at the first place and fun costs money, worst what can happen is, that you will lose $17 worth your device. Many people in country where I live are working the whole day to earn that, but if you will learn, you will manage that - with a bit of skill and good luck wink

Dear nozombia,
Thanks for everything that you have done to me ...i really thankful to you what you have done and guided  to me....
i will try all those steps and let you know about how i have done  ...and  the router's processing ...

Regards
jenisbob

Dear nozombia,
I got my Nokia Dku-5 cable and i cut off cable and found only three cables only.....now i am fully confused too ..
and also when i plugged on cable on Windows 7 laptop ,no driver of DKU5 is supporting  on Device manger....USB-UART COntroller is marked as Yellow ? icon...please guide me ....

Regards
jenisbob

You will have to install the cable driver first, if you have windows, but don't expect me to lead you by hand, you seem to be missing elementary knowledge how do things work, so if you don't know something, try to write a question to google.com search bar first and you will see you can find some how-to for beginners.

Quick google gave me this: http://fileforum.betanews.com/detail/No … 06613223/1

Of course, that dku 5 is different from ca 42, so why have you bought the dku 5? You might have perfectly seen, how to do it with ca42, now you will have to find by pinout page to assign the correct pins, or you will have to find another video with dku 5 cable, if there's such. I don't have this cable, so I can't tell you which color comes where, but you should find it yourself anyway, because colors of different cable manufacturers might differ, so be sure to dissassemble the nokia pop port to see which color is connected to what pin and write it down before you will unsolder them and connect to your your router.

I connected cables and installed Dku-5 driver too...and in device manager it is showing Ports Com3 and when i launched Putty ..i get errors after few seconds:

I connect on Com3  Speed 115200  Data 8 bits Parity None Flow Control None
but when i connect usb cable and boot router ..it response and on Putty screen commands are showing about Auto rebooting,  Etho up etc as that upper link Videos ....then after 30 seconds of showing these commands My SYStem Crashes...I tried on Windows 7 and Windows XP too but same happens at last /..

Please guide......
I don't know how can i post Pictures or Videos of those command s...

jenisbob

Congratulations, you are almost done, except for that system crashing, that should not happen, ever! Maybe you have a bad driver for the cable, try to find different one.

When you see the listing from a console, there should be a second or so pause, where you have time to write "tpl" to get to the console. Then go by these steps: http://wiki.openwrt.org/toh/tp-link/tl- … tp.install Dont forget, that you will have to use firmware for your router, because the how-to is for a differeent model, but otherwise it's the same.

First you will have to install tftp server though, there you will have to put your firmware image. I have never used tftp server on windows, but google found http://tftpd32.jounin.net/ and it sounds good.

(Last edited by nozombian on 18 Feb 2013, 16:49)

nozombian wrote:

Congratulations, you are almost done, except for that system crashing, that should not happen, ever! Maybe you have a bad driver for the cable, try to find different one.

When you see the listing from a console, there should be a second or so pause, where you have time to write "tpl" to get to the console. Then go by these steps: http://wiki.openwrt.org/toh/tp-link/tl- … tp.install Dont forget, that you will have to use firmware for your router, because the how-to is for a differeent model, but otherwise it's the same.

First you will have to install tftp server though, there you will have to put your firmware image. I have never used tftp server on windows, but google found http://tftpd32.jounin.net/ and it sounds good.

Dear nozombian,
I have tried with different cable drivers too but same result as System Crash...

I will upload video in YouTube tomorrow and post that link here so that You and other Experts can guide me to recover my Router....

Is there any linux tips so that i can try?

Regards
jenisbob

I'd suggest to install ubuntu, cable works out of the box, at least ca 42 worked for me. You can try to boot live usb distro first, but you will also need to install tftp server and I don't know if you will succeed with installing anything, when you are running only live usb. From linux terminal you can connect to router via command "screen /dev/ttyUSB0 115200" (or some other ttyUSBnumber), or you can use putty as on windows.

Dear nozombian,
I have tried with different cable drivers too but same result as System Crash...I tried many nokia dku-5 drivers not success upto now..can you please guide me about dku-5 drivers....and also can i use linux to do all these recovery steps? please guide...

There's something wrong with your windows or drivers, maybe some part of a corrupted driver is still present, it might be sometimes hard to get rid of the wrong drivers. You can try some old system restore point, from before you ever used the cable, then try other driver, restore again, and so on.

On linux, it should be much easier, download ubuntu live image and burn live dvd, or create live usb flash disk with utility from pendrivelinux. I don't know, if you can install some missing packages onto live usb, but you should give it a try.

nozombian wrote:

This exactly happened to me too, when I have flashed factory firmware WITH uboot, which is wrong.


Hello,

The latest firmware for TL-WR740N V4 that can be downloaded from here http://www.tp-link.com/en/support/downl … version=V4 is:

wr740nv4_en_3_16_6_up_boot(130529).bin


I found on TL-WR741ND site (which has very similar hardware to TL-WR740N) http://wiki.openwrt.org/toh/tp-link/tl-wr741nd that to restore original firmware from OpenWRT, you need to cut first 0x20200 bytes from original firmware if it contains boot in it's name, so the procedure is like this:

scp wr741nv1_en_3_9_18_up_boot(100104).bin orig.bin root@192.168.1.1:/tmp

cd /tmp
mv wr741nv1_en_3_9_18_up_boot(100104).bin orig.bin
dd if=orig.bin of=tplink.bin skip=257 bs=512

mtd -r write /tmp/tplink.bin firmware

1. Would this method work for TL-WR740N V4 and firmware wr740nv4_en_3_16_6_up_boot(130529).bin as well?
2. Is the amount of bytes that needs to be cut the same?


I'm asking, because I want to install OpenWRT on my TL-WR740N V4, however I'd like to have possibility to go back to original firmware without bricking the router.


Thanks in advance for your answers!

Looking forward,
Przemek.


P.S. I've just found on dd-wrt forum thread about restoring default firmware http://www.dd-wrt.com/phpBB2/viewtopic. … 483#421483 and it is written there:

2) Cut-off the first 0x20200 bytes so that the resulting file starts with the hex sequence:
01 00 00 00 54 50 2D

However, when I open wr740nv4_en_3_16_6_up_boot(130529).bin in hex editor, it starts with 01 00 00 00 54 50 2D  without any modification, so do I really need to cut first 0x20200 bytes from original firmware with dd if=orig.bin of=tplink.bin skip=257 bs=512???

(Last edited by przemnet on 12 May 2014, 22:39)

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