Full unbrick tutorial for TP-Link TL-WR941ND router???

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erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Sat Nov 27, 2010 17:38    Post subject: Full unbrick tutorial for TP-Link TL-WR941ND router??? Reply with quote
I am searching all over this forumand the Openwrt forum but nowhere to find complete tutorial with instructions and tools needed to unbrick my TL-WR941ND router. I have installed Openwrt to it and now there is no connection to it through LAN ports. I know now that I need a serial cable but I am unable to find somewhere the complete tools needed for this job. Can somebody provide me?

I am newbie in this field and this is my first router flashed with Openwrt. It flashed successfully but I was configuring it and saved the settings but it died now. I have done after this one Linksys WRT54GL successfully and this one is working well but no chance to achive ethe goal that I need. To change TTL. I found some instructions how to change TTL but they are not working for this Linksys. But primarily I need now to revive this TP-link router .
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toto2700
DD-WRT User


Joined: 22 Aug 2010
Posts: 66

PostPosted: Sat Nov 27, 2010 19:15    Post subject: Re: Full unbrick tutorial for TP-Link TL-WR941ND router??? Reply with quote
You should get a Nokia CA-42 cable. You can find on Ebay.
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TL-WR1043ND v1.7 Openwrt
TL-WR841ND v3.0 Openwrt
TL-WR741ND v1.9 Openwrt
buddee
DD-WRT Guru


Joined: 06 Feb 2010
Posts: 7401
Location: Little Rock

PostPosted: Sat Nov 27, 2010 19:55    Post subject: Reply with quote
yes ca-42 cables are very cheap on ebay or amazon, then you can reference this wiki, just make sure to look at the pinouts on the unit itself.

http://www.dd-wrt.com/wiki/index.php/Serial_Recovery

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epek
DD-WRT Novice


Joined: 28 Oct 2010
Posts: 27

PostPosted: Sun Nov 28, 2010 0:24    Post subject: Reply with quote
I had similar experiences with an almost bricked WR-1043ND.

- Just in case you are unsure if it´s bricked or not -

configure your pc lan to 192.168.1.2
keep pinging 192.168.1.1
power cycle the router

if you get at least one answer ping, there is still a failsafe mode using the front button.

power cycle the router, wait until sys-led starts flashing, then press the front button.

sys will blink faster, telnet is now available on 192.168.1.1

you can then flash using mtd.

-excerpt from the openwrt wiki

probably this router behaves similar
erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Mon Nov 29, 2010 12:15    Post subject: Reply with quote
So, I should not connect the 3.3v in this pinout here http://www.dd-wrt.com/wiki/index.php/Serial_port_pinouts coming from CA-42 cable to router board?

And is it risky to try RX, TX directly on board till I connect to HyperTerminal or Putty? I don't think that I can damage the router this way without any voltage, just RX, TX and GND pins
buddee
DD-WRT Guru


Joined: 06 Feb 2010
Posts: 7401
Location: Little Rock

PostPosted: Mon Nov 29, 2010 12:50    Post subject: Reply with quote
erreterr wrote:
So, I should not connect the 3.3v in this pinout here http://www.dd-wrt.com/wiki/index.php/Serial_port_pinouts coming from CA-42 cable to router board?

And is it risky to try RX, TX directly on board till I connect to HyperTerminal or Putty? I don't think that I can damage the router this way without any voltage, just RX, TX and GND pins


Most times with a CA-42, there is no 3.3v line because its self powered, most cases the CA-42 has 3 lines in it... Rx, Tx, GND, which is all you'll need. The ca-42 cable mainly saves you from having to worry about running the cable with a breakout board for lvl shifting, they have that built in.

Also if you get the rx/tx reversed on hooking it up to the board is no problem, it doesn't mess anything up, just gives you garbage output.

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epek
DD-WRT Novice


Joined: 28 Oct 2010
Posts: 27

PostPosted: Mon Nov 29, 2010 19:22    Post subject: Reply with quote
Just out of curiosity -
How exactly did you brick it?

I had - as stated above - a similar experience when updating openwrt via opkg, but was more fortunate.
buddee
DD-WRT Guru


Joined: 06 Feb 2010
Posts: 7401
Location: Little Rock

PostPosted: Mon Nov 29, 2010 21:43    Post subject: Reply with quote
Also, as a pointer, if you order the cable, once you get it, before you just splice off the end and build the cable, make sure you either slowly disassemble the end jack and trace the lines and match them up with the pop-port mapping, or have a multi-meter on hand (which is how i did it) I found the multi-meter technique much easier.

http://www.hardwarebook.info/Pop-Port

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erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 18:26    Post subject: Reply with quote
to epek
As I stated in the first post I was configuring openwrt and saved some settings but when I restarted the router then it was inoperational.

to all
Can somebody help me now I managed to log onto router via serial console and using a mobile phone box called "Infinity BOX" as a serial interface and not the CA-42 because I thinked that it should work and it worked also, but now when I logged I used the command

firstboot, then
mtd erase nvram

and the router was resetted successfully and I managed to log onto router via web interface, but as I was nervous with that system I go to immediately flash the original firmware from TP-LINK via LuCI, but it just hanged there and I saw that the router just restarts continously. Now when I logged via serial interface I have this output in HyperTerminal:
erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 18:28    Post subject: Reply with quote
Resetting...

U-Boot 1.1.4 (Mar 8 2010 - 10:28:58)

AP81 (ar7100) U-boot
DRAM:
sri
32 MB
id read 0x100000ff
flash size 4MB, sector count = 64
Flash: 4 MB
Using default environment

In: serial
Out: serial
Err: serial
Net: ag7100_enet_initialize...
No valid address in Flash. Using fixed address
bsingle_phy = 0
eth0: 00:03:7f:09:0b:ad
eth0 up
eth0
Autobooting in 1 seconds## Booting image at bf020000 ...
Uncompressing Kernel Image ... Error: Bad gzipped data
GUNZIP ERROR - must RESET board to recover

Resetting...

U-Boot 1.1.4 (Mar 8 2010 - 10:28:58)

AP81 (ar7100) U-boot
DRAM:
sri
32 MB

so it was unsuccessful in flashing the firmware and says Reset Board.
How can I reset the board now, or how can I flash the router via serial interface or with TFTP?

Any advice is highly appreciated
erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 18:30    Post subject: Reply with quote
This was from webinterface when I flashed the original firmware:

System
Flash Firmware
The system is flashing now.
DO NOT POWER OFF THE DEVICE!
Wait a few minutes until you try to reconnect. It might be necessary to renew the address of your computer to reach the device again, depending on your settings.

Starting luci-flash...
Saving config files...
Switching to ramdisk...
Performing system upgrade...
Upgrade completed
Rebooting system...

And it hanged there for a long time so I rebooted the router, and now it is worse than it was.
erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 18:35    Post subject: Reply with quote
And I was unable to get to the "cfe" prompt with Ctrl+C when I was at openwrt and also now. I tried also pressing TPL as I read somewhere but it doesn't send me to cfe prompt
LOM
DD-WRT Guru


Joined: 28 Dec 2008
Posts: 7632

PostPosted: Wed Dec 01, 2010 19:12    Post subject: Reply with quote
erreterr wrote:

How can I reset the board now, or how can I flash the router via serial interface or with TFTP?



You can flash the stock firmware via tftp, the routers ip will be 192.168.1.10 and your computer should be set to a fixed ip of 192.168.1.169.

You have to break into the boot loader before "Autobooting in 1 seconds" by typing tpl in your serial console, which will give you an U-Boot prompt.

The U-Boot command for starting the tftp transfer is Tftpboot.

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erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 22:11    Post subject: Reply with quote
Now I have arrived till this: https://forum.openwrt.org/viewtopic.php?pid=122390#p122390

Thanks for your answers. Do I need to give any flash address? I don't know them. I wanted to flash an original firmware that contains boot file, so I fear of bricking completely the router. And I want to learn.

You know, if I kill the router I will loose my eagerness to learn more from this field.

Thanks
erreterr
DD-WRT Novice


Joined: 15 Oct 2010
Posts: 41

PostPosted: Wed Dec 01, 2010 22:20    Post subject: Reply with quote
It asks me for this file '0A01A8C0.img' as in below output:

Using eth0 device
TFTP from server 192.168.1.169; our IP address is 192.168.1.10
Filename '0A01A8C0.img'.
Load address: 0x0
Loading: T
TFTP error: 'File not found' (1)
Starting again

set link to 100M full by lqm.
*** Warning: no boot file name; using '0A01A8C0.img'
Using eth0 device
TFTP from server 192.168.1.169; our IP address is 192.168.1.10
Filename '0A01A8C0.img'.
Load address: 0x0
Loading: T
TFTP error: 'File not found' (1)
Starting again

set link to 100M full by lqm.

I have put in TFTP directory the original firmware from TP-Link, but I don't know the command to load that file so I just tried this "tftpboot myfilename.bin" but it didn't work. Can I rename my firmware to the name that the router is asking
'0A01A8C0.img'

I renamed the original firmware to the name that U-Boot is asking but I get this output:

*** Warning: no boot file name; using '0A01A8C0.img'
Using eth0 device
TFTP from server 192.168.1.169; our IP address is 192.168.1.10
Filename '0A01A8C0.img'.
Load address: 0x0
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
##############
done
Bytes transferred = 4063744 (3e0200 hex)

Excuse me that I have tired you

Thanks for all your help


erreterr wrote:
Now I have arrived till this: https://forum.openwrt.org/viewtopic.php?pid=122390#p122390

Thanks for your answers. Do I need to give any flash address? I don't know them. I wanted to flash an original firmware that contains boot file, so I fear of bricking completely the router. And I want to learn.

You know, if I kill the router I will loose my eagerness to learn more from this field.

Thanks
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