TEW-812DRU v2 Bricked after power loss

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DatPratt
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Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Tue Mar 08, 2016 1:01    Post subject: TEW-812DRU v2 Bricked after power loss Reply with quote
Hi all,

Trendnet TEW-812DRU v2 running v24-sp2 build 24160

I dont really have any idea why this happened...simply unplugged the router one day because I had to, left it in the same place for a week, I come back and plug it in...no wireless. Everything was working perfectly before, even with soft reboots which I had regularly scheduled.

I let it go when I first noticed, but the next day I got it out from where it usually is and try direct ethernet connection and nothing (says identifying the whole time).

Despite having the reset button disabled (probably this would be an easy fix if I decided to not do that), I understand that a hard 30/30/30 reset still works when holding the button in the whole time, even while plugging it in again. All this has allowed me to do is change the lights that come on when it has power.

Light order is Power, WAN, LANs, 2.4 GHz, 5 GHz, and USB. Power light has been green and solid for this whole process whenever I try anything...not sure if power light can even tell me anything (like on some routers where it would be orange or blinking).

When I leave it powered off for a longer amount of time before powering on I get power, and the wireless indicators, and USB, but with no actual wireless network. After a hard reset I only get Power and USB lights. If i leave it for a while i can get those 4 lights again and repeat that whole process with no other apparent changes other than those lights.

Things I have tried include:

In both of these states I have tried physical ethernet connection and the only thing I get is nothing, but for some reason one time I got some connection with the title of the STOCK SSID, not ddwrt...so I am not sure if ddwrt is still on it even...and I lost that connection and probably would not be able to ping to it or go to http://tew-812dru anyway...not sure if I can replicate that situation again or not...i think it happened when the ethernet was plugged in when I powered on but it has not happened again by doing that, only happened once.

with ethernet connection: ping -t -w 2 192.168.10.1 and normal ping 192.168.10.1. With that the only sign of hope is that sometimes I get "Destination net unreachable". I think it only happens when I set the ethernet connection to a static IP of 192.168.10.1 with the subnet mask. But apparently that means the subnet is wrong as I read somewhere...

I have even opened it up and looked around for physical problems, and found none. Also I dont think there is a JTAG connection on this board, but I think there is a 4 pin serial next to the reset button. Although I have never done any of that and dont have the equipment for it right now anyway...

However there is a set of pins exactly like the ones in this post...
https://www.dd-wrt.com/phpBB2/viewtopic.php?p=502580
and I was considering trying that, but did not yet and not sure how safe it is.

What else can I try? or maybe is there any of this I have been doing wrong?
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Malachi
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Joined: 17 Jul 2012
Posts: 7113
Location: Columbus, Ohio

PostPosted: Tue Mar 08, 2016 2:28    Post subject: Reply with quote
Don't pin short it and if you disabled the reset button it doesn't work. That's why you shouldn't reset it.
You'll have to try serial recovery.

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DatPratt
DD-WRT Novice


Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Tue Mar 08, 2016 6:01    Post subject: Reply with quote
So how do I know that these 4 pins next to the red reset button (which sticks out to the right) are the serial connection? Or is it actually the other set of 4 on the lower left of the image?

Do I need to get all of the solder out of them? because they are only half filled with solder...

how do I make them into pins? I have to buy a pin header or something like that?

I was looking at this connector, would get it if I am sure enough that I could get it all to work.
http://www.newark.com/adafruit-industries/954/usb-to-ttl-serial-cable-raspberry/dp/44W3509

Here is an image, the 4 pins I am looking at are between the 16 pin array and the large cylinder capacitor and next to the red reset button, all being along the right side of the board.

https://www.dropbox.com/s/ikpnbwebrctug1h/img_20160307_235524_2_179.jpg?dl=0

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Last edited by DatPratt on Wed Mar 23, 2016 21:04; edited 2 times in total
DatPratt
DD-WRT Novice


Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Tue Mar 08, 2016 20:36    Post subject: Reply with quote
Malachi wrote:
Don't pin short it and if you disabled the reset button it doesn't work. That's why you shouldn't reset it.
You'll have to try serial recovery.


Is there anything else I can try before doing physical things on the board?
DatPratt
DD-WRT Novice


Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Tue Mar 22, 2016 4:23    Post subject: TEW-812DRU v2 Bricked after power loss - Update Reply with quote
Update:

So I have got a connection to it with serial via putty.

But all I get in the display is
Code:
Decompressing...error 1


Also I have been using this post more to talk about the problem
https://www.dd-wrt.com/phpBB2/viewtopic.php?t=175052&postdays=0&postorder=asc&start=30

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LOM
DD-WRT Guru


Joined: 28 Dec 2008
Posts: 7628

PostPosted: Wed Mar 23, 2016 5:36    Post subject: Re: TEW-812DRU v2 Bricked after power loss - Update Reply with quote
DatPratt wrote:
Update:

So I have got a connection to it with serial via putty.

But all I get in the display is
Code:
Decompressing...error 1




The error means that the CFE can not be decompressed for running in ram, most likely because the CFE is corrupted or because ram is bad. It could also be due to wrong cpu clock frequency.
Your CFE is not running after this so tftp reflash is not possible.

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Kernel panic: Aiee, killing interrupt handler!
DatPratt
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Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Wed Mar 23, 2016 5:41    Post subject: Re: TEW-812DRU v2 Bricked after power loss - Update Reply with quote
LOM wrote:
DatPratt wrote:
Update:

So I have got a connection to it with serial via putty.

But all I get in the display is
Code:
Decompressing...error 1




The error means that the CFE can not be decompressed for running in ram, most likely because the CFE is corrupted or because ram is bad. It could also be due to wrong cpu clock frequency.
Your CFE is not running after this so tftp reflash is not possible.


Yeah...I was thinking that there was no way to reflash or erase nvram now at least through the CFE anyway...

Still, I am curious of the origin of the problem. It does not make sense that the ram just goes bad. And I am pretty sure that nothing I have done directly has corrupted the CFE especially since i have not had any bad flashes. I also have not under or overclocked.

What actually causes CFE to become corrupted?

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LOM
DD-WRT Guru


Joined: 28 Dec 2008
Posts: 7628

PostPosted: Wed Mar 23, 2016 10:26    Post subject: Re: TEW-812DRU v2 Bricked after power loss - Update Reply with quote
DatPratt wrote:


What actually causes CFE to become corrupted?


A single bit error in the flash is enough for the decompress routine (lzma) to fail.
Stuck bits in a flash is a manufacturing defect which can appear after month of use.

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Kernel panic: Aiee, killing interrupt handler!
DatPratt
DD-WRT Novice


Joined: 18 Jul 2015
Posts: 21
Location: Ohio

PostPosted: Wed Mar 23, 2016 21:02    Post subject: Reply with quote
Since I was attempting to use the reset button even though I have disabled it...Could that have caused any problem with the CFE?

Also, is it be possible to replace the CFE along a serial connection with...let's say U-Boot?

This particular case has me very curious about some possibility other than just trying to find a way to get rid of this device...although I may just end up donating it unless it is TRULY useless and broken...

https://github.com/Chadster766/McWRT/wiki/WRT1900AC-corrupt-bootloader-recovery

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