Few questions before I venture into JTAG-land

[RouterDoubter]

Hey folks,

Skip to the end if you don't want to read all this (just to see the questions):
I have an ASUS RT-AC66U (original) that has become bricked. By bricked I mean that it boots but I get the quick flashing power LED (for WPS is processing) and no pingable address. Now the first time this happened, I was able to fix it by using the Asus Firmware Restoration Utility (not in the way you think). The firmware restoration utility didn't work either as after it uploaded the firmware (fully) and after leaving it for 2 hours, I would try local access (nothing), reboot, and the lights returned to the "WPS is processing" mode.

So how did I get it fixed I would put the router in rescue mode (slow flashing light) and initiate an upload of the firmware and stop it mid-way. Somehow this would cause the router to reboot and go back to normal operation. COOL! Doesn't work how anyone ever suggested but this seemed to fix it...for the time being. This is until the Asus firmware restoration could not detect the router in rescue mode. The LED's on the router showed that it was and I could ping the 192 address (even access web GUI rescue mode to clear the NVRAM which did nothing) but my old trick didn't work. Maybe TFTP? Okay so it connects and transferred the firmware successfully but after leaving it for another 2 hours and rebooting, the lights returned to the "WPS is processing" mode (Flashing quickly).

At this point, I read that you, as the dilligent home network engineer that your family prescribed you as, are sick and tired of this sh*t and order an Archer C7 via Prime but a nagging thought in your head says that you're better than this. The IP is pingable in rescue mode! That's got to mean the bootloader is good right? I can access the rescue mode web-GUI right?! I got this f**king $300 router 3 years ago and it sh*ts the bed now!?

No, I'm going to JTAG into this mother and make this right. Worse comes to worse, I have a brand new router.

So for the questions, I've never done JTAG before so treat me as a PCB first-timer:

1. Do I need a special cable to JTAG into the router or would using these and these work (making sure I'm lining up the pins)? Is there a better cable I could use?
2. Will Putty work fine as a JTAG terminal to send the commands? Is there anything you would suggest as an alternative.

 

[TonyH]

Then try TFTP. Make sure your AC adapter is healthy.

 

[RouterDoubter]

Then try TFTP. Make sure your AC adapter is healthy.

> Maybe TFTP? Okay so it connects and transferred the firmware successfully but after leaving it for another 2 hours and rebooting, the lights returned to the "WPS is processing" mode (Flashing quickly).

I did already. It doesn't accept whatever firmware image I try.

 

[Pierino]

Try serial recovery first, as far as I know it isn't supported by jtag. Read this. I have a link in there about the serial cable. I'm Malachi.
https://www.dd-wrt.com/wiki/index.php/Serial_Recovery

 

[Nullity]

Try serial recovery first, as far as I know it isn't supported by jtag. Read this. I have a link in there about the serial cable. I'm Malachi.

There's no link in your post.

 

[Pierino]

There's no link in your post.

My kids are right. I am old. Lol

 

[TonyH]

> Maybe TFTP? Okay so it connects and transferred the firmware successfully but after leaving it for another 2 hours and rebooting, the lights returned to the "WPS is processing" mode (Flashing quickly).

I did already. It doesn't accept whatever firmware image I try.

Try this, power off router >> disconnect everything from router >> wait couple minutes >> Press and hold down reset button >> power up router >> when LED starts blinking let go of reset button. Now anything different? Also when you ping the router what is TTL value? Next to try is as already mentioned serial console.

 

[Nullity]

My kids are right. I am old. Lol

Give it a few years and the mastery of internet markup crappery will be it's own (sad?) degree. Is there a degree for avoiding mistakes?



PS - Don't use children or age as an excuse. I mean, there's really no need for an excuse... though, kids are neato (for you).

 

[KevTech]

So how did I get it fixed I would put the router in rescue mode (slow flashing light) and initiate an upload of the firmware and stop it mid-way.

Ya that is a good way to brick a router!

 

[RouterDoubter]

Ya that is a good way to brick a router!

Not much I could do in the way of getting the router to function. I'd be really curious to see exactly how my method caused it to work as it's been the only thing to kick it out of the mode.

 

[RouterDoubter]

Try serial recovery first, as far as I know it isn't supported by jtag. Read this. I have a link in there about the serial cable. I'm Malachi.
https://www.dd-wrt.com/wiki/index.php/Serial_Recovery

I appreciate the help. I've been perusing that link and looking for a USB to TTL Serial cable. Would this suffice? https://www.amazon.com/dp/B004LBXO2A/?tag=snbforums-20

Does that FTDI chip have level shifting?

Also, I somehow got the router to start working for me and the log is JAMMED with "WPS service starting" errors. Even after getting an updated firmware somehow installed (confirmed via ASUS config page) and wiping the NVRAM via rescue mode, the issue still occurs. I suspect this is what is causing the "WPS is processing" issue.

 

[Pierino]

Not sure about the one you linked to plus it's $20. The one that I posted in the link is cheaper or this one. It's the kind I use. https://www.amazon.com/dp/B009T2ZR6W/?tag=snbforums-20

 

[RouterDoubter]

Not sure about the one you linked to plus it's $20. The one that I posted in the link is cheaper or this one. It's the kind I use. https://www.amazon.com/dp/B009T2ZR6W/?tag=snbforums-20

Alright purchased, received, got the case removed and the serial connected to the properly labelled pins on the PCB. Fired up Putty (saw that the computer recognized the USB to UART Bridge (COM3) in the interim) and set the correct settings. Tried restarting the device and spamming CTRL-C on device startup but no dice. It's just a black putty screen.

Is there anyway to t/s the serial connection? Can I see if the chip is seeing anything?

 

[RouterDoubter]

Well fellas! I made a rookie mistake. I swapped the Tx and the Rx wires on the chip and USB. I should've known that. Got the CFE prompt so WISH ME LUCK!

Spoke too soon. NVRAM ERASE didn't fix the issue. Maybe I could reinstall the bootloader itself or would I need a JTAG port for that? It has to be an issue with the "WPS Processing" error I saw in the logs but I don't know what the next step would be.