GT-AC5300 bricked router - No keyboard input over serial

Nixer

Occasional Visitor
I've spent countless hours reading the threads here and other places trying to recover my Asus ROG Rapture GT-AC5300.
Router is in boot loop... can't break cfe, I believe that's because my keyboard entries aren't getting passed over serial connection. This is the cable I used to make the serial connection over putty. Initially I tried with RPi 3 serial connection and experienced the same exact behavior
https://www.amazon.com/gp/product/B00QT7LQ88/?tag=snbforums-20

1. Boot loop: When I turn on the route, it goes to boot loop. If I set my PC ip to static 192.168.1.x, I am able to ping the route for ~10 seconds when it's waiting for TFTP server start and then starts timing out when the router reboots. I've attached the log here with name normal.txt. I see these lines in the serial console, but keyboard input doesn't work to interrupt the boot.
External switch id = 5075
*** Press any key to stop auto run (5 seconds) ***
...
Hit ENTER for console...



2. Rescue boot: When I try rescue boot, by holding the reset button and turn on the router, I see the router going to rescue mode with repeated errors messages in the console.. Attached full log rescue-boot.txt. Yes, I am able to ping 192.168.1.1 with 100TTL, no connection issues but can't access CFE in the browser. I am able to use ASUS recovery tool here and upload the firmware... I see the successful upload of firmware in the serial console but at the end of the process, the router gets rebooted and goes into boot loop (1). I also tried using TFTP client (utility, cmd line etc) and the same issue after flashing.


Enable Switch MAC Port Rx/Tx, set PBVLAN to FAN out, set switch to NO-STP.
Loading 255.255.255.255:ASUSSPACELINK ...
TFTP Server
tftpd retry
Loading failed.: CFE error -21
Loading 255.255.255.255:ASUSSPACELINK ...
TFTP Server
tftpd retry
Loading failed.: CFE error -21
Loading 255.255.255.255:ASUSSPACELINK ...
TFTP Server
tftpd retry
Loading failed.: CFE error -21
Loading 255.255.255.255:ASUSSPACELINK ...
TFTP Server


3. CFE/WPS mode??
I also tried to clear NVRAM by holding the WPS button and manually turn on the router... I do get CFE prompt at end but again can't use the keyboard to pass commands. log file wps-cfeboot.txt attached.

External switch id = 5075
Enable Switch MAC Port Rx/Tx, set PBVLAN to FAN out, set switch to NO-STP.
web info: Waiting for connection on socket 0.
CFE>


Here I am able to access the CFE boot over 192.168.1.1. I uploaded different ASUS firmwares downloaded from ASUS support site, but after the reboot it goes back to boot loop (1)

Am I doing something wrong here? The router is out of warranty so can't do RMA with ASUS. Do I need a special adapter for serial connection to use keyboard? Not sure what the difference is between JTAG and UART.
Can someone help?
 

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Nixer

Occasional Visitor
3. CFE/WPS mode??
I also tried to clear NVRAM by holding the WPS button and manually turn on the router... I do get CFE prompt at end but again can't use the keyboard to pass commands. log file wps-cfeboot.txt attached.

External switch id = 5075
Enable Switch MAC Port Rx/Tx, set PBVLAN to FAN out, set switch to NO-STP.
web info: Waiting for connection on socket 0.
CFE>


Here I am able to access the CFE boot over http://192.168.1.1. I was able to successfully flash asus firmware here, but after the reboot it goes back to boot loop (1)

Am I doing something wrong here? The router is out of warranty so can't do RMA with ASUS. Do I need a special adapter for serial connection to use keyboard? Not sure what the difference is between JTAG and UART.
Can someone help?
[/QUOTE]
 

AndreiV

Very Senior Member
1) Never try to upload firmware that is not specific to your model.

2) Have you tried the factory reset button?
 

Nixer

Occasional Visitor
I've only uploaded firmware from asus for this particular model. Never tried any other firmware.
Yes, I tried factory reset....and the normal boot log is after a factory reset
 

Nixer

Occasional Visitor
Yes that's how I connected it. When I connect TtoT and RToR I get no activity in the serial console.
 

Nixer

Occasional Visitor
Also I checked by shorting t and r on the usb to ttl cable and I could see my keyboard entries...so its not the cable.
 

degrub

Very Senior Member
Is it RS-232 or RS-422 (423 ?) on the Pi ?
maybe you need a real serial port on the PC that you are connecting with instead of a USB emulator.
What does the Pi hardware manual state ?

What is the DC power line being used for on the Pi ? i don't recall using that on old RS-232 cables i used to make 50 yrs ago.

here is a link to typical connection

and some issues with usb adapters
 
Last edited:

Nixer

Occasional Visitor
I initially tried with RPi and when that didn't work, I got a USB to serial adapter that I've linked in my original post from Amazon and connected to my pc. I see the same exact behavior in both cases.

I left the 3.3v VCC open. Didn't connect any wires to it. Only GND, TX and RX pins are connected.
 

degrub

Very Senior Member
I recall that some interfaces require the clear to send or other hardware handshake before accepting input. I don’t know about the Pi. If you cannot get the adapter working on a well documented hardware system like the Pi........maybe there is something wrong with the adapter/driver.
 

Nixer

Occasional Visitor
I recall that some interfaces require the clear to send or other hardware handshake before accepting input. I don’t know about the Pi. If you cannot get the adapter working on a well documented hardware system like the Pi........maybe there is something wrong with the adapter/driver.
I am not using the adapter with RPi. I had it connected directly... see the pic attached. I used this this page as reference.

Because it didn't work on RPi, I got an USB to TTL cable and tried it on the PC and that also didn't work.
 

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Nixer

Occasional Visitor
I'm totally stuck and not sure why I can't recover the router. Anyone with experience in dealing with serial console issue like this?
 

AndreiV

Very Senior Member
What happened to cause this router to be bricked?
 

degrub

Very Senior Member
After re-reading your original posts, as a last ditch before pitching the unit, get a real serial port card for your PC, install it, confirm that it is working correctly, make the correct RS232 cable (use all the rs232 pins that are connected to the router board or as default just make a std crossover serial cable using all pins), and see if that gets you access. It really sounds like the router board is expecting a hardware interrupt from the serial port. Either that or the PIC on the board is not responding to interrupts from the serial port.

if you need another identical unit, grab a used one from ebay.
 

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