help recovering bricked rt-ac56u

[maurer]

hello community !

As i wanted to join the ARM asuswrt world (i already have an rt-n16 and rt-n66u - mipsel and almost eol) i've bought a bricked rt-ac56u hoping to revive it.

I've connected a serial console and the output is somehow encouraging but I've failed to make any ip connectivity.

What do you suggest I do next?

thanks in advance for any help !

Spoiler: cfe boot log

boot_option=2
Decompressing...decompressLZMA: res=6
done


CFE version 2012.02.18 (r312294) based on BBP 1.0.37 for BCM95301X (32bit,SP,)
Build Date: Tue Jul 3 20:57:05 PDT 2012 (hwnbuild@xl-sj1-04)
Copyright (C) 2000-2008 Broadcom Corporation.

Init Arena
Init Devs.
Boot partition size = 262144(0x40000)
spiflash: found no supported devices
spiflash: found no supported devices
spiflash: found no supported devices
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
CPU type 0x0: 800MHz
Tot mem: 131072 KBytes

CFE mem: 0x00700000 - 0x007B0D68 (724328)
Data: 0x007496FC - 0x00749AD8 (988)
BSS: 0x00749AE8 - 0x0074AD68 (4736)
Heap: 0x0074AD68 - 0x007AED68 (409600)
Stack: 0x007AED68 - 0x007B0D68 (8192)
Text: 0x00700000 - 0x0074114C (266572)

Committing NVRAM...nvram_commit: Failed No valid nvram
done
flash0.0: Device not found
Loader:raw Filesys:tftp Devnull) File:flash0.os: Optionsnull)
Loading: Failed.
Could not load flash0.os:: Network is down
CFE>

 

[RMerlin]

First time I ever see that nvram error message. Try doing an "nvram erase" then rebooting.

 

[RMerlin]

The build date of that CFE looks suspicious BTW. The RT-AC56U was only launched in 2013 (I got a pre-release sample in May 2013 if I recall correctly). Makes me wonder if the previous owner didn't flash an incorrect CFE.

 

[maurer]

thanks for the reply, rmerlin

i also think the previous owner flashed an incorrect CFE
the question now is how can i flash the right CFE ?

 

[Sanna1967]

https://www.snbforums.com/threads/asus-routers-cfe-dumps-collection.17793/

 

[maurer]

Thanks
I only have access to:
CFE>
How do I do it from there?

 

[ColinTaylor]

I don't know whether this is useful or not:

https://www.dd-wrt.com/wiki/index.php/Serial_Recovery#To_flash_the_firmware
https://wiki.openwrt.org/doc/techref/bootloader/cfe#bcm47xx_cfe

 

[maurer]

unfortunately those links weren't much of a help
it seems i cannot set up the ethernet so i can do tftp

Any help is welcomed ! Thanks

some more info below

Spoiler: cfe session logs

CFE> help
Available commands:

et Broadcom Ethernet utility.
show clocks Show current values of the clocks.
nvram NVRAM utility.
reboot Reboot.
flash Update a flash memory device
batch Load a batch file into memory and execute it
go Verify and boot OS image.
boot Load an executable file into memory and execute it
load Load an executable file into memory without executing it
save Save a region of memory to a remote file via TFTP
ping Ping a remote IP host.
arp Display or modify the ARP Table
ifconfig Configure the Ethernet interface
help Obtain help for CFE commands

For more information about a command, enter 'help command-name'
*** command status = 0
CFE> show clocks
Current clocks: 800/400/400/100 Mhz.
*** command status = 0
CFE> nvram show
pmon_ver=CFE 2012.02.18 (r312294)
size: 54 bytes (32714 left)
*** command status = 0
CFE> et -i=eth0 up
*** command status = -6
CFE> ifconfig eth0 -addr=192.168.1.1 -mask=255.255.255.0
Could not activate network interface 'eth0': Error
*** command status = -1
CFE> ping 192.168.1.1
Could not transmit echo request
192.168.1.1 (192.168.1.1): 0 packets sent, 0 received
*** command status = 1

 

[ColinTaylor]

Does "show devices" do anything?

What do you get from just "ifconfig" ?

EDIT: This thread looks to have the most relevant information.

 

[maurer]

output doesn't look good
i've posted the same info on other *WRT forums maybe i can get a hint

CFE> show devices
Invalid command: "devices"
Available "show" commands: clocks

*** command status = -1
CFE> ifconfig
Network interface has not been configured
*** command status = 0

 

[ColinTaylor]

Did you see the comment in this and the other thread from RMerlin saying that you must do a "nvram erase" followed by a "reboot" to get the network interface to work.

 

[maurer]

that was the first thing i've tried

Spoiler: here goes

CFE> nvram erase
*** command status = -6
CFE> reboot
boot_option=2
Decompressing...decompressLZMA: res=6
done


CFE version 2012.02.18 (r312294) based on BBP 1.0.37 for BCM95301X (32bit,SP,)
Build Date: Tue Jul 3 20:57:05 PDT 2012 (hwnbuild@xl-sj1-04)
Copyright (C) 2000-2008 Broadcom Corporation.

Init Arena
Init Devs.
Boot partition size = 262144(0x40000)
spiflash: found no supported devices
spiflash: found no supported devices
spiflash: found no supported devices
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
boot_option=2
otp_size: 0xbc
find_nvram: no nvram found
CPU type 0x0: 800MHz
Tot mem: 131072 KBytes

CFE mem: 0x00700000 - 0x007B0D68 (724328)
Data: 0x007496FC - 0x00749AD8 (988)
BSS: 0x00749AE8 - 0x0074AD68 (4736)
Heap: 0x0074AD68 - 0x007AED68 (409600)
Stack: 0x007AED68 - 0x007B0D68 (8192)
Text: 0x00700000 - 0x0074114C (266572)

Committing NVRAM...nvram_commit: Failed No valid nvram
done
flash0.0: Device not found
Loader:raw Filesys:tftp Devnull) File:flash0.os: Optionsnull)
Loading: Failed.
Could not load flash0.os:: Network is down
CFE>

 

[RMerlin]

I dug up the instructions Asus sent me back in 2013 to flash the RT-AC56U CFE (we were trying to troubleshoot something at the time). Unfortunately the instructions were for TFTP. No idea if it can be done from a USB disk (which might possibly not work either if you can't get the hardware properly configured due to lack of valid nvram).

 

[maurer]

i've googled a little on the subject and it seems cfe can work with usb disks but unfortunately the version i have doesn't seem to recognize usb fat32 or evenfat

 

[RMerlin]

i've googled a little on the subject and it seems cfe can work with usb disks but unfortunately the version i have doesn't seem to recognize usb fat32 or evenfat

Try ext2 just in case.

 

[maurer]

No luck with ext2.
I think I have to give up.
It's frustrating to have serial access and yet be unable to do anything with it considering I already reflashed a device - Zsun wifi card reader - with just uboot access. But then uboot =! CFE

 

[vc1234]

If you consider that a learning project, you may try using the router JTAG interface to reflash CFE. I am not sure if AC56 has an easily identifiable JTAG connector, though:

https://www.snbforums.com/threads/how-to-asus-routers-jtag-recovery.19077/

You'd need a JTAG debugger and a piece of software (e.g. OpenOCD). I use a Segger debugger for similar purposes, but there are much cheaper alternatives.


If it's not a learning project, probably it does not make sense to waste time on it.

 

[RMerlin]

No luck with ext2.
I think I have to give up.
It's frustrating to have serial access and yet be unable to do anything with it considering I already reflashed a device - Zsun wifi card reader - with just uboot access. But then uboot =! CFE

The problem here is that you don't have the correct CFE, therefore half of your hardware isn't getting initialized properly. So for all intents and purposes, it's as if you DON'T have CFE access - it's only half working. Not much else you can do, short of being able to JTAG the correct bootloader on it.

 

[netmind]

I'm trying to unbrick a rt-ac56u router I just got but have a couple of questions before I jump in:

1. Are those pins on the left the serial connectors? There's no labelling and I couldn't confirm.
2. I believe the last owner had dropped merlinwrt RT-AC68U firmware on it. I believe the CFE was swapped. Can I just serial flash the regular stock RT-AC56U firmware? Or do I need to do something different.

Thanks in advance