bricked buffalo wzr-1750DHP (eu-jp?)

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pitfermi
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PostPosted: Mon Jun 07, 2021 23:10    Post subject: Re: bricked buffalo wzr-1750DHP (eu-jp?) Reply with quote
tedm wrote:
pitfermi wrote:
tried to tftp a dd wrt firmware and then a buffalo stock firmware. it was transfered ok, but i got error code -4 I/O, then tried erasing nvram,


OK hold on here.

How do you know the CFE is not working? This is not a PC - if the CFE detects what it thinks is a valid firmware image it transfers CPU control to that image in less than a second. You maybe have a half-second window where you have to bang madly on Cntl-C or whatever escape character to break the boot and get the CFE prompt.

If the CFE thinks the image is good but the image is scotched then the moment the device powers up and the CFE transfers control the CPU will hit the corrupted image and either end up in a tight loop or crash. It's only if the CFE thinks the image is scotched will it decide as a last ditch effort to issue a prompt at the serial port.

The I/O error you got COULD have been because your AC adapter was putting out too low voltage and so the CPU was crashing during normal code execution. If you get an I/O error from the CFE during a transfer then you have to stop what you are doing and fix that first. Either you have bad power or part of the flash chip itself has failed or your ethernet connection to the device is messed up.

Please post the sequence of events and things that you did to erase the nvram.


i posted my sequence of actions in a post above.
i keep ctrl+C pressed while turning the device on, while already having putty opened and running on the COM3 port where the usb uart is located.
the split second that i hit the power button, it outputs some unown characters on the terminal@, like so
▒▒▒▒▒▒▒ ▒▒▒
since i dont know in depth how the boot sequence works, your point might be the solution here. cfe might still work, but as i said, i hold down ctrl C while turning device on, but it doesnt go into CFE. so no, im not worried that i skip the part where it checks by banging the key combination
the ac power adapter, 12V is fine, i checked. also had another similar adapter that i tried, also 12V, 5A. so the power is not the issue. hope that helps for the further troubleshooting?
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kernel-panic69
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PostPosted: Tue Jun 08, 2021 0:47    Post subject: Reply with quote
Check your connections, especially your ground, also make sure that
Code:
Window > Translation > "Enable VT100 line drawing even in UTF-8 mode".

is set. REF: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=323931

And here I thought you completely wiped your flash chip... you got lucky. You should be able to serial flash it PROPERLY once you've fixed output.

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pitfermi
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PostPosted: Tue Jun 08, 2021 3:17    Post subject: Reply with quote
kernel-panic69 wrote:
Check your connections, especially your ground, also make sure that
Code:
Window > Translation > "Enable VT100 line drawing even in UTF-8 mode".

is set. REF: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=323931

And here I thought you completely wiped your flash chip... you got lucky. You should be able to serial flash it PROPERLY once you've fixed output.


i changed the vt100 enable thing. it did not make a difference. connections are fine. usb adapter also works fine.
check video below to see what im getting in putty as output.
this output is acquired when the usb adapter tx pin is connected to the tx pin of the board, according to the pinout reference that other people here posted for this router.
when i managed to go into cfe, i used my own pinout which is exactly opposite, but as i said, using my own pinout i get no output on putty
https://www.youtube.com/watch?v=udHs3p6KUj8

so to be clear. using the exact same configuration before and after the CFE access, the router uart interface does not output anything this time. only if i swap tx and rx it is that i get what is presented in the video.
check this as well.
https://kdpeter.blogspot.com/2015/04/adding-serial-console-to-buffalo-air.html?m=1
kernel-panic69
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PostPosted: Tue Jun 08, 2021 4:35    Post subject: Reply with quote
Tx on router goes to Rx on USB adapter; Rx on router goes to Tx on USB adapter; GND to GND, no Vcc connection, whatsoever. Must be good solid connections. There is a bad connection, broken wire, or a wire is in the wrong place.
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pitfermi
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PostPosted: Tue Jun 08, 2021 8:36    Post subject: Reply with quote
kernel-panic69 wrote:
Tx on router goes to Rx on USB adapter; Rx on router goes to Tx on USB adapter; GND to GND, no Vcc connection, whatsoever. Must be good solid connections. There is a bad connection, broken wire, or a wire is in the wrong place.


yep. still no luck. also buffalo support does not want to provide any pinouts, since i flashed a third party firmware. funny, since they sell a version of this router with dd wrt preflashed...
pitfermi
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PostPosted: Tue Jun 08, 2021 19:55    Post subject: Reply with quote
just a little update and something that i forgot to mention.

firstly, I verified once again that the usb-uart adapter works as it should, by debugging an old wrt54gl router.
Entering show devices command in CFE, I recalled that almost the same device list appeared when debugging the buffalo router. check attached picture.




secondly, before getting access to the CFE, i tried hooking up another usb-uart adapter, similar to the one i am using now, which uses 5V logic on the RX/TX pins. seeing that i could not get it to work(weird character output on both configs, rx/rx, rx/tx),I remembered it is 5V logic, so i tried the 3.3V one, which then gave me access to CFE, where I then did what I mentioned in previous posts. That being said, i was lucky that the pins of the router were 5V tolerant(probably up to 5.5V) and did not damage the serial interface or at least that's what I believe, since it worked with the 3.3V adapter afterwards.



I don't know where the second uart is located on the buffalo pcb. Could it help me acess CFE, or is that uart reserved for another purpose? again, i dont think the main uart that worked for me was fried when hooking the 5V logic usb adapter, but I thought I should mention it regardless.
Any help as to how to proceed is appreciated



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pitfermi
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PostPosted: Wed Jun 09, 2021 10:55    Post subject: Reply with quote
in case following info helps.
Firmware files that I recall flashing using CFE/TFTP(Tftpd64):
-wzr_1750dhp_ap_227 (oem firmware from buffalo.jp website)
-wzr1750dhpd-v24sp2-23709c.bin
-wzr1750dhpd-v24sp2-23709c_recover.enc
all of them were transferred to the router/client, but i got error code -4. something with I/O being incorrect. dont remember sadly and yes, i should have made screenshots i know.. BUT, i am almost certain, that the last one(.enc extension) was the one that bricked/wiped the bootloader.

by the way. i do have access to a 4channel oscilloscope and checked the uart interface, it yields no output
pitfermi
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PostPosted: Wed Jun 16, 2021 19:48    Post subject: Reply with quote
Original post updated with more/detailed info on what I did in the process. in case it helps determine what happened and/or if the bootloader is still intact?
pitfermi
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PostPosted: Tue Jun 28, 2022 0:40    Post subject: Still not solved Reply with quote
Hi again, after a year, lol. I finally got around to flashing the new bootloader with a tsop48 adapter. i removed the zentel memory and placed it in the adapter. i started at memory location 0x0 and used the file from this thread: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=329374
i verified the flash and there were no errors. i soldered the flash back on the board.

i tried reading the serial with a usb uart adapter but all i get is a bunch of zeroes inside brackets [00] and some [02]'s too in the serial terminal, @ 115200 baud.
what can I do now?
dale_gribble39
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PostPosted: Tue Jun 28, 2022 1:30    Post subject: Reply with quote
I think 1MB is a little large for a Broadcom CFE bootloader file; I examined it and it looked like it had nvram information in it...
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pitfermi
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Joined: 06 Jun 2021
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PostPosted: Tue Jun 28, 2022 1:41    Post subject: Reply with quote
dale_gribble39 wrote:
I think 1MB is a little large for a Broadcom CFE bootloader file; I examined it and it looked like it had nvram information in it...


Nooooooooooooo Sad((
If i flash the correct bootloader starting at 0x00, should it work, or do i have to take any additional steps? I was told the cfe file was the proper one.

On another note, i think i have found jtag pinout..check attachmemts..



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dale_gribble39
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PostPosted: Tue Jun 28, 2022 13:53    Post subject: Reply with quote
Your Buffalo is not a MIPS device, but those may be the same. Only one way to find out for sure. Most of the Broadcom Northstar units supported by DD-WRT have a vendor-installed 512kb CFE bootloader. The only way it would be 1024MB is if it includes the Buffalo-supplied custom bootloader that is present in all Northstar builds by default.
_________________
"The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep." - Robert Frost

"I am one of the noticeable ones - notice me" - Dale Frances McKenzie Bozzio

<fact>code knows no gender</fact>

This is me, knowing I've ruffled your feathers, and not giving a ****
Some people are still hard-headed.

--------------------------------------
Mac Pro (Mid 2012) - Two 2.4GHz 6-Core Intel Xeon E5645 processors 64GB 1333MHz DDR3 ECC SDRAM OpenSUSE Leap 15.5
pitfermi
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PostPosted: Tue Jun 28, 2022 20:03    Post subject: Reply with quote
just a screenshot from the serial i am getting when powering up the thing, after flashing the cfe from another post https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=329374
.

it seems that there is new content on the flash, but it is might be not the one I need...



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