Lost Serial Output on Linksys MR7350 (OpenWRT Snapshot) – Need Help with Flashing/Fixing

Installing and Using OpenWrt
1

Hi all,
I was working on my Linksys MR7350 router running OpenWRT Snapshot and encountered an issue. While trying to flash firmware via U-Boot, I lost serial console output after running the following commands:

nand erase 0x0 0x2000000  
nand write 0x44000000 0x0 $filesize

The nand write failed with this error:
NAND write to offset 0 failed -22After rebooting, there’s no serial output anymore.

What I've Tried:

  • Power cycling the device.
  • Testing different baud rates (115200, 57600, 38400).
  • Verified my NodeMCU serial passthrough setup works fine on other devices.
  • Attempted TFTP recovery mode with a static IP (192.168.1.10), but no response.

Could someone guide me on:

  1. How to restore the serial console?
  2. How to properly flash the firmware?

Thanks in advance for your help!

2

Which instructions were you following and what were you trying to achieve? What firmware were you flashing?

1 Like
3

I was trying to flash the snapshot. I was following this https://openwrt.org/inbox/toh/linksys/mr7350_1.0
But there are device specific instructions.
Maybe the boot loader got erased.

4

Nowhere on the page does it say:

Sounds like it, if there is no serial output anymore.

Did you take a backup of the whole nand ever?

5

At this point it's dead, there's nothing (realistically) to recover anymore - it's bricked for good.

6

No. No backup unfortunately.

7

Any way to recover?

8

Apart from buying a new unit and feeding this one to the birds, no.

1 Like
9

Could restore a nand dump from someone else? But I guess the calibration data would be incorrect?

10

Do you have an idea how to 'restore NAND'?

...and yes, the calibration data is another topic (and this irretrievable).

NOR tends to be relatively easy to rewrite externally, NAND is not. Starting with (de-)soldering BGA chips, different NAND types, ECC algorithms and a lot more.

Is it theoretically possible, yes.
Is it realistically possible, no.

Unless you are intimately familiar with low level ARM) snapdragon assembley (JTAG, not to be confused with serial) and are willing to reverse engineer the PCB, to find JTAG pins, alternative NOR headers, pinstrapping, etc., you won't be going anywhere.
This is a case of, "if you have to ask, you won't succeed".

You intentionally drove an industrial strength handheld blender through your routers brains, from brain stem to frontal lobe. Now you're left with the purée, some crayons and a glue stick to fix it, what do you think about your chances?

2 Likes
11

I tried the jtag, but can’t figure out the pin. Don’t think i can do soldering and flash. Don’t think any luck now.

12

Soldering is not my things. I think it’s gone.

1 Like
13

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.