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Topic: TP-Link TL-WR740N stuck in Bootloader Initialisation?!

The content of this topic has been archived on 30 Mar 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

I have slight troubles with the TL-WR740N right now. I flashed OpenWRT on it and it worked flawlessly. SSH and LUCI was working, so everything was okay.

Then, I opened the device and removed the LEDs - I am planing to use the GPIOs for some other stuff - and tried turning on the device again. But the ethernet-ports did not come up. So I checked the serial console, but also there, I did not get much output.

After a second check, I noticed that I must have removed the bootstrapping-resistors that are right next to the LED resistors. So I replaced them all with new 10k-resistors in the right places (the old ones got lost) and booted the router again. Result:

U-Boot 1.1.4 (Mar 22 2013 - 16:16:35)

AP121 (ar9330) U-boot

DRAM:  32 MB
led turning on for 1s...
id read 0x100000ff
flash size 4194304, sector count = 64
Flash:  4 MB
Using default environment

In:    serial
Out:   serial
Err:   serial
Net:   ag7240_enet_initialize...
No valid address in Flash. Using fixed address
No valid address in Flash. Using fixed address
: cfg1 0x5 cfg2 0x7114
eth0: 00:03:7f:09:0b:ad

And that's all the device does. Anybody knows how to fix it? Maybe some of the resistors should not be 10k after all?

i think that a close picture with the resistor you are talking maybe can help others giving you the information of the "stock" configuration...

You're right.

On this picture, the red dots indicate the resistors that were removed but replaced with new 10k ones, the yellowish-white ones mark the led resistors that I replaced with soldering bridges:

http://i.imgur.com/BGMBTTj.jpg?1


And this picture shows the current state:
http://i.imgur.com/v5XQh4j.jpg?1


Also, I tried connecting all the LEDs with their resistors again (on a Breedboard), but that did not help at all. The LEDs all illuminated when the serial said "flashing LEDs for 1 second" though, so I asume that everything is correct there - except maybe some wrong resistor values for the bootstrapping?

Or is it possible that the undefined state affected the Boot-ROM? But how could I reflash the Bootloader then? I don't even see an option for a jtag.

To verify that the flash-content did not get changed with the wrong bootstrapping, I flashed pepes U-Boot-Image into the bootloader-area of the Flash. (I used flashrom for that) It obviously worked, but I still am stuck on the same problem:

*****************************************
*      U-Boot 1.1.4  (Jun 19 2013)      *
*****************************************

AP121 (AR9331) U-Boot for TL-WR74xN/D v4

DRAM:  32 MB
FLASH: Spansion S25FL032P (4 MB)

LED on during eth initialization...

I would take a wild guess and say there is something wrong with the ethernet. I would JTAG this thing, but unfortunately, the JTAG-Pins are pretty hard to access and I'm not sure if that would help all that much anyway.


Edit: And just when I send this, I played a bit with the power-button of the router (pretty fast on-off-on and so on) and all of a sudden, it booted? I guess I have to figure out the right bootstrapping from a second device.

Edit2: However, I cannot get any ethernet connection on the device. Seems like the ethernet is dead in the SoC.

(Last edited by locutus on 2 Aug 2013, 19:46)

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