[LEDE-DEV] Fwd: TP-Link Archer C7 boot loop

[Jon]

Thought I'd report back.   I found out why I wasn't able to get console 
with the serial
adapter.  Long story short,  it seems the TX line of my Archer C6 v2 has 
something like
500 ohms impedance to ground and to VCC!  Very strange.

The RX measures about 10K both to gnd and VCC,  like you'd expect. 
Adding a 10K pull
up won't get the TX high enough to work,  adding a 1k won't either, you 
have to go a bit
lower than that.  An 820 ohm did the trick.  I thought I had a bad 
serial adapter, chased
that for a while.  Even bought another C7,  a v3,  thinking the first 
was really unrecoverable,
and that one needed a pull up as well,  but a 20K was enough pull up to 
work fine.

I have no idea why that particular C7 has such low value pullups, on TX 
only...  But, I now
have got the console, done the manual TFTP, erase, and load,  and yea 
verily... it frikin' works now.

I didn't learn much about WHY loading the custom FW build caused it to 
get stuck, the same FW
has since loaded and run.   I did use pins stuck in the holes, no 
soldered  header on the port
the first time, so possibly there was a break in connection and the FW 
load was corrupted.

Wanted to pass this along,  for those who might have a similar problem 
of not being able
to get into the console with the serial adapter.  Measure from the 
signal pin to 3.3V and
ground with an ohmmeter,  if it's below 1K, you need to grab a lower 
value pull up.

>    Hello all,  am having a similar problem with a boot loop.  After an
> attempted flash of a LEDE build,  my router is in a 5-6 second loop.
>
> Am 20.08.2016 um 23:35 schrieb Jochen Demmer:
> >//>/> yesterday I bricked an Archer C7 v2 by installing some homebrew />/(buildroot) lede firmware. > It got stuck in a boot loop and it's also />/not reachable on 192.168.1.1 on any time during > boot whatsoever. No />/failsafe mode. Archer C7 v2 can be un-brick with TFTP and U-Boot of />/the router. If you try it with the serial console, you need a program />/which hits 'tpl' for you. > I don't know how to debug this. Could />/someone give me a hint? Is maybe something wrong > within lede for />/Archer C7 ? Did you connect a UART adapter to the router? My Lede />/build for Archer C7 v2 works perfectly. I did never use the />/pre-compiled images and I'm using sysupgrade images only. Regards, 
> Hartmut /   I've progressed thru successful serial terminal configuration, and am
> observing the loop,  as well as the TFTP firmware loads attemps.
> I seem to be failing a check of product ID and version.  Then, the
> router attempts to boot the firmware with the same failure that I see in
> the regular boot loop:
>
> >/#Example of firmware TFTP load, and subsequent problem leading to reboot />//>/dup 1 speed 1000 />/Using eth1 device />/TFTP from server 192.168.0.66; our IP address is 192.168.0.86 />/Filename 'ArcherC7v2_tp_recovery.bin'. />/Load address: 0x80060000 />/Loading: T />/################################################################# />/####################### /editing out hashtags
> >/################################################################# />/################################################################# />/####################################################### />/done />/Bytes transferred = 16252928 (f80000 hex) />/original_product_id = ffffffff />/original_product_ver = ffffffff />/recovery_product_id = c7000002 />/recovery_product_ver = 01 />/auto update firmware: product id verify fail! />/Autobooting in 1 seconds />/## Booting image at 9f020000 ... />/Uncompressing Kernel Image ... Stream with EOS marker is not />/supportedLZMA ERROR 1 - must RESET board to recover />//>/U-Boot 1.1.4 (Oct 14 2015 - 13:34:14) /
> The last part starting at the "Autobooting in 1 seconds",  is the end of
> the boot loop,  where it complains,  then U-Boot starts again. The
> regular loop is much longer,  culminating in the image boot and the same
> error.
>
> My problem is,  I can't seem to catch it with tpl,   to stop it and get
> to console.   Have seen another method of erasing and writing from the
> console, but either I need to type faster,  or something's wrong with my
> console config.  Are there any other ways to stop a boot and go to console?
>
> Thanks...
>
> Jon