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

[Daniel Golle]

On Mon, Aug 22, 2016 at 10:30:42PM +0200, Jochen Demmer wrote:
> Thank you everybody,
> 
> I've been trying for 2 hours straight to unbrick via serial, using a
> prolific pl2303 adapter but without success.
> 
> I tried screen, picocom and minicom. I tried Apple's terminal emulator and
> iTerm2. Got me a Mac and then Linux. Desperate as I am also connected
> another C7.
> I tried like a whole bunch of different settings but no matter what, I get
> gibberish characters.
> 
> ./picocom /dev/ttyUSB0 -b 115200 -y n -d 8 -p 1
> 
> These are the settings I think they should be set to, but it just won't
> work.
> Actually only RX and TX are connected, because when I connect GND the serial
> connection freezes and let USB subsystem crash. Connecting VCC doesn't seem
> like a good idea, too.

NEVER connect the VCC of the board to a USB-to-serial adapter!

> Any hints?

If connecting the ground causes problems like you described, probably
the device is really far-off the ground-level compared to the GND of
the USB port, so when connected you got a non-neglectible current
flowing and supposedly frying the USB-to-serial dongle. This is often
caused by crappy power supplies, so if you got a laptop, try running
it from battery and have the GND connected, that may fix it.


> 
> Jochen
> 
> On 2016-08-22 11:29, Kevin Darbyshire-Bryant wrote:
> > On 20/08/16 22:35, Jochen Demmer wrote:
> > > Hi,
> > > 
> > > yesterday I bricked an Archer C7 v2 by installing some homebrew
> > > (buildroot) lede firmware.
> > 
> > I've only once encountered an issue which I can only assume was a bad
> > flash.  It's a few months ago so memory is vague.  The serial console
> > was booting linux but it was reporting something about corrupt
> > filesystem markers & couldn't mount filesystems.  Even using the tftp
> > recovery method to re-install factory firmware didn't work...the
> > factory firmware was having similar partition table issues.  I
> > genuinely thought I'd bricked it and purchased a replacement that very
> > morning...with the replacement up & running I then set about seeing
> > what I could do with the borked unit.  Following the 'serial unbrick'
> > instructions at https://wiki.openwrt.org/toh/tp-link/tl-wdr7500 I was
> > able to unbrick it and it's been fine ever since... I'm using it as an
> > additional access point for downstairs in the house, the new one is
> > upstairs.
> > 
> > 
> >        Recovery using serial connection
> > 
> > Connect to your router via serial, power it up, then type "tpl" until
> > the boot process is halted and you should be at the console. Set up a
> > TFTP server with your firmware at 192.168.1.100, then run the
> > following commands (for v2 only):
> > 
> > tftp 0x81000000 [name of your firmware file].bin
> > erase 0x9f020000 +f80000
> > cp.b 0x81000000 0x9f020000 0xf80000
> > reset
> > 
> > 
> > I'm convinced it was the 'erase' command that cleared out some bad
> > data in the flash.  Like I said, the unit has been absolutely rock
> > solid ever since.
> > 
> > Kevin
> > 
> > 
> > 
> > _______________________________________________
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> > Lede-dev at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/lede-dev
> 
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