[PLUG] I hosed my WRT54GL, need JTAG help

[Tim Wescott]

On Thu, September 3, 2009 9:45 am, m0gely wrote:
> Keith Lofstrom wrote:
>> On Wed, Sep 02, 2009 at 02:38:19PM -0700, m0gely wrote:
>>> I don't want to purchase the cable and parts even though they aren't
>>> that expensive. I've flashed many of these and made one silly mistake
>>> on
>>> one doing some experimenting. Is anyone out there capable of providing
>>
>> Can't help you with the cable, but this is the sort of thing I would
>> be willing to kick in part of the cost of.  I could probably build one
>> if I had the time ... which I don't, sigh.
>>
>> And I agree with Russell and others;  there are things you can do
>> without resorting to JTAG.
>
> Well as I mentioned, the Linksys TFTP app indicates nothing no router is
> there to communicate with. I successfully used this app on the router
> when getting rid of the VXWorks OS. So I know how that part works unless
> there are some additional sneaky techniques.
>
> As for the serial idea, are you referring to soldering on a serial port?
> That looks no less invasive than the JTAG approach.
>
> I'm open to idea's, but
>
>> On a side note, which will no doubt hijack the thread:
>>
>> I would strongly suggest doing flashing of WRT's with a better power
>> supply than the wall wart.  I've had good luck with some of the IBM
>> T series AC adapters
>
> Even the newer switching power supplies? The problem with your approach
> is the cost me thinks.
>
Out of curiosity....

Any time I do either the hardware or software design for an embedded board
that needs to be serviced remotely, no matter how much convincing it
takes, I make sure there's a "get out of jail free" mechanism on the
board.  On the hardware side this is a pin to be grounded (or a switch)
whose exclusive function is to let the boot code know that it Absolutely
Positively Should Not attempt to run application code.  Then I make sure
that the boot code checks the pin, and resides in a part of flash that
Never Ever Gets Erased.

Does anyone know if, by chance, the WRT54GL has this, or did they just
rely on JTAG as their download of last resort?  They don't need to be
serviced remotely, and Linksys probably doesn't feel like folks
downloading their own firmware is a big part of their market share, so it
makes oodles of sense for this not to be the case.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

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