Subject: Re: Porting NetBSD to Netgear appliances
To: Jonathan A. Kollasch <firstname.lastname@example.org>
From: Jachym Holecek <email@example.com>
Date: 09/14/2005 23:52:15
[Only marginally related and mostly just for the record...]
> On Thursday 25 August 2005 06:35 am, Matthias Scheler wrote:
> > I've not investigated the subject further because:
> > 3.) I'm not sure how well the hardware is suited for a platform bringup.
> > You usually start with an evaluation board which e.g. has a serial
> > port for debug output. I wouldn't be surprised if the units sold by
> > Netgear don't have such things to reduce costs.
> To my knowledge all Netgear WGT634Us have a serial header in them. Many
> similar devices also have unpopulated serial and/or JTAG headers.
JTAG header can only be useful if you're able to get a BSDL model of
the chip (or equivalent -- what matters is 1. IR length 2. BSR register
length and bit description). There is a simple procedure to
detect what devices are present in the chain -- this could be used to
see if you have the right BSDL file. Once you get the file (and docs
on chip's pinout & description of the bus protocols), you can read/write
flash chips and generally toy with all the chips connected to the CPU.
With some more documentation, you can use JTAG to remotely debug your
code (modern -- umm, "non-prehistoric" -- CPUs can do this).
Now, the only problem is that many vendors are not going to provide you
with enough information to use the JTAG (Texas Instruments is particularly
evil ITR). But if you're lucky about docs and want to give this a try --
let me know, I have some JTAG code that could be of use.
-- Jachym Holecek