[NBLUG/talk] JTAG hacking

Mitch Patenaude patenaude at gmail.com
Sat Apr 14 08:19:32 PDT 2012


I haven't done any JTAG hacking myself, but If I recall correctly, that
DB25 cable you're talking about is parallel, not serial, so a DB9 serial
converter won't help you.  I also recall that hardware hackers say that
having a parallel port on the motherboard is invaluable, since the
USB<->Parallel converters don't work in this situation.  If you don't have
a parallel port, just invest in the more expensive USB JTAG device (or
borrow, if you're just going to use it once.)

  -- Mitch

On Fri, Apr 13, 2012 at 10:43 PM, Glenn Kerbein <
glenn at spontaneousdancing.net> wrote:

> Hello,
>
> Let me clarify. I did some more googling around. Apparently the JTAG
> connector turns into a DB25 serial cable. Further discussion with the
> engineer tells me that it is not "genuine" serial communication. I was
> hoping to find a DB25-DB9 converter (I'll scrounge for one, there's gotta
> be one somewhere). From the DB9, I'll feed that into a USB-to-Serial
> converter.
>
> Hopefully I'll be able to use some JTAG-compatible program.
>
> Then, SCIENCE!?
>
> Still kinda at a loss here, and I'd appreciate any help in getting the
> right connectors and software.
>
> Optimally, I wouldn't need to install additional software on there.
>
> Best,
> Glenn
>
>
> On 04/13/2012 09:16 PM, Mark Street wrote:
>
>> Hmmm,
>>
>> I am trying to picture that in my mind.. a huge serial cable. which
>> piece do you need?... I have a JTAG unit that I use with my Globalscale
>> Dreamplug devices, on which I run Debian Wheezy.
>>
>> USB off one end of the JTAG box to the computer and off the other end
>> two small custom cables for the JTAG interface and UART interface of the
>> tiny mobo. My Globalscale devices use UBoot.
>>
>> http://www.**globalscaletechnologies.com/p-**28-guruplug-jtag.aspx<http://www.globalscaletechnologies.com/p-28-guruplug-jtag.aspx>
>>
>>
>>
>> On 4/11/2012 6:45 PM, Glenn Kerbein wrote:
>>
>>> Good day NBLUG,
>>>
>>> I need some assistance with assessing the hardware on an embedded device.
>>>
>>> I have an motherboard that normally runs Linux (a variant of Debian,
>>> but I can't be sure). If they operate normally, you can modify the
>>> BIOS by flashing the SPI (whatever that is). If the device is broken
>>> beyond repair, and the BIOS is to blame, then a new BIOS can be
>>> flashed onto the board using a JTAG connector. I have one half of the
>>> JTAG connector - I just need to figure out how to get the BIOS image
>>> to talk over a huge serial cable.
>>> The issue is that I don't have all the JTAG cabling, etc. to make this
>>> work. I'm waiting on someone else to provide it to me.
>>>
>>> I was Googling around at JTAG. Most people use these connectors to
>>> hack their xboxes. One person figured out how to bridge the serial
>>> JTAG to a serial to female USB port.
>>>
>>> I know someone on this list posted that they have a bunch of xboxes.
>>> Do you have any JTAG connectors for said xboxes?
>>>
>>> I appreciate any input you have!
>>>
>>> Best,
>>> Glenn
>>>
>>
>>
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>
> --
> Living well is the best revenge
>
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