OpenMoko != Neo1973 (Was: Openness (was RE: Concern for usability and ergonomics))

michael at michael at
Wed Jun 13 21:41:34 CEST 2007

JTAG is basically a way to inspect and/or set each and every register on the
processor, not only the registers you're familiar with from a programmer's
point of view, but also registers that might hold the state of input and
output pins, etc. Also since you can control each register and single step the
processor, you can use JTAG to peek and poke to every address or register that
the processor can access on other chips, e.g. RAM. This is slow, of course,
but is very powerful.

It's all on the wiki. I beleive there is a page describing how to download and
set up the debugger. It's standard gdb (for ARM of course) with the
appropriate software (drivers?) for the Neo/USB interface card. I think the
USB port shows up as a serial port. Come to think of it there may be no need
for drivers.

Hopefully this will give you some pointers. If you want to become really
popular, take notes as you go along, and then post them on the wiki as the
start of a JTAG howto. Would be very useful.


On Wed, 13 Jun 2007, Shawn Rutledge wrote:

> Would you post more details about this please?  I have used JTAG for
> programming Atmel micros but am not yet very familiar with how it is
> used for "system exploration" when there are multiple devices on the
> bus.  What is your favorite hardware and software for doing this?
> On 6/12/07, michael at <michael at> wrote:
>>  Good points, Joe and Rod.
>>  To add to this, consider that this device has a JTAG port, and that you
>>  can
>>  buy the necessary interface card and cable for $150, and that the debugger
>>  is
>>  open source.
>>  So even with though the hardware was not promised to be open, we have
>>  tremendous visibility into it.
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