Lpc2000

Tom Walsh wrote:

> It's the wigglers. From my experience with them, they can be really
> tempermental.  I found that if I plugged the wiggler directly into the
> printer port, then kept the wire length down to 10 inches, then it
> wasn't too bad.  You have to spend some serious time with an
> oscilloscope fine tuning the electronics of the interface, caps +
> resistors + inductors on the signal lines.  But, they still can be a
> PITA.  The electronics of them is so simple that there isn't any signal
> conditioning of the JTAG signals.

Due to the fact that most controller boards have the JTAG lines to the
outside world without any ESD/EMC protection you may even damage your
board.  I know for sure I damaged some AVR and PIC boards that I had
connected to the PC in this way ...

> IMHO, wigglers are toys that get your feet wet,

Home built wigglers have a fairly good price/quality ratio: Low price and
low quality. For the 'professional' wigglers the ratio gets worse ...

> There seems to be a lot of interest on this list at developing an open
> source wiggler gdb tcp server.  Something to replace the OCDaemon.
> While I find that an intriguing idea with a lot of merit, the weakest
> point is still the wiggler electronics and that of the parallel port
> electronics.

No wiggler type of stuff please.

> What I do think that could be done is an open-source JTAG pod.  Start
> out with something like a Revely RMS101

That's the way to go. I started my lpc21xx development with
http://www.embeddedartists.com/products/boards/lpc2138_100eth.php, a 100
Mbit ethernet board which is now being used to develop a JTAG pod.
Embedded Artists are regularly asking me on my progress - they really love
to create a board with JTAG signalling connection with JTAG software on it
...

> Then using that board, build up an open-source jtag solution.  While
> this would cost more than $10 for the electronics, I feel that it would
> be far superior to a wiggler, but still at a fraction of the cost of a
> commercial JTAG unit?  Software of this caliber would then not be
> limited to just one board electronics, others may decide (maybe
> SparkFun?) to further streamline the electronics and offer it at an even
> lower cost?

Let them all have the fun; Embedded Artists, SparkFun, Olimex - let them
create an (ethernet based) jtag pod that all use the same code-base.

Dominic favors a USB2.0 / FPGA solution. That's just using a different
JTAG interface style and a different front-end to the debugger. These are
not the most difficult parts to do - the nice stuff is in controlling the
Embedded ICE and the attached ARM core.
That't why all these commercial debuggers are so expensive. They need to
support all the different ARM cores and debuggers.

If I have to start a list of requirements for an open source JTAG debugger
this would start with:

* compilable using different GCC installations, not depending on specific OS
* must run on PC targets and embedded (ARM) processors
* support different JTAG back-ends:
  - home built wiggler style interfaces (PC target)
  - USB based FTDI (FT2232) style interface (PC target)
  - USB based microcontroller interface (e.g. lpc2148)
  - Network based microcontroller interface (EmbeddedArtists, SparkFun, ...)
* support different debugger front-ends:
  - GDB stub
  - terminal type command level debugger
  - ARM RDI (Remote Debugger Interface), connects to gdb or commercial.
* Anyone providing hardware for the open source JTAG pod must provide a
  way to perform software update (in case of use of microcontroller)
* license must allow commercial hardware providers to include this software
  (in compiled form) with the hardware, provided that all source code is
  delivered with it.
* license should allow commercial vendors to add specific fron/back-ends
  to allow integration with commercial debuggers or their own
  JTAG hardware
  - must include binary or source for the front/back-end to allow customer
    to rebuild complete program.

Last three bullets is just my mind running away with me ...
I think that by making this open for commercial vendors with their own
hardware or debuggers there is possibly a very large installed base.

Regards,

      Rob