Re: USB as standard debug interface

On Mar 22, 5:13 am, DaveN <Da...@xxxxxxxxx> wrote:
On 22/03/2011 00:19, rickman wrote:

On Mar 20, 6:52 pm, DaveN<Da...@xxxxxxxxx>  wrote:
On 20/03/2011 17:30, rickman wrote:

It seems to me that you would have to have some sort of protocol for
debugging regardless of using a serial port or a USB VCP.  There are
FTDI devices that directly support a JTAG output which is used in a
number of JTAG adapters for various MCUs.  Is that the sort of thing
you are considering?


I was thinking that the original question was about backdoor debugging..
   To me that means either in the "old" days using an emulator or now
using the JTAG port.  The use of serial over USB, USB direct, ethernet,
CAN or whatever is just a way of communicating with the system.  You may
choose to add data that is useful for debugging but it's not the
"backdoor" method.

All of my debugging is done with JTAG over USB via an FTDI device.
Works pretty well and you can double up a serial port on the same device.


When you use the FTDI JTAG device, what is your target and what
software are you using?  Is this open source software like OpenOCD or
something you rolled yourself?

I'm trying to get someone to add the Freescale Kinetis support to his
tool so I'm looking to understand all the details of what this
requires.  The Kinetis eval boards come with OSJTAG implemented in an
8 bit Freescale MCU.  Or this is also called OSBDM.  I can't seem to
figure out just how difficult it will be to get adequate info to add
support for this through OpenOCD.  It seems like the OSJTAG source
code would have to be reverse engineered to get the interface spec.


Hi Rick,

I'm working with Infineon parts and using the Hitex debugger interface.
  It's a commercial system and also supports ARM devices.  So probably
not a great deal of hep to you.

I think getting to grips with the JTAG interface isn't a trivial task by
any means.  I've noticed that a lot of the the tool vendors offer free
download limited code size versions of the debugger tools, so this may
be help to you, if indeed there is one for your part.


Yes, sure, there are free tools available. I expect to buy an eval
board which will come with a full toolset. But I am looking for
something a bit different and to get there I need to adapt debugging
tools. Someone I know has done this for some of the other CM3
processors and I am encouraging him to lead the way on the Kinetis
parts, partly because I think they are going to be a very good line of
devices and partly because by learning how this is done I can learn
how to make the changes I need. His work is half way there for me, so
it will be about the best starting point I could hope for.

Then there is also the issue that Freescale is representing that their
eval boards offer "Open Source JTAG" and I'm still trying to figure
out if that is really anything worthwhile or if it is just a way for
marketing to make it sound like they are offering hooks into their
debugging process while still keeping it closed for the most part.