"HG" <armarm123@hotmail.com> wrote in message
news:47822c89.0405130807.6dc50533@posting.google.com...
> Anyone know of a single wire interface suitable for debugging (+
> ground of course) ?
>
> Is it possible to "compress" JTAG to a single wire ? Are there other
> standards that could be used ? Any vendors (Semi vendors) offer this
> already ?
>
> Thanks in advance,
>
> HGH

For the smaller processors I used to put in a software uart so that I can
send messages  to trace the execution.

Peter


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HG wrote:
> 
> Anyone know of a single wire interface suitable for debugging (+
> ground of course) ?

I don't know if you are referring to two-way communication or one-way.

Someone mentioned the LED output, which is fine if you can take the
time.

One technique I have used is to write some macros that conditionally
call a routine to output a value (byte or other sizes) using pulse width
modulation using skinny and fat pulses for 0 and 1.  I usually drive it
as fast as the processor allows, to minimize timing changes, then sense
it with a digital scope.  My application code looks something like this:

enum {		/* trace events */
  TE_RESET    = 1,	/* reset command received */
  TE_SETCHAN  = 2,      /* set frequency to channel x */
  TE_LOCK     = 3,	/* lock to incoming signal */
  ...
};
...
    TraceEvent (TE_RESET);
...
    TraceEvent (TE_SETCHAN);
    TraceParam (TE_SETCHAN, chan);
...

TraceEvent and TraceParam are macros.  If tracing is disabled, they
generate no code.  If enabled, it calls the PWM routine.  The events can
be individually disabled by setting the symbolic value to 0, which the
macro uses to disable the call as well.

TraceParam is intended on displaying variable information associated
with the preceding TraceEvent.  If the TraceParam first parameter is
zero, the call is omitted, otherwise the value of the second parameter
is sent.  Since the parameter is a constant, it is tested for 0 at
compile time and the trace call code is eliminated if the value is 0. 
There is therefore no overhead for unused trace calls.  With a deep
storage scope, you can get a lot of information in a snapshot, along
with other electrical signals in your system.

I have written similar macros for assembly programs, as well.

Thad

armarm123@hotmail.com (HG) wrote in news:47822c89.0405130807.6dc50533
@posting.google.com:

> Anyone know of a single wire interface suitable for debugging (+
> ground of course) ?
> 
> Is it possible to "compress" JTAG to a single wire ? Are there other
> standards that could be used ? Any vendors (Semi vendors) offer this
> already ?
> 
> Thanks in advance,
> 
> HGH

How about half-duplex RS232? If you don't have a UART available it's not 
too difficult in software - just sample at about 6 to 8 times the baudrate 
and allow for not sampling precisely at the edges of the signal. Of course, 
this can get a bit intrusive for your system timing, but it's doable, I 
seem to remember 9600baud on an 8MHz PIC wasn't too much of a strain - 
sorry, I don't have the code, this was something I was using about ten 
years ago.

Peter.
(posted without apology for cloyingly personal anecdote)

> Anyone know of a single wire interface suitable for debugging (+

LED on a GPIO? Classic debugging interface ;)

On 13 May 2004 09:07:46 -0700, armarm123@hotmail.com (HG) wrote:

>Anyone know of a single wire interface suitable for debugging (+
>ground of course) ?
>
>Is it possible to "compress" JTAG to a single wire ? Are there other
>standards that could be used ? Any vendors (Semi vendors) offer this
>already ?

Atmel has something like that for their newest tinyAVR's:
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3353

-- 
Mikael Ejberg Pedersen

HG schrieb:

> Anyone know of a single wire interface suitable for debugging (+
> ground of course) ?
> 
> Is it possible to "compress" JTAG to a single wire ? Are there other
> standards that could be used ? Any vendors (Semi vendors) offer this
> already ?

Look at the Dallas 1-wire-protocol. As bidirectional protocol
it should also be useful for debugging.
Slooow however if you need to transfer more than a few bytes.

-- 
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Ma�.
http://www.autometer.de

Anyone know of a single wire interface suitable for debugging (+
ground of course) ?

Is it possible to "compress" JTAG to a single wire ? Are there other
standards that could be used ? Any vendors (Semi vendors) offer this
already ?

Thanks in advance,

HGH