AVR-Chat

At 09:01 PM 30/01/2007, you wrote:
>It sounds to me as though you're saying that you _can_ program through
>DW -

You CANNOT program the fuses through DW but Flash and EEPROM get
programmed (or reprogrammed) automatically every time you enter
a debug session or do a "build and run". ie you don't get the
usual programming screen but the SUCCESSFULLY assembled or compiled
hex and eep files just get dumped into the target chip.

In other words DW is NOT intended as a general purpose programmer as
you could use JTAG or ISP but there is no need to go into ISP,
program the chip, enable DW, start a debug session, find a bug,
exit DW, fix the bug and restart allover again as some people
seem to do.

>"AVR devices with debugWIRE interface are shipped with the DWEN fuse
>un-programmed from the factory. The debugWIRE interface itself cannot
>enable this fuse."

This may refer to the DW setup of V+, GND and RESET pins only
on which DW runs. If you just plug the usual 6 way ISP connector
into your target, Studio will switch between ISP (all 6 pins needed)
and DW (only 3 pins needed) as required.

Try this out.

With a new chip or a chip that has DW disabled.
   Enter ISP mode and program the fuses (EXCEPT DW) as required
   ie clock and BOD fuse. Leave the 6 way ISP cable in place.

   Go into a DW project, if you have already successfully generated
   both the .hex and eep files (if used) go into debug> start debugging.
   A window will appear prompting you to either retry DW (as it can't connect
   because DW is off at the moment) or enable DW though ISP. Select the latter.
   DW gets enable via ISP (remember that it's already connected above).
   FOLLOW THE DIRECTIONS about cycling the target power.

   You are now into DW mode, your code will be automatically dumped 
into the chip
   and the cursor will go the reset vector. You are now ready to either run,
   single step or whatever.

   If and when you find any bugs, fix them and do a "build and run", 
your code will
   be automatically dumped into the chip and the cursor will go the 
reset vector as
   above. If you find lots of errors it may be wise just to do a build untill
   successful and then do a "build and run".

   NEVER EXIT DW untill your code is completely debugged and you want 
to put the board
   into field use. If this is a workshop board used for debugging 
purpose you can leave
   DW enabled at all times.

   NOTE: The above is based on the Dragon but I suspect the JTAG mk2 
will work the same
   as far as DW is concerned. The Miso, Mosi and CLK lines are not 
used in DW mode but
   I found some loading on those lines, so if you use any of those 
pins for input you
   may want to make a 3 wire "octopus" DW lead to completely free up 
those 3 pins.
   I think that the JTAG mk2 already comes with "octopus" leads.




Regards

John Samperi

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