[avr-gcc-list] Re: AVR-GCC-list Digest, Vol 25, Issue 16

[Steve Franks]

> From: Reza Naima <address@hidden>
> Subject: [avr-gcc-list] very strange stuff... possessed circuit?
> To: address@hidden
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> I've been working on a project, all was going as expected, then
> everything started behaving strange.  I'll spare the history and get to
> the details.
>
> I can write a simple application but it will not run - power cycling it
> or doing whatever I can to it.  I've got status leds attached to F0, F1,
> and F2 and F1 and F2 are held high.  If i use the JTAG bebugger and
> ender debug mode, it works fine.  If I unplug it after entering debug
> mode, it works fine.  If I power cycle it after that point, it works
> fine.  It seems that it's getting stuck at some point and that the
> debugger gets it unstuck.
>
> This happened on an ATMEGA64.  I swapped it out with an ATMEGA128 with
> the same results.  All the fuses look fine -- otherwise, I have no idea
> what's causing this.  The thing is that it worked fine for the longest
> time, then this started up.  Any thoughts?  Is it possessed?
>
> thanks,
> Reza

The Jtag-Ice2 holds the device in reset most all of the time when it's
connected - it's quite annoying.  I've not bothered to flowchart
precise operation, but after connecting to it with avrstudio, you'll
find it pretty much keeps your part in reset unless you tell it to
debug.  I've make up quite a few pass-thru connectors with the reset
pin cut out myself, since you don't need the reset pin for programming
with the jtag ice.  You might try "avrdude" instead of avrstudio for
programming, it may well not instruct the jtagice to hold onto the
reset line - haven't tried it - been on a project for the last few
months with no jtag pins and use an avrisp for all our programming.

I do know for certain, that the avrisp, even though it uses the reset
pin for programming, always lets go of it after a program cycle.  I
guess this is due to an assumption at atmel about what it is you are
intending to do if you have an avrisp hooked up vs. a jtagice (burn
vs. debug).

Steve