AVR-Chat

One quick way that I'm fond of is to write to an external one-byte buffer.
 I usually don't have the I/O lines to do a parallel write, but use a
serial-in, parallel out part.  Before every task spit out a byte that
identifies what task is currently running. If the unit crashes I can look
at what is in that buffer - If one has infinite resources you could put
LEDs on the output so you have a visual indication, if you want to make it
REALLY robust only allow a certain range of values to be written so a
random call of the function won't write garbage out (if your code is OTL.)

Sure, it takes up code and board space though.  If you have a RTC on your
board you could use the static RAM in the part for your storage of the
debug/breadcrumb byte.  But using I2C for this will take a LOT of time and
might not be a great idea.

Just a thought,
DLC

>> So how does one record information to determine where the bug might be
>> in a
>> situation where it is very difficult to reproduce the conditions that
>> caused
>> the software hang?
>>
>> I can have the application leave 'breadcrumbs' at different points but
>> this
>> would either take a lot of time to narrow in on or take a lot of
>> 'breadcrumb' code.
>
>
> I do this for some applications.
> I have a task buffer and an ISR buffer, which are write-only circular
> buffers.
> Any significant task that starts (not one that gets called and decides
> not to run) puts an entry in the task buffer.
> Any ISR that starts puts an entry in the ISR buffer.
>
> On a reset, I can use the ice to breakpoint and read out the buffers.
> In some apps, I've used the serial port to send "last task", "last
> ISR" and "reason for reset" when it's waiting for the boot loader
> magic word.
>
> It all depends on what you need, and how much ram you can spend on it.
>
>
> --
> There is no computer problem which cannot be solved by proper
> application of a sufficiently large hammer.
>
>
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-- 
Dennis Clark
TTT Enterprises