Re: USB Boarduino on AVR-Ada Tutorial

[Warren <ve3wwg@gmail.com>]

b.robinson.jp@gmail.com expounded in news:1db702dd-3289-4e76-98fe-
08ab4bae38e1@v8g2000yqe.googlegroups.com:

>>.. I was able to
> compile the project and generate my binary.  The LED stays lit and
> does not flash, but at least I have something to work on now. :)

Check that you have exactly the right part specified for
compiling the unit. What happens is that the object code
may be compatible, but the configured SRAM size is not. This
is critical in the main program, where it initializes the
stack pointer (SP) at startup.

I ran into this when building for atmega328, which supports
a 2K SRAM. I was using an atmega168 with a 1K SRAM instead,
but is otherwise completely compatible with the 328.  

So everything would work until you _called_ something. The
called routine might work (if it needed no local vars or kept
them in registers). But when it would try to return to the
calling program, it would go west. Building for the 328 
sets the SP 1K higher than the 168 address wise, where 
there is no SRAM. So a return would go to address 16#FFFF#,
since FF is what "no memory" returns.

Compiling _libraries_ for a bigger part is ok, since it 
doesn't have to initialize the SP.  But the main program 
has to be "right on" in this respect.

In your case, I suspect that the delay routine is not
returning properly. This strongly hints at the stack 
size problem. So check that MCU= parameter (I had to
get a magnifying glass out to read my chip).

Warren