Le 07/01/2012 14:09, David Brown a écrit :
> On 06/01/12 20:30, Grant Edwards wrote:
>> On 2012-01-06, steve ayer<a...@handhelds.org> wrote:
>>
>>> of course, you could put a wire on an unused gpio pin and put the
>>> device on a scope; that will give you accurate timing of code
>>> segments.
>>
>> In my experience that's usually the easiest method by far...
>>
>
> One thing to watch out for here is that when you write something like:
>
> ...
> setPinHi();
> test code ...
> setPinLo();
> ...
>
> you might not be timing all of the test code, or only the test code.
> The compiler can often move the code around the "setPin" statements,
> especially if they are macros or functions that the compiler can see
> during the compilation.
Hmm, if they are functions they should be sequence points, and thus
should be kept in sequence. For macros of course, it would depend on
what they expand to.
In any case, one can always force sequence points /memory barriers.
Don't know how they'd look like for MSP430 gcc, but for ARM gcc that
would be "asm volatile ("" : : : "memory");"
Amicalement,
--
Albert.
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