Hi,
I appreciate the answer you gave me.
A. If it has to do with scoping why nesC does not complain for the printf
statement, that has a variable with no assigned value? What instead of a static
variable declaration do a variable declaration inside the readDone? I am kind
of sure that doing the calculations inside the printf("%d",2+3) would work in
todays C compiliers
B. I also looked on the light sensor my telosb has but I could not find
anywhere documented the conversion formula being used over the same video.
Where one can find this conversion formula? I was able to find the temperature
and humidity conversion formulas from the official datasheet of the chip
producer.
I would like to thank you in advance for your help
Regards
Alex
On Monday, October 28, 2013 10:23 AM, Eric Decker <[email protected]> wrote:
On Mon, Oct 28, 2013 at 2:02 AM, Alaios <[email protected]> wrote:
Hi I was looking in the nice tutorial here
>
>http://www.youtube.com/watch?v=x0g4uFr44rk
>
>and I was wondering why at 34:11 we have to declare one more variable for the
>conversion formula to work. I guess this is related to the way tinyos works
>internally.
>
Its not an advanced topic. Rather it is a C variable scoping topic.
it also has nothing with making the conversion formula work.
It does have everything to do with C scoping of variables.
TempRead.readDone is an event that gets signalled by the h/w driver. It is
basically a call out and you have to have some place to put what you compute
from the value the read gives you. The value passed in by the driver (when
calling (signalling) readDone) is call local. its either in registers or on
the stack. Doesn't have a very long lifetime.
So one way is to define a module static, centiGrade. That gets the
computation value.
That is what the tutorial guy is doing by defining the module static
centiGrade. Because it is inside the implementation block of the module its
name will be munged by nesc to make sure it is program unique.
>Can someone shed light on such advanced topic?
>
>R
>Alex
>
>
>
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--
Eric B. Decker
Senior (over 50 :-) Researcher
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