Hi Brandon!
Yes. My fault was at another place. So this C++ code works. You can use
it only on the PC side. A C code you can find in
$TOSROOT/support/sdk/c/sf/message.c
//--------------------------------------------------------------------------
/* u2f and f2u convert raw 32-bit values to/from float. This code assumes
that the floating point rep in the uint32_t values:
bit 31: sign, bits 30-23: exponent, bits 22-0: mantissa
matches that of a floating point value when such a value is stored in
memory.
*/
/* Note that C99 wants us to use the union approach rather than the
cast-a-pointer approach... */
union f_and_u {
uint32_t u;
float f;
};
static float u2f(uint32_t x)
{
union f_and_u y = { .u = x};
return y.f;
}
static uint32_t f2u(float x)
{
union f_and_u y = { .f = x};
return y.u;
}
//------------------------------------------------------------
The David's implementation should make the conversion superfluous, but
with the one-line patch it doesn't work for me. I assume, one should
really use the cvs version of nesC.
Best wishes,
Andrey
Brandon Fu wrote:
> Hi,
> I have read thru ur emails, and I found out that u mention about int to
> float conversion for the motes packet data. Can I use your methods to
> apply to my application, as I need to convert my int-> float data.
>
> I m using mica2 and mib510, tinyos-2.0. Thank you in advance
>
> yours sincerely,
> brandon
>
>> Date: Tue, 20 Jan 2009 00:04:53 +0100
>> From: andrey.gur...@online.ua
>> To: tinyos-help@millennium.berkeley.edu
>> Subject: [Tinyos-help] Using cast float/int or nx_float
>>
>> Hi all, hi David!
>>
>> I'm trying out two ways of transmitting of float numbers between PC and
>> motes now. The first one is with cast int<->float, the second one is
>> with nx_float (thanks David for this implementation!).
>>
>> The simple C++ example doesn't work for me now:
>> float pi = 1.1;
>> int ipi;
>> assert(sizeof(int) == sizeof(float));
>> ipi = reinterpret_cast<int&>(pi);
>>
>> Motes receive crazy values.
>>
>> Regarding the second approach. David suggests either to download the
>> latest nesc from cvs or to add only one line of code to
>> /usr/bin/nescc-mig. So I've added this one line. But during compiling I
>> receive the message, there are errors nx_float. Without nx_float all is
>> well. I hope you could pointing me, where I'm wrong.
>>
>> And yet another small question. nx_float should work for atmega128 on
>> MicaZ, so it would also work for atmega1281 on IRIS? Or additional
>> changes should be made on platform files for IRIS in order to get it
>> working?
>>
>> Thanks in advance!
>> Andrey
>>
>>
>>
>> > [People regularly ask for nx_float support...]
>> >
>> > I've just added nx_float support to T2 for atmega128 and msp430 based
>> > platforms, along with an apps/tests/NxFloat test app to test that it's
>> > working (works for me on micaz and telosb...).
>> >
>> > The mechanics: each processor arch should define it's functions to
>> > convert floats to and from the wire format for floating point. This
>> > format is defined to be that used by floatToRawIntBits method
>> >
> (http://java.sun.com/javase/6/docs/api/java/lang/Float.html#floatToRawIntBits(float)),
>> > with the resulting 32-bit number in big-endian format.
>> >
>> > Conveniently, on the msp430 and atmega128 we can just use memcpy to do
>> > this conversion ;-)
>> >
>> > It would be good if some people out there would fill out the missing
>> > processors...
>> >
>> > To use this with mig, you will need the latest nesC from CVS, or just
>> > apply the following patch to /usr/bin/nescc-mig:
>> > barnowl:~/motes/nesc/1.3/tools owl$ cvs diff -u -r1.6 nescc-mig.in
>> > Index: nescc-mig.in
>> > ===================================================================
>> > RCS file: /cvsroot/nescc/nesc/tools/nescc-mig.in,v
>> > retrieving revision 1.6
>> > retrieving revision 1.7
>> > diff -u -r1.6 -r1.7
>> > --- nescc-mig.in 2 May 2006 21:56:49 -0000 1.6
>> > +++ nescc-mig.in 19 Sep 2008 23:54:34 -0000 1.7
>> > @@ -185,6 +185,7 @@
>> >
>> > return "PUSH" if $basetype =~ /^AN?[SU]$/;
>> > return "POP" if $basetype eq "AX";
>> > + return "F" if $basetype =~ /^Nnx_float/;
>> > return "U" if $basetype =~ /^Nnxle_u/;
>> > return "I" if $basetype =~ /^Nnxle_/;
>> > return "BU" if $basetype =~ /^Nnx_u/;
>> >
>> >
>> > David
>> > _______________________________________________
>> > Tinyos-devel mailing list
>> > tinyos-de...@millennium.berkeley.edu
>> >
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-devel
>> >
>>
>> _______________________________________________
>> Tinyos-help mailing list
>> Tinyos-help@millennium.berkeley.edu
>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>
> ------------------------------------------------------------------------
> Share your beautiful moments with Photo Gallery. Windows Live Photo
> Gallery <http://get.live.com/photogallery/overview>
_______________________________________________
Tinyos-help mailing list
Tinyos-help@millennium.berkeley.edu
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
