[ECOS] Question for displaying floating point in eCOS aplication. Thanks a lot

[Andrew Lunn]

On Thu, Aug 07, 2003 at 01:43:58PM +0100, QiangHuang wrote:
> Hi all:
>    I tried to use fprintf() to display a floating point value but seems it
> is real*8 format. is this right? my data is in real*4 format so what flag
> should I use to display floating point (real*4 format) data with fprintf()?
> 
> for example
> 
> 
> // data in real*8 format = 4
> cyg_uint32 real8_data = 0x4010 0000;
> 
> // data in real*4 format = 4
> cyg_uint32 real4_data = 0x4080 0000;
> 
> fprintf(client, "%f ", real8_data);
> // I can see the output is: 4 -- correct
> 
> fprintf(client, "%f ", real4_data);
> // I can see the output is:  512 -- not correct
> 
> Did I make anything wrong here?
> can anybody help on this? Thanks a lot.

Approaching the problem from the other end:

int main(int argc, char * argv[]) 
{
  float f = 4.0;
  double d = 4.0;
  
  printf("f=%f, 0x%x\n",f,*(unsigned long *)&f);
  printf("d=%f, 0x%llx\n",f,*(unsigned long long *)&d);
  
  return 0;
}

./float
f=4.000000, 0x40800000
d=4.000000, 0x4010000000000000

I was talking nonsense about normalization. I should go back and read
the CompSci text book.

You problems might be types and casting. Notice how i cast my
float/double before printing them. If your real8_data truly is a
cyg_uint32, the compiler will silently convert it to a double before
printing it. Although i would not expect 512!

         Andrew

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