Conversion of float to unsigned char

Waqas Ali Khan

Intellectual 570 points

Hello every one,

I am using cc430f5137, i want to convert my float variable into four bytes of character array. Like

float a = 0.135 into hex 0x3E0A3D71

char b[4] ;

now i want to shift this value like that;

char b[0] = 3E
char b[1] = 0A
char b[2] = 3D
char b[3] = 71

i want to know that how i can shift these values like that.

Also i want to ask that if any one know that how float representation in 16 bits can be done.

Thanks

Waqas

over 9 years ago

0 Robert Chen over 9 years ago

Mastermind 9115 points

Method 1:

float a = 0.135;
char b[4];
memcpy(b, a, 4);

Method 2:

float a = 0.135;
char b[4];
*(uint32_t*)b = *(uint32_t*)&a;

Method 3:

union
{
    float f;
    char  c[4];
}float_char_t;

float_char_t a;
a.f = 0.135;
// a.c is what you want as 'b'.
// a.f and a.c use the same memory space.

0 Waqas Ali Khan over 9 years ago in reply to Robert Chen

Intellectual 570 points

for Method 1:
memcpy(b, &a, 4); // need to use & sign
Thanks

0 Robert Chen over 9 years ago in reply to Waqas Ali Khan

Mastermind 9115 points

Yes, thanks for correcting my typo.

0 Ivars K over 9 years ago in reply to Robert Chen

Prodigy 110 points

Hi! I have similar task, but because of my lack of knowledge in these type of codes, can You please dumb down for me 3rd method? Because i'm getting error: variable "float_char_t" is used before its value is set.

0 Robert Chen over 9 years ago in reply to Ivars K

Mastermind 9115 points

Hi,

OK, please post your code snippet.

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Conversion of float to unsigned char