C Function to Convert float to byte array

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Easiest is to make a union:

#include <stdio.h>

int main(void) {
  int ii;
  union {
    float a;
    unsigned char bytes[4];
  } thing;

  thing.a = 1.234;
  for (ii=0; ii<4; ii++) 
    printf ("byte %d is %02x\n", ii, thing.bytes[ii]);
  return 0;
}

Output:

byte 0 is b6
byte 1 is f3
byte 2 is 9d
byte 3 is 3f

Note – there is no guarantee about the byte order… it depends on your machine architecture.

To get your function to work, do this:

void float2Bytes(byte bytes_temp[4],float float_variable){ 
  union {
    float a;
    unsigned char bytes[4];
  } thing;
  thing.a = float_variable;
  memcpy(bytes_temp, thing.bytes, 4);
}

Or to really hack it:

void float2Bytes(byte bytes_temp[4],float float_variable){ 
  memcpy(bytes_temp, (unsigned char*) (&float_variable), 4);
}

Note – in either case I make sure to copy the data to the location given as the input parameter. This is crucial, as local variables will not exist after you return (although you could declare them static, but let’s not teach you bad habits. What if the function gets called again…)

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