Help Conversion f32 to HEX

Projects Programming
1

Hi,

I have 2 float32 variables (latitude and longitude) and I need to convert them in Hex.

documentation:
Send a SIGFOX message: AT$SF=XXXXXXXXXXXX (Hexadecimal value)

ex: AT$SF=AA12341F27AA12341F27

actually I have:

    union test {
        float fval;
        int uival;
    } test = { 8.43876f };
    char str [50];
    sprintf(str,"%x",test.uival);
    Serial.print(str);

But it doesn't print the right value

for example

8.43876 -> 41070529 (right output)
529 (arduino output)

can you help me ?
Thanks

2

hex is only a representation. You want to have a string containing the hex value? Little or big endian?

PS, int is just 16-bit on most Arduino's. Try uint32_T.

3

Yes, Little endian.

Can you show me an code-example ?

Thanks

4

Try:

    union test {
        float fval;
        uint32_t uival;
    } test = { 8.43876f };
    char str [50];
    sprintf(str,"%lx",test.uival);
    Serial.print(str);
5

Try this (I don't understand sprintf() well)!

void setup()
{
  Serial.begin(9600);
  union
  {
    float fval;
    long uival;     //int uival;
  } test = { 8.43876f };

  long m = *(long*)&test.fval;
  Serial.println(m, HEX); //shows: 41070529
  Serial.print(test.uival, HEX); //shows: 41070529 
  //char str [50]="";;
  //sprintf(str, "%x", test.uival);
  //Serial.print(str);
}

void loop() 
{

}
6

Thanks !

7

Do note it's not very portable. Both float and long are nor guaranteed to be 32-bit and/or to be the same size. Also, of course, the endianness.

8

Jar0d:
529 (arduino output)

When the OP has mentioned arduino, has he not said about a 'standard Arduino -- UNO/NANO/MEGA'?. If so, float and long are 32 bits. Are not they?