float type format

Projects Programming
15

fnsnoop:
I am outputting the value of the float as hex and I do not understand the last 2 bytes. A1:10:51:C0:0D:0A. It should be just A1:10:51:C0. Maybe this is not right "(char *)&number"?

float number = -3.26664;

void setup() {
 Serial.begin(9600);
}
void loop() {
 Serial.println((char *)&number);
 delay(1000);
}

What you are doing there is called 'type punning' but you're doing it the wrong way. The right way is to use a union:

  union floatUIntUnion {
    float fl;
    uint32_t u32;
    uint8_t u8q[4];
  };
  
  floatUIntUnion fiu;
 
  float flibble=50509.324;
  fiu.fl=flibble;
  Serial.println(fiu.u32,HEX); 
  //Serial.write(fiu.u8q,4); //to write bytes
  
  uint32_t someNumberIEEE754=0x40490FDB;
  fiu.u32=someNumberIEEE754;
  Serial.println(fiu.fl,7);

Google 'C++ union' and 'type punning' to find out more :slight_smile: