void setup() {
  Serial.begin(9600);
  uint64_t data[4]={0,0,0,0};
  uint64_t counter = 0;
  double Value;
  data[0]=0xFFFFF;
   data[1]=0xFFFF;
   data[2]=0xFFFF;
   data[3]=0xFFFA;
   counter = data[3];
      for (int j = 2; j >=0; j--)
      {
        counter = counter | (data[j] << (3 - j) * 16);
      }
    
    Value =  counter * 1.0 / 100;
    Serial.println(str(counter));
    int per=counter%100;

    String a = str(counter/100) ;
    a+= "." + String(per);
    Serial.println(a);
    Serial.println(Value);
}

void loop() {
  // put your main code here, to run repeatedly:

}
char* str( uint64_t num ) {
  static char buf[22];
  char* p = &buf[sizeof(buf)-1];
  *p = '\0';
  do {
    *--p = '0' + (num%10);
    num /= 10;
  } while ( num > 0 );
  return p;
}