Extract number form a hexadecimal dataFrame parseInt()ParseFloat()

Question

Im trying to parse the data coming from some sensors, The data I recive is a hexadecimal number f.e.: '450934644ad7a38441' I want to extract the last 8 characters, that are the value for temperature taken, and transform it into a readable number. I tried this website: https://www.scadacore.com/tools/programming-calculators/online-hex-converter/

Here when you input d7a38441 it is processed and the wanted number is under Float - Little Endian (DCBA) system. Also the conversion it`s doing is under UINT32 - Big Endian (ABCD) system

How do I convert this number into float? I Tried reading some other questions here but couldnt find a solution. parseFloat() gives me NaN.

I would appreciate some light.

var data = '450934644ad7a38441';

function main(data) {

  var result = [
    {      
        "key": "temperature",
        "value": parseInt('0x'+data.substring(10))
    }
    ]
  
  
  return result;
}

console.log(main(data));
// expected output: Array [Object { key: "temperature", value: 16.58 }]

Answer 1

I think this is what you need. String received by function yourStringToFloat is your data variable received by main function in your example. Of course you can fix precision according to your needs.

function flipHexString(hexValue, hexDigits) {
  var h = hexValue.substr(0, 2);
  for (var i = 0; i < hexDigits; ++i) {
    h += hexValue.substr(2 + (hexDigits - 1 - i) * 2, 2);
  }
  return h;
}


function hexToFloat(hex) {
  var s = hex >> 31 ? -1 : 1;
  var e = (hex >> 23) & 0xFF;
  return s * (hex & 0x7fffff | 0x800000) * 1.0 / Math.pow(2, 23) * Math.pow(2, (e - 127))
}

function yourStringToFloat(str){

    return hexToFloat(flipHexString("0x"+str.substr(10), 8))

}

console.log(yourStringToFloat('450934644ad7a38441'));