This guide will instruct you to convert bytes into common number formats and use them in the codec of Device-profile.

  • Converter from hex to other number formats: here
  • Converter between hex and other formats: here
  • The convertion function must be placed on the start of the codec.

From byte array to string

// To convert a byte array bytes to a string returnStr 
// To remove a null character at the end
var returnStr = String.fromCharCode.apply(String, bytes ).replace(/\0/g,'');

From 2 bytes to unsigned integer number

// Sample usage: Hex 1235 => number=4661
var number = bytes[0] << 8 | bytes[1]

From 4 bytes to unsigned long number

// Sample usage: Hex 00000dc8 => number=3528
var number = bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3]

From 4 bytes (2 registers) to float

// Float is 32-bit (4 bytes)
function hex2float(num) {
    var sign = (num & 0x80000000) ? -1 : 1; 		  // 1 bit. To check the sign bit on most left
    var exponent = ((num >> 23) & 0xff) - 127; 		  // 8 bits. 8 right bits. -127 to 128
    var mantissa = 1 + ((num & 0x7fffff) / 0x7fffff); // 23 bits
    return parseFloat((sign * mantissa * Math.pow(2, exponent)).toFixed(3));
}

// Sample usage: 11.11
var hex = 0x4131c28f;
alert(hex2float(hex));

From 8 bytes (4 registers) to double

// Double is 64-bit (8 bytes)
function hex2double(left, right) {
    var sign = (left & 0x80000000) ? -1 : 1; 		  // 1 bit. To check the sign bit on most left
    var e = (left >> 52 - 32 & 0x7ff) - 1023
    return (left & 0xfffff | 0x100000) * 1.0 / Math.pow(2,52-32) * Math.pow(2, e) + right * 1.0 / Math.pow(2, 52) * Math.pow(2, e)
}

// Sample usage: 0x40fb207000000001 => 1111111.00000000001
alert(hex2double(0x40fb2070, 0x00000001));

From 2 bytes to simple unsigned float number

// Sample usage: Hex 1235 => number=4661 => 466.1
var number = (bytes[0] << 8 | bytes[1]) / 10;
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