Last active
May 4, 2018 13:32
-
-
Save niondir/f88d5f0461a0ce12ab7bd926e51c082d to your computer and use it in GitHub Desktop.
Float32 and signed int32 decoder for TheThingsNetwork TTN Console
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
function decodeFloat32(bytes) { | |
var sign = (bytes & 0x80000000) ? -1 : 1; | |
var exponent = ((bytes >> 23) & 0xFF) - 127; | |
var significand = (bytes & ~(-1 << 23)); | |
if (exponent == 128) | |
return sign * ((significand) ? Number.NaN : Number.POSITIVE_INFINITY); | |
if (exponent == -127) { | |
if (significand == 0) return sign * 0.0; | |
exponent = -126; | |
significand /= (1 << 22); | |
} else significand = (significand | (1 << 23)) / (1 << 23); | |
return sign * significand * Math.pow(2, exponent); | |
} | |
function decodeInt16(bytes) { | |
if ((bytes & 1 << 15) > 0) { // value is negative (16bit 2's complement) | |
bytes = ((~bytes) & 0xffff) + 1; // invert 16bits & add 1 => now positive value | |
bytes = bytes * -1; | |
} | |
return bytes; | |
} | |
function int16_LE(bytes, idx) { | |
bytes = bytes.slice(idx || 0); | |
return bytes[0] << 0 | bytes[1] << 8; | |
} | |
function int32_LE(bytes, idx) { | |
bytes = bytes.slice(idx || 0); | |
return bytes[0] << 0 | bytes[1] << 8 | bytes[2] << 16 | bytes[3] << 24; | |
} | |
function Decoder(bytes, port) { | |
// Decode an uplink message from a buffer | |
// (array) of bytes to an object of fields. | |
var decoded = { | |
pressure: decodeFloat32(int32_LE(bytes, 0)), | |
temp: decodeInt16(int16_LE(bytes,4)) / 100, | |
}; | |
return decoded; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment