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ttn-v2-payload-decoder.js
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ttn-v2-payload-decoder.js
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// Entry Point of decoding
function Decoder(bytes, port) {
var functionCode = bytes[0];
var result = {
func: functionCode,
port: port,
payload: bytes.map(function (byte) { return pad(byte.toString(16).toUpperCase(), 2); }).join('')
};
if (functionCode === 12) {
// Device sends information package, has to be decoded differently
fillUpDecodedDeviceInformation(bytes, result);
} else {
// Device sends measurement package
fillUpDecodedMeasurements(bytes, result);
}
return result;
}
// Decode the device information package and append it to the result object
function fillUpDecodedDeviceInformation(bytes, result) {
result.battery_voltage = bytesToFloat(bytes.slice(14, 18));
result.battery_capacity_percentage = bytes[18];
result.humidity_percentage = bytes[19];
result.class_group_text = pad(bytes[2], 2) + '.' + pad(bytes[3], 2);
result.sw_version_text = pad(bytes[4], 2) + '.' + pad(bytes[5], 2);
result.serial_number = bytesToInt(bytes.slice(6, 10));
result.device_local_datetime = bytesToDate(bytes.slice(10, 14));
}
// Decode the device measurement package and append it to the result object
function fillUpDecodedMeasurements(bytes, result) {
// ct = connection type
result.ct = bytes[1];
result.channel = bytesToBinaryString(bytes.slice(2, 4), 2);
result.channelCount = result.channel.match(/1/g).length;
var channelsReverted = result.channel.split("").reverse().join("");
var firstIndex = channelsReverted.indexOf('1');
// Loop throug all additional package content. Every group of 4 Bytes
// contains information for another channel (Channel 1, Channel 2, ...)
for (var i = 1; i <= result.channelCount; i++) {
var msbIndex = i * 4;
var byteValue = bytes.slice(msbIndex, msbIndex + 4);
result[deviceTypesToChannelNames[result.ct][firstIndex]] = bytesToFloat(byteValue);
firstIndex = channelsReverted.indexOf('1', firstIndex + 1);
}
}
// Convert an array of bytes into a float: bytesToFloat([ 0x3B, 0x2F, 0x7A, 0x1A ]) => 0.0026775659061968327
// Based on https://stackoverflow.com/a/37471538 by Ilya Bursov
function bytesToFloat(bytes) {
// JavaScript bitwise operators yield a 32 bits integer, not a float.
// Assume MSB (most significant byte first).
var bits = bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3];
var sign = (bits >>> 31 === 0) ? 1.0 : -1.0;
var e = bits >>> 23 & 0xff;
var m = (e === 0) ? (bits & 0x7fffff) << 1 : (bits & 0x7fffff) | 0x800000;
var f = sign * m * Math.pow(2, e - 150);
return f;
}
// Convert an array of bytes into a binary string: bytesToBinaryString([ 0x25, 0x4D, 0x4F, 0xCA ]) => '00100101010011010100111111001010'
function bytesToBinaryString(bytes) {
var binary = '';
for (var i = 0, l = bytes.length; i < l; i++) {
var bits = bytes[i].toString(2);
while (bits.length < 8) {
bits = '0' + bits;
}
binary = binary + bits;
}
return binary;
}
// Convert an array of bytes into an integer: bytesToInt([ 0x25, 0x4D, 0x4F, 0xCA ]) => 625823690
function bytesToInt(bytes) {
var binaryString = bytesToBinaryString(bytes);
if (binaryString.length == 0) {
return 0;
}
return parseInt(binaryString, 2);
}
// Convert an array of bytes into a UTC date. The bytes array must represent
// the number of seconds since "2000-01-01T00:00:00.000": bytesToDate([ 0x25, 0x4D, 0x4F, 0xCA ]) => 2019-10-31 07:54:50
function bytesToDate(bytes) {
var zero = new Date('2000-01-01T00:00:00.000Z').getTime();
var time = bytesToInt(bytes) * 1000;
var date = new Date(zero + time);
var year = date.getUTCFullYear();
var month = pad(date.getUTCMonth() + 1, 2);
var day = pad(date.getUTCDate(), 2);
var hours = pad(date.getUTCHours(), 2);
var minutes = pad(date.getUTCMinutes(), 2);
var seconds = pad(date.getUTCSeconds(), 2);
return year + '-' + month + '-' + day + ' ' + hours + ':' + minutes + ':' + seconds;
}
// Prepends a number of "0" to a parameter. pad(7, 2) => '07'
function pad(num, size) {
var s = num.toString();
while (s.length < size) s = '0' + s;
return s;
}
var map = {
1: 'Pd (P1-P2)',
2: 'P1',
3: 'P2',
4: 'T',
5: 'TOB1',
6: 'TOB2',
7: 'PBaro',
8: 'TBaro',
9: 'Volt Inp. 1',
10: 'Volt Inp. 2',
11: 'Pd (P1-PBaro)',
12: 'Conductivity Tc',
13: 'Conductivity raw',
14: 'T (Conductivity)',
15: 'P1 (2)',
16: 'P1 (3)',
17: 'P1 (4)',
18: 'P1 (5)',
19: 'Counter input',
20: 'SDI12 CH1',
21: 'SDI12 CH2',
22: 'SDI12 CH3',
23: 'SDI12 CH4',
24: 'SDI12 CH5',
25: 'SDI12 CH6',
26: 'SDI12 CH7',
27: 'SDI12 CH8',
28: 'SDI12 CH9',
29: 'SDI12 CH10',
30: 'TOB1 (2)',
31: 'TOB1 (3)',
32: 'TOB1 (4)',
33: 'TOB1 (5)',
34: 'E',
35: 'F',
36: 'G',
37: 'mH20 (Pbaro)',
38: 'mH20 (P1-P2)',
39: 'mH20 (P1-P3)',
40: 'mH20 (P1-P4)',
41: 'mH20 (P1-P5)',
42: 'Conductivity Tc (2)',
43: 'Conductivity Tc (3)',
44: 'T (Conductivity) (2)',
45: 'T (Conductivity) (3)',
46: 'P2 (2)',
47: 'TOB2 (2)',
48: 'AquaMaster Flow Rate',
49: 'AquaMaster Pressure',
50: 'AquaMaster Custom Flow Units',
51: 'AquaMaster External Supply Voltage',
52: 'Tank Content 1',
53: 'Tank Content 2',
54: 'Tank Content 3',
};
var deviceTypesToChannelNames = {
0: [map[1], map[2], map[3], map[4], map[5], map[6]],
1: [map[1], map[2], map[3], map[4], map[5], map[6]],
2: [map[11], map[2], map[3], map[4], map[5], map[6], map[7], map[8]],
3: [map[11], map[2], map[3], map[4], map[5], map[6], map[7], map[8]],
4: [map[1], map[2], map[3], map[4], map[5], map[6], map[7], map[8], map[9], map[10]],
5: [map[11], map[2], map[3], map[4], map[5], map[6], map[7], map[8], map[9], map[10], map[11]],
6: [map[1], map[2], map[3], map[4], map[5], map[6], map[7], map[8], map[9], map[10], map[15], map[16], map[17], map[18], map[19]],
7: [map[7], map[8], map[9], map[10], map[20], map[21], map[22], map[23], map[24], map[25], map[26], map[27], map[28], map[29]],
8: [map[2], map[5], map[15], map[30], map[16], map[31], map[17], map[32], map[18], map[33], map[9], map[10], map[7], map[8], map[19]],
9: [map[1], map[2], map[3], map[14], map[5], map[6], map[7], map[8], map[9], map[10], map[12], map[13]],
10: [map[11], map[2], map[3], map[14], map[5], map[6], map[7], map[8], map[9], map[10], map[12], map[13]],
11: [map[2], map[5], map[12], map[14], map[15], map[30], map[42], map[44], map[16], map[31], map[43], map[45], map[7], map[8], map[19]],
13: [map[2], map[3], map[5], map[6], map[15], map[46], map[30], map[47], map[7], map[8], map[9], map[10], map[19]],
};