ESP32-PaxCounter/src/TTN/serialized_decoder.js

// Decoder for device payload encoder "SERIALIZED"
// copy&paste to TTN Console -> Applications -> PayloadFormat -> Decoder

function Decoder(bytes, port) {

    var decoded = {};

    if (port === 1) {
        // only counter data, no gps
        if (bytes.length == 4) {
            return decode(bytes, [uint16, uint16], ['wifi', 'ble']);
        }
        // combined counter and gps data
        if (bytes.length > 4) {
            return decode(bytes, [uint16, uint16, latlng, uint8, uint16, uint16], ['wifi', 'ble', 'coords', 'sats', 'hdop', 'altitude']);
        }
    }

    if (port === 2) {
        // device status data
        if (bytes.length == 10) {
            return decode(bytes, [uint16, unixtime, temperature], ['voltage', 'uptime', 'cputemp']);
        }
        // device config data
        if (bytes.length == 8) {
            return decode(bytes, [uint8, uint16, uint8, uint8, uint8, bitmap], ['lorasf', 'rssilimit', 'sendcycle', 'wifichancycle', 'blescantime', 'rgblum', 'flags']);
        }
    }

}


// ----- contents of /src/decoder.js --------------------------------------------
// https://github.com/thesolarnomad/lora-serialization/blob/master/src/decoder.js

var bytesToInt = function (bytes) {
    var i = 0;
    for (var x = 0; x < bytes.length; x++) {
        i |= +(bytes[x] << (x * 8));
    }
    return i;
};

var unixtime = function (bytes) {
    if (bytes.length !== unixtime.BYTES) {
        throw new Error('Unix time must have exactly 4 bytes');
    }
    return bytesToInt(bytes);
};
unixtime.BYTES = 4;

var uint8 = function (bytes) {
    if (bytes.length !== uint8.BYTES) {
        throw new Error('int must have exactly 1 byte');
    }
    return bytesToInt(bytes);
};
uint8.BYTES = 1;

var uint16 = function (bytes) {
    if (bytes.length !== uint16.BYTES) {
        throw new Error('int must have exactly 2 bytes');
    }
    return bytesToInt(bytes);
};
uint16.BYTES = 2;

var latLng = function (bytes) {
    if (bytes.length !== latLng.BYTES) {
        throw new Error('Lat/Long must have exactly 8 bytes');
    }

    var lat = bytesToInt(bytes.slice(0, latLng.BYTES / 2));
    var lng = bytesToInt(bytes.slice(latLng.BYTES / 2, latLng.BYTES));

    return [lat / 1e6, lng / 1e6];
};
latLng.BYTES = 8;

var temperature = function (bytes) {
    if (bytes.length !== temperature.BYTES) {
        throw new Error('Temperature must have exactly 2 bytes');
    }
    var isNegative = bytes[0] & 0x80;
    var b = ('00000000' + Number(bytes[0]).toString(2)).slice(-8)
        + ('00000000' + Number(bytes[1]).toString(2)).slice(-8);
    if (isNegative) {
        var arr = b.split('').map(function (x) { return !Number(x); });
        for (var i = arr.length - 1; i > 0; i--) {
            arr[i] = !arr[i];
            if (arr[i]) {
                break;
            }
        }
        b = arr.map(Number).join('');
    }
    var t = parseInt(b, 2);
    if (isNegative) {
        t = -t;
    }
    return t / 1e2;
};
temperature.BYTES = 2;

var humidity = function (bytes) {
    if (bytes.length !== humidity.BYTES) {
        throw new Error('Humidity must have exactly 2 bytes');
    }

    var h = bytesToInt(bytes);
    return h / 1e2;
};
humidity.BYTES = 2;

var bitmap = function (byte) {
    if (byte.length !== bitmap.BYTES) {
        throw new Error('Bitmap must have exactly 1 byte');
    }
    var i = bytesToInt(byte);
    var bm = ('00000000' + Number(i).toString(2)).substr(-8).split('').map(Number).map(Boolean);
    return ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
        .reduce(function (obj, pos, index) {
            obj[pos] = bm[index];
            return obj;
        }, {});
};
bitmap.BYTES = 1;

var decode = function (bytes, mask, names) {

    var maskLength = mask.reduce(function (prev, cur) {
        return prev + cur.BYTES;
    }, 0);
    if (bytes.length < maskLength) {
        throw new Error('Mask length is ' + maskLength + ' whereas input is ' + bytes.length);
    }

    names = names || [];
    var offset = 0;
    return mask
        .map(function (decodeFn) {
            var current = bytes.slice(offset, offset += decodeFn.BYTES);
            return decodeFn(current);
        })
        .reduce(function (prev, cur, idx) {
            prev[names[idx] || idx] = cur;
            return prev;
        }, {});
};

if (typeof module === 'object' && typeof module.exports !== 'undefined') {
    module.exports = {
        unixtime: unixtime,
        uint8: uint8,
        uint16: uint16,
        temperature: temperature,
        humidity: humidity,
        latLng: latLng,
        bitmap: bitmap,
        decode: decode
    };
}