SIG/Ashx/SigFoxDecodeExample.aspx

<%@ Page Title="" Language="VB" MasterPageFile="~/Site.master" AutoEventWireup="false" CodeFile="SigFoxDecodeExample.aspx.vb" Inherits="Ashx_SigFoxDecodeExample" %>

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    <script type="text/javascript">

        //e.g. parseSigFox('10b67dcc0006efda3d9816c2')

        //In an attempt to make the code clearer, I will not be using ArrayBuffer 
        function hex2Bytes(val) {

            if (!val) {
                return [];
            }

            val = val.trim();

            if (val.startsWith('0x')) {
                val = val.substring(2); //get rid of starting '0x'
            }


            var numBytes = val.length / 2;
            var bytes = [];


            for (var i = 0; i < numBytes; i++) {
                bytes.push(parseInt(val.substring(i * 2, (i * 2) + 2), 16));
            }

            return bytes;
        }

        function parseLittleEndianInt32(buffer, offset) {
            return (buffer[offset + 3] << 24) +
                (buffer[offset + 2] << 16) +
                (buffer[offset + 1] << 8) +
                (buffer[offset]);
        }

        function parseLittleEndianInt16(buffer, offset) {
            return (buffer[offset + 1] << 8) +
                (buffer[offset]);
        }

        function parseLittleEndianInt16Bits(buffer, offset, bitOffset, bitLength) {
            var temp = parseLittleEndianInt16(buffer, offset);
            temp = temp >> bitOffset;
            var mask = 0xffff >> (16 - bitLength);
            return temp & mask;
        }

        //e.g. 10b67dcc0006efda3d9816c2
        function parseSigFox(data) {
            var buffer = hex2Bytes(data);

            if (!buffer) {
                return null;
            }

            var recordType = buffer[0] & 0x0f;

            switch (recordType) {
                case 0: //positional data
                    return parsePositionalData(buffer);

                case 1: //downlink ACK
                    return parseDownlinkAck(buffer);

                case 2: //device data
                    return parseDeviceStats(buffer);

                case 3: //extended positional data
                    return parseExtendedData(buffer);

                default:
                    return null;
            }
        }

        function parsePositionalData(buffer) {
            var flags = buffer[0] & 0xF0;
            var inTrip = (flags & 0x10) > 0;
            var lastFixFailed = (flags & 0x20) > 0;

            var latitudeRaw = parseLittleEndianInt32(buffer, 1);
            var longitudeRaw = parseLittleEndianInt32(buffer, 5);
            var headingRaw = buffer[9];
            var speedRaw = buffer[10];
            var batteryRaw = buffer[11];

            return {
                MessageType: 0,
                InTrip: inTrip,
                LastFixFailed: lastFixFailed,
                Latitude: latitudeRaw * 1e-7,
                Longitude: longitudeRaw * 1e-7,
                Heading: headingRaw * 2,
                SpeedKmH: speedRaw,
                BatteryVoltage: (batteryRaw * 25) / 1000.0
            };
        }

        function parseDownlinkAck(buffer) {
            var flags = buffer[0] & 0xF0;
            var downlinkAccepted = (flags & 0x10) > 0;

            var firmwareMajor = buffer[2];
            var firmwareMinor = buffer[3];

            var data = [];
            for (var i = 0; i < 8; i++) {
                data.push(i + 4);
            }

            return {
                MessageType: 1,
                DownlinkAccepted: downlinkAccepted,
                FirmwareVersion: firmwareMajor + '.' + firmwareMinor,
                DownlinkData: data
            };
        }

        function parseDeviceStats(buffer) {
            var uptimeWeeks = parseLittleEndianInt16Bits(buffer, 0, 4, 9/*bits*/);
            var txCountRaw = parseLittleEndianInt16Bits(buffer, 1, 5, 11 /*bits*/);
            var rxCountRaw = buffer[3];
            var tripCountRaw = parseLittleEndianInt16Bits(buffer, 4, 0, 13 /*bits*/);
            var gpsSuccessRaw = parseLittleEndianInt16Bits(buffer, 5, 5, 10 /*bits*/);
            var gpsFailuresRaw = parseLittleEndianInt16Bits(buffer, 6, 7, 8 /*bits*/);
            var averageFixTime = parseLittleEndianInt16Bits(buffer, 7, 7, 9/*bits*/);
            var averageFailTime = parseLittleEndianInt16Bits(buffer, 9, 0, 9/*bits*/);
            var averageFreshenTime = parseLittleEndianInt16Bits(buffer, 10, 1, 8/*bits*/);
            var wakeupsPerTrip = buffer[11] >> 1;

            return {
                MessageType: 2,
                UptimeWeeks: uptimeWeeks,
                TxCount: txCountRaw * 32,
                RxCount: rxCountRaw * 32,
                TripCount: tripCountRaw,
                GpsSuccessCount: gpsSuccessRaw * 32,
                GpsFailureCount: gpsFailuresRaw * 32,
                AverageFixTimeSeconds: averageFixTime,
                AverageFailTimeSeconds: averageFailTime,
                AverageFreshenTimeSeconds: averageFreshenTime,
                WakeUpsPerTrip: wakeupsPerTrip
            };
        }

        function parseExtendedData(buffer) {
            var headingRaw = buffer[0] >> 4;
            var latitudeRaw = buffer[1] + buffer[2] * 256 + buffer[3] * 65536;
            if (latitudeRaw >= 0x800000)    // 2^23
                latitudeRaw -= 0x1000000;   // 2^24
            var longitudeRaw = buffer[4] + buffer[5] * 256 + buffer[6] * 65536;
            if (longitudeRaw >= 0x800000)   // 2^23
                longitudeRaw -= 0x1000000;  // 2^24
            var posAccRaw = buffer[7];
            var batteryRaw = buffer[8];
            var speedRaw = buffer[9] & 0x3F;
            var inTrip = (buffer[9] & 0x40) > 0;
            var lastFixFailed = (buffer[9] & 0x80) > 0;

            return {
                MessageType: 3,
                Heading: headingRaw * 22.5,
                Latitude: (latitudeRaw * 256) / 1e7,
                Longitude: (longitudeRaw * 256) / 1e7,
                PosAccM: posAccRaw * 1,
                BatteryVoltage: (batteryRaw * 25) / 1000.0,
                SpeedKmH: speedRaw * 2.5,
                InTrip: inTrip,
                LastFixFailed: lastFixFailed
            };
        }

    </script>
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