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lora-devices-ttn

Dragino - LHT65N-E5

The LHT65N-E5 includes a built-in SHT20 temperature/humidity sensor and a jack to connect an external sensor e.g. a BH1750 based brightness/illumination sensor.

Table of contents

  1. Specifications
  2. Documents
  3. Ordering Info
    1. Device Configuration
  4. Optional Settings
    1. Change sampling interval
      1. Examples

Specifications

  • indoor device (external sensor placement possible)
  • Price ca. CHF 50.- (27.09.2024)
  • Built-in sensors
    • Temperature, -40 … +80 [°C], ± 0.3 °C
    • relative Humidity, 0 … 99.9 [%rH], ± 3 %rH
  • External sensor
    • Brightness, 0 … 65’535 [lux], ± 1 lux
  • Power Supply: 1 battery, 3.0 V, 2400 mAh (CR17450), Li-MnO₂
    • Expected life time: 8 … 10 years at roomtemperature
  • Min voltage: 2.45 V
  • Size: 43 × 93 × 28 mm
  • Weight: 105 g

Documents

Ordering Info

  • Part Number: LHT65N-XXX-YY
    • XXX is frequency band
    • YY is external sensor
  • Version with external temperature sensor: LHT65N-EU868-E3
  • Ordering Link

Device Configuration

  • Now you can see the incoming telegrams in the tab Data, but their content, the payload, is cryptic…!
  • We need to tell the “The Things Network” where to find e.g. the temperature etc. in these cryptic numbers and letters. We can do that with configuring a “Payload Decoder Function”.
  1. Log in and open the application
  2. Select the tab Payload Formats > decoder and copy/paste the following code:
function str1(str2) {
    let str3 = "";
    for (let i = 0; i < str2.length; i++) {
        if (str2[i] <= 0x0F) {
            str2[i] = "0" + str2[i].toString(16);
        }
        str3 += str2[i].toString(16);
    }
    return str3;
}

function strPad(byte) {
    const zero = '00';
    const hex = byte.toString(16);
    const tmp = 2 - hex.length;
    return zero.substr(0, tmp) + hex + " ";
}

function dataLog(i, bytes) {
    let ext = bytes[6] & 0x0F;
    let bb;
    if (ext === 1 || ext === 9 || ext === 2 || ext === 11) {
        bb = parseFloat(((bytes[0 + i] << 24 >> 16 | bytes[1 + i]) / 100).toFixed(2));
    } else if (ext === 4) {
        let extiPinLevel = bytes[0 + i] ? "High" : "Low";
        let extiStatus = bytes[1 + i] ? "True" : "False";
        bb = extiPinLevel + extiStatus;
    } else if (ext === 5 || ext === 7 || ext === 8 || ext === 14) {
        bb = bytes[0 + i] << 8 | bytes[1 + i];
    } else if (ext === 6) {
        bb = (bytes[0 + i] << 8 | bytes[1 + i]) / 1000;
    }
    let cc = parseFloat(((bytes[2 + i] << 24 >> 16 | bytes[3 + i]) / 100).toFixed(2));
    let dd = parseFloat((((bytes[4 + i] << 8 | bytes[5 + i]) & 0xFFF) / 10).toFixed(1));
    let ee = getMyDate((bytes[7 + i] << 24 | bytes[8 + i] << 16 | bytes[9 + i] << 8 | bytes[10 + i]).toString(10));
    let string = '[' + bb + ',' + cc + ',' + dd + ',' + ee + ']' + ',';
    return string;
}

function getzf(num) {
    if (parseInt(num) < 10) {
        num = '0' + num;
    }
    return num;
}

function getMyDate(str) {
    let date;
    if (str > 9999999999) {
        date = new Date(parseInt(str));
    } else {
        date = new Date(parseInt(str) * 1000);
    }
    let year = date.getFullYear();
    let month = date.getMonth() + 1;
    let day = date.getDate();
    let hour = date.getHours();
    let min = date.getMinutes();
    let sec = date.getSeconds();
    return year + '-' + getzf(month) + '-' + getzf(day) + ' ' + getzf(hour) + ':' + getzf(min) + ':' + getzf(sec);
}

function Decoder(bytes, port) {
    let ext = bytes[6] & 0x0F;
    let pollMessageStatus = (bytes[6] >> 6) & 0x01;
    let retransmissionStatus = (bytes[6] >> 7) & 0x01;
    let connect = (bytes[6] & 0x80) >> 7;
    let decode = {};
    let data = {};
    if (port === 3 && (bytes[2] === 0x01 || bytes[2] === 0x02 || bytes[2] === 0x03 || bytes[2] === 0x04)) {
        let array1 = [];
        let bytes1 = "0x";
        let str1 = str1(bytes);
        let str2 = str1.substring(0, 6);
        let str3 = str1.substring(6);
        let reg = /.{4}/g;
        let rs = str3.match(reg);
        rs.push(str3.substring(rs.join('').length));
        rs.pop();
        let newArr = [...rs];
        let data1 = newArr;
        decode.bat = parseInt(bytes1 + str2.substring(0, 4) & 0x3FFF);
        switch (parseInt(bytes1 + str2.substring(4))) {
            case 1:
                decode.sensor = "ds18b20";
                break;
            case 2:
                decode.sensor = "tmp117";
                break;
            case 3:
                decode.sensor = "gxht30";
                break;
            case 4:
                decode.sensor = "sht31";
                break;
        }
        for (let i = 0; i < data1.length; i++) {
            let temp = (parseInt(bytes1 + data1[i].substring(0, 4))) / 100;
            array1[i] = temp;
        }
        decode.Temp = array1;
        return decode;
    } else if (port === 5) {
        let sensor;
        switch (bytes[0]) {
            case 0x0B:
                sensor = "LHT65N";
                break;
            case 0x1A:
                sensor = "LHT65N-PIR";
                break;
        }
        subBand = bytes[4] === 0xff ? "NULL" : bytes[4];
        switch (bytes[3]) {
            case 0x01:
                freqBand = "EU868";
                break;
            case 0x02:
                freqBand = "US915";
                break;
            // Add cases for other frequency bands as necessary
        }
        let firmVer = (bytes[1] & 0x0f) + '.' + (bytes[2] >> 4 & 0x0f) + '.' + (bytes[2] & 0x0f);
        let bat = (bytes[5] << 8 | bytes[6]) / 1000;
        return {
            SENSOR_MODEL: sensor,
            FIRMWARE_VERSION: firmVer,
            BAT: bat,
        };
    }
    if (retransmissionStatus === 0) {
        switch (pollMessageStatus) {
            case 0:
                if (ext === 0x09) {
                    decode["temperature_degrC@external"] = parseFloat(((bytes[0] << 24 >> 16 | bytes[1]) / 100).toFixed(2));
                    decode.battery_state = bytes[4] >> 6;
                } else {
                    decode.battery_volt = ((bytes[0] << 8 | bytes[1]) & 0x3FFF) / 1000;
                    decode.battery_state = bytes[0] >> 6;
                }
                if (ext !== 0x0f) {
                    decode["temperature_degrC@internal"] = parseFloat(((bytes[2] << 24 >> 16 | bytes[3]) / 100).toFixed(2));
                    decode["humidity_perc@internal"] = parseFloat((((bytes[4] << 8 | bytes[5]) & 0xFFF) / 10).toFixed(1));
                }
                if (ext === 1 || ext === 2) {
									if ((bytes[7] !== 0xFF) && (bytes[8] !== 0xFF)) {
										let value = parseFloat(((bytes[7] << 24 >> 16 | bytes[8]) / 100).toFixed(2));
                    decode["temperature_degrC@external"] = value;
									}
                } else if (ext === 5) {	
									if ((bytes[7] !== 0xFF) && (bytes[8] !== 0xFF)) {
										let value = bytes[7] << 8 | bytes[8];
									  decode["brightness_lux@external"] = value;
									}
                } else if (ext === 11) {
                    decode["temperature_degrC@external"] = parseFloat(((bytes[7] << 24 >> 16 | bytes[8]) / 100).toFixed(2));
                    decode["humidity_perc@external"] = parseFloat((((bytes[9] << 8 | bytes[10]) & 0xFFF) / 10).toFixed(1));
                }
                if ((bytes.length === 11) || (bytes.length === 15)) {
                    return decode;
                }
                break;
            default:
                return {
                    errors: ["unknown"]
                };
        }
    } else {
        switch (retransmissionStatus) {
            case 1:
                for (let i = 0; i < bytes.length; i = i + 11) {
                    let da = dataLog(i, bytes);
                    if (i === 0)
                        data.retransmission_message = da;
                    else
                        data.retransmission_message += da;
                }
                return data;
            default:
                return {
                    errors: ["unknown"]
                };
        }
    }
}
  1. Copy/Paste the following test payload into the field Payload and press Test
    CC 15 09 8C 02 7B 05 00 06 7F FF
  2. You should see the following result
    {
  "battery_state": 3,
  "battery_volt": 3.093,
  "brightness_lux@external": 6,
  "humidity_perc@internal": 63.5,
  "temperature_degrC@internal": 24.44
}
    • BatV -> battery voltage [V]
    • Ext_sensor -> connected external sensor
    • Hum_SHT -> Humidity internal sensor [%rH]
    • TempC_DS -> Temperature external sensor [°C]
    • TempC_SHT -> Temperature internal sensor [°C]
  3. Press save payload functions
  • Now you should be able to see the decoded data of your sensor in the tab Data.
  • Trigger a new telegram by pressing the ACT-button on the dragino LHT65 for a short time (> 1s and < 3s).

  • The dragino LHT65 sends a telegram once every 10 minutes.

Optional Settings

Change sampling interval

To change the sampling interval, you have to send the device configuration telegrams (Downlink-Messages) The time interval in minutes at which the sensor queries the current values.

  1. In the TTN Console on the device view, select the device and change to the tab Messaging, select Downlink
  2. Change the FPort to 2
  3. Copy/paste the payload, e.g. 0100012C into the Payload field to set interval to 5 minutes
  4. Press Send
  5. In the Data tab you should now see the scheduled telegram. The wisely sensor only receives downlink data after a transmission. Therefore start a transmission by pressing the button on the back of the sensor (push once short, green led will illuminate)

Examples

‘0100’ is an identifier, the rest represents the sampling interval in hex

  • 5 Minutes Interval: ‘0100012C’ (300s in hex are ‘012C’)
  • 15 Minutes Interval: ‘01000384’ (900s in hex are ‘0384’)
  • 60 Minutes Interval: ‘01000E10’ (3600s in hex are ‘0E10’)