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lora-devices-ttn

Dragino - LSN50v2-D20

The LSN50v2-D20 is a LoRaWAN Waterproof Outdoor Temperature Sensor with 1 external Probe.

Table of contents

  1. Specifications
  2. Documents/Links
  3. Ordering Info
  4. Device specific Information
    1. Switch on the device
  5. Adding the Device to TTN
  6. Optional Settings
    1. Change sampling interval
      1. Examples
  7. Payload Decoder

Specifications

  • indoor/outdoor device
  • 1 External Sensor (DS18B20, cable length 2 m)
    • Temperature, -55 … +125 [°C], ± 0.5 (max ±2.0 °C)
  • Power Supply: 1 built in 8500mAh Li-SOCI2 battery
    • Expected life time: depending on usage, 5 … 10 years
  • LoRaWAN version: 1.0.3
  • LoRaWAN device class: A
  • Protection: IP66
  • Operating Temperature: -40 … 85°C
  • Size: 124 × 63 × 42 mm

Ordering Info

  • Part Number: LSN50v2-D20-EU868
  • Remark: The LSN50v2-D20 is phased out at most distributors. The successor is the Dragino D20-LB (ca. CHF 65.-, 17.07.2026)
    • Attention: The D20-LB uses a different payload format, so this page and its payload decoder do not apply to it.

Device specific Information

Switch on the device

Out of the factory the device is switched off. To power on the LSN50v2-D20, open the case and set the jumper (connect the two pins):

Switching between active and sleep mode (switch off / on, reset)

Adding the Device to TTN

  • The JoinEUI, App EUI and the DevEUI should be on a sticker on the cardboard box.
  • Before a device can communicate via “The Things Network” we have to add it to an application.
  1. Create a new application
  2. Under End devices in the application click (+) Register end device
  3. Under Input method select Enter end device specifics manually
  4. Under Frequency plan select Europe 863-870 Mhz (SF9 for RX2 - recommended)
  5. Under LoRaWAN version select 1.0.3
  6. Under JoinEUI enter the App EUI from the App and press Confirm
  7. Enter as well the DevEUI and the AppKey from the App
  8. Set an end-device name
  9. Press Register end device
  10. Add the payload formatter from below, either to the device itself or if all devices in the app are from the same type, to the application
  11. Switch on the device
  12. Close the case
  • After Configuration, the device restarts automatically and tries to join the network
  • Now the device should join the network and you can see the incoming telegrams in the Live data section

Optional Settings

Change sampling interval

Out of the factory the device measures and transmits every 20 minutes.

To change the sampling interval, you have to send the device configuration telegrams (Downlink-Messages). The interval is the time in seconds (hex encoded) at which the sensor measures and transmits 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. 01000258 into the Payload field to set interval to 10 minutes
  4. Press Send
  5. In the Data tab you should now see the scheduled telegram. The device only receives downlink data after an uplink. Therefore either wait for the next periodic uplink or open the case and press the ACT button on the PCB once short to trigger an uplink

Examples

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

  • 5 Minutes Interval: ‘0100012C’ (300s in hex are ‘012C’)
  • 10 Minutes Interval: ‘01000258’ (600s in hex are ‘0258’)
  • 15 Minutes Interval: ‘01000384’ (900s in hex are ‘0384’)
  • 60 Minutes Interval: ‘01000E10’ (3600s in hex are ‘0E10’)

Payload Decoder

function mapBatteryVoltageAbs(voltage) {
  if (voltage < 3.35) {
    return 0; // Critical
  } else if (voltage < 3.45) {
    return 1; // Warning
  } else if (voltage < 3.55) {
    return 2; // Good
  } else {
    return 3; // Very Good
  }
}

function decodeUplink(input) {
  var port = input.fPort;
  var bytes = input.bytes;
  var mode = (bytes[6] & 0x7C) >> 2;
  var data = {};

  switch (port) {
    case 2:
      if (mode === 0) {
        data.battery_volt_abs = (bytes[0] << 8 | bytes[1]) / 1000;
				data.battery_state_abs = mapBatteryVoltageAbs(data.battery_volt_abs);
        data.alarm_state_abs = (bytes[6] & 0x01) ? 1 : 0;

        if ((bytes[2] == 0xff) && (bytes[3] == 0xff)) {
          data.temperature_degrC_abs = 32767.0;
        } else {
          data.temperature_degrC_abs = parseFloat(((bytes[2] << 24 >> 16 | bytes[3]) / 10).toFixed(1));
        }
      }

      if (bytes.length == 11) {
        return {
          data: data,
        };
      }
      return {
        errors: ["unexpected payload length"]
      };

    default:
      return {
        errors: ["unknown FPort"]
      };
  }
}