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lora-devices-ttn

Dragino - LTC2-FT

The LTC2-FT is a LoRaWAN Waterproof Outdoor Temperature Sensor with 2 external PT100 Probes.
Attention: This is an older procuct, the successor is the LTC2-LB

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
  • Attention, LTC2-FT doesn’t include temperature sensors, you need to purchase them separately
  • Price LTC2-FT ca. CHF 66.- (07.04.2025) with 1 sensor
  • 2 External Temperature Sensors PT100 (support 3-wire), Cable Length 2m
  • 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: 150 × 120 × 55 mm

Ordering Info

Attention: This is an older procuct, the successor is the LTC2-LB

Device specific Information

Switch on the device

Out of the factory the device is switched off. To power on the LTC2-FT, 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, see above table
  • 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

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. 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 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’)
  • 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) {
  const port = input.fPort;
  const bytes = input.bytes;
  const data = {};

  // Helpers
  const u16 = (hi, lo) => ((hi << 8) | lo) & 0xFFFF;
  const i16 = (hi, lo) => (hi << 24 >> 16) | lo; // sign-extended 16-bit

  const NULL_MARKER = 0x8001;

  const toTemperature_0x01 = (hi, lo) => {
    const raw = u16(hi, lo);
    if (raw === NULL_MARKER) return null;                 // device's NULL flag
    return parseFloat((i16(hi, lo) / 100).toFixed(2));    // °C with 0.01 resolution
  };

  const toTemperature_0x02 = (hi, lo) => {
    return parseFloat((i16(hi, lo) / 10).toFixed(1));     // °C with 0.1 resolution
  };

  if (port !== 2) {
    return { errors: ["Unsupported FPort"] };
  }

  // ---- Common header ----
  const ext = bytes[2] & 0x0F;                   // operating mode
  const pollMessageStatus = (bytes[2] & 0x40) >> 6;

  // Battery: top 14 bits (mask 0x3FFF), in volts
  const battery_volt_abs = (((bytes[0] << 8) | bytes[1]) & 0x3FFF) / 1000;

  data.battery_volt_abs = battery_volt_abs;
  data.battery_state_abs = mapBatteryVoltageAbs(battery_volt_abs);

  // ---- Payload by mode ----
  if (ext === 0x01) {
    // Temperature, 0.01 °C resolution, with NULL marker
    data["temperature_degrC_abs@channel1"] = toTemperature_0x01(bytes[3], bytes[4]);
    data["temperature_degrC_abs@channel2"] = toTemperature_0x01(bytes[5], bytes[6]);

  } else if (ext === 0x02) {
    // Temperature, 0.1 °C resolution
    data["temperature_degrC_abs@channel1"] = toTemperature_0x02(bytes[3], bytes[4]);
    data["temperature_degrC_abs@channel2"] = toTemperature_0x02(bytes[5], bytes[6]);

  }

  return { data };
}