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lora-devices-ttn

Dragino - LDS02

The LDS02 is a LoRaWAN Window/Door sensor.

Table of contents

  1. Specifications
  2. Documents
  3. Ordering Info
  4. Adding the Device to TTN
  5. Optional Settings
    1. Change TDC (Transmit Time Interval resp. Keep Alive Interval)
  6. Payload Decoder

Specifications

  • indoor device
  • Price ca. CHF 22.- (03.08.2023)
  • Built-in sensors
    • Magnetic reed switch, [open/close]
  • Power Supply: 2 common AAA batteries, 1.5 V
    • Expected life time: depending on usage, 16’000 ~ 70’000 state changes
  • LoRaWAN version: 1.0.3
  • LoRaWAN device class: A
  • Size: 69.2 × 29.2 × 15 mm
  • Weight: 55 g

Documents

Ordering Info

  • Part Number: LDS02-XX
    • XX is frequency band, for ttn in Europe choose EU868
  • Ordering Link

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. Open the case and take out the batteries
  12. Replace the batteries and 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 TDC (Transmit Time Interval resp. Keep Alive Interval)

In some cases, the sensor has sent incorrect values. This can be remedied by reducing the TDC.

By default, the sensor sends a status message every day. This interval can be reduced to 1 hour (3600s -> HEX E10) as follows:

  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 1
  3. Copy/paste the payload from the examples below, e.g. 01 00 0E 10 into the Payload field
  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 wait max 1 day or manually open/close the window to trigger a new transmission.

Payload Decoder

function decodeUplink(input) {
    const bytes = input.bytes;
    const batteryVoltage = ((bytes[0] << 8 | bytes[1]) & 0x3FFF) / 1000;
    const doorStatus = (bytes[0] & 0x80) ? 1 : 0; // 1: open, 0: close
    const waterLeakStatus = (bytes[0] & 0x40) ? 1 : 0;
    const mode = bytes[2];
    const alarm = bytes[9] & 0x01;
  
    let data = {
        battery_volt: batteryVoltage
    };

    switch (input.fPort) {
        case 10:
            const times = bytes[3] << 16 | bytes[4] << 8 | bytes[5];
            const duration = bytes[6] << 16 | bytes[7] << 8 | bytes[8]; // units: min

            switch (mode) {
                case 1: 
                    data.open_state = doorStatus;
                    data.counter = times;
                    data.openDuration_min = duration;
                    data.alarm_state = alarm;
                    break;
                case 2: 
                    data.waterLeak_state = waterLeakStatus;
                    data.counter = times;
                    data.waterDuration_minutes = duration;
                    break;
                case 3: 
                    data.waterLeak_state = doorStatus || waterLeakStatus;
                    data.alarm_state = alarm;
                    break;
                default:
                    break;
            }
            break;
        default:
            return { errors: ["unknown FPort"] };
    }

    return { data: data };
}