Table of Contents:

1.  Introduction

1.1 ​ What is LoRaWAN Distance Detection Sensor


The Dragino LDDS75 is a  LoRaWAN Distance Detection Sensor for Internet of Things solution. It is used to measure the distance between the sensor and a flat object. The distance detection sensor is a module that uses  ultrasonic sensing technology for distance measurement, and  temperature compensation is performed internally to improve the reliability of data. The LDDS75 can be applied to scenarios such as horizontal distance measurement, liquid level measurement, parking management system, object proximity and presence detection, intelligent trash can management system, robot obstacle avoidance, automatic control, sewer, bottom water level monitoring, etc.

It detects the distance  between the measured object and the sensor, and uploads the value via wireless to LoRaWAN IoT Server.

The LoRa wireless technology used in LDDS75 allows device to send data and reach extremely long ranges at low data-rates. It provides ultra-long range spread spectrum communication and high interference immunity whilst minimizing current consumption.

LDDS75 is powered by  4000mA or 8500mAh Li-SOCI2 battery; It is designed for long term use up to 10 years*.

Each LDDS75 pre-loads with a set of unique keys for LoRaWAN registrations, register these keys to local LoRaWAN server and it will auto connect if there is network coverage, after power on.

 * Actually lifetime depends on network coverage and uplink interval and other factors.


​1.2  Features

  • LoRaWAN 1.0.3 Class A
  • Ultra low power consumption
  • Distance Detection by Ultrasonic technology
  • Flat object range 280mm - 7500mm
  • Accuracy: ±(1cm+S*0.3%) (S: Distance)
  • Cable Length : 25cm
  • Bands: CN470/EU433/KR920/US915/EU868/AS923/AU915/IN865
  • AT Commands to change parameters
  • Uplink on periodically
  • Downlink to change configure
  • IP66 Waterproof Enclosure
  • 4000mAh or 8500mAh Battery for long term use

1.3  Specification

1.3.1  Rated environmental conditions


Minimum value

Typical value

Maximum value

Storage temperature-252580 
Storage humidity 65%90%RH(1)
Operating temperature-152560 
Working humidity




Remarks: (1)  a. When the ambient temperature is 0-39 ℃, the maximum humidity is 90% (non-condensing);       

                       b. When the ambient temperature is 40-50 ℃, the highest humidity is the highest humidity in the natural world at the current temperature (no condensation)

1.3.2  Effective measurement range Reference beam pattern

(1) The tested object is a white cylindrical tube made of PVC, with a height of 100cm and a diameter of 7.5cm.


(2) The object to be tested is a "corrugated cardboard box" perpendicular to the central axis of 0 °, and the length * width is 60cm * 50cm.


1.4 ​ Applications

  • Horizontal distance measurement
  • Liquid level measurement
  • Parking management system
  • Object proximity and presence detection
  • Intelligent trash can management system
  • Robot obstacle avoidance
  • Automatic control
  • Sewer
  • Bottom water level monitoring

1.5  Pin mapping and power on


2.  Configure LDDS75 to connect to LoRaWAN network

2.1  How it works

The LDDS75 is configured as LoRaWAN OTAA Class A mode by default. It has OTAA keys to join LoRaWAN network. To connect a LoRaWAN network, you need to input the OTAA keys in the LoRaWAN IoT server and power on the LDDS75. If there is coverage of the LoRaWAN network, it will automatically join the network via OTAA and start to send the sensor value

In case you can't set the OTAA keys in the LoRaWAN OTAA server, and you have to use the keys from the server, you can use AT Commands to set the keys in the LDDS75.

2.2  ​Quick guide to connect to LoRaWAN server (OTAA)

Following is an example for how to join the TTN v3 LoRaWAN Network. Below is the network structure; we use the LG308  as a LoRaWAN gateway in this example. 


The LG308 is already set to connected to TTN network , so what we need to now is configure the TTN server.


Step 1: Create a device in TTN with the OTAA keys from LDDS75.

Each LDDS75 is shipped with a sticker with the default device keys, user can find this sticker in the box. it looks like below.


For OTAA registration, we need to set APP EUI/ APP KEY/ DEV EUI. Some server might no need to set APP EUI.

Enter these keys in the LoRaWAN Server portal. Below is TTN V3 screen shot:


Add APP EUI in the application





You can also choose to create the device manually.




Step 2: Power on LDDS75

Put a Jumper on JP2 to power on the device. ( The Switch must be in FLASH position).


Step 3: The LDDS75 will auto join to the TTN network. After join success, it will start to upload messages to TTN and you can see the messages in the panel.


2.3  ​Uplink Payload

LDDS75 will uplink payload via LoRaWAN with below payload format:  

Uplink payload includes in total 4 bytes.
Payload for firmware version v1.1.4. . Before v1.1.3, there is on two fields: BAT and Distance




(unit: mm)

Digital Interrupt (Optional)Sensor Flag


2.3.1  Battery Info

Check the battery voltage for LDDS75.

Ex1: 0x0B45 = 2885mV

Ex2: 0x0B49 = 2889mV

2.3.2  Distance

Get the distance. Flat object range 280mm - 7500mm.

For example, if the data you get from the register is 0x0B 0x05, the distance between the sensor and the measured object is 

0B05(H) = 2821 (D) = 2821 mm.

  • If the sensor value is 0x0000, it means system doesn't detect ultrasonic sensor.
  • If the sensor value lower than 0x0118 (280mm), the sensor value will be invalid. Since v1.1.4, all value lower than 280mm will be set to 0x0014(20mm) which means the value is invalid.

2.3.3  Interrupt Pin

This data field shows if this packet is generated by interrupt or not. Click here for the hardware and software set up.


0x00: Normal uplink packet.

0x01: Interrupt Uplink Packet.

2.3.4  DS18B20 Temperature sensor

This is optional, user can connect external DS18B20 sensor to the +3.3v, 1-wire and GND pin . and this field will report temperature.


If payload is: 0105H:  (0105 & FC00 == 0), temp = 0105H /10 = 26.1 degree

If payload is: FF3FH :  (FF3F & FC00 == 1) , temp = (FF3FH - 65536)/10 = -19.3 degrees.

Note: DS18B20 feature is supported in the hardware version > v1.3 which made since early of 2021.

2.3.5  Sensor Flag

0x01: Detect Ultrasonic Sensor

0x00: No Ultrasonic Sensor

2.3.6  Decode payload in The Things Network

While using TTN network, you can add the payload format to decode the payload.


The payload decoder function for TTN V3 is here:

LDDS75 TTN V3 Payload Decoder:  ttps://github.com/dragino/dragino-end-node-decoder

2.4  Uplink Interval

The LDDS75 by default uplink the sensor data every 20 minutes. User can change this interval by AT Command or LoRaWAN Downlink Command. See this link: Change Uplink Interval

2.5  ​Show Data in DataCake IoT Server

DATACAKE provides a human friendly interface to show the sensor data, once we have data in TTN, we can use DATACAKE to connect to TTN and see the data in DATACAKE. Below are the steps:


Step 1: Be sure that your device is programmed and properly connected to the network at this time.

Step 2: To configure the Application to forward data to DATACAKE you will need to add integration. To add the DATACAKE integration, perform the following steps:



Step 3: Create an account or log in Datacake.

Step 4: Search the LDDS75 and add DevEUI.


After added, the sensor data arrive TTN V3, it will also arrive and show in Datacake.


2.6  Frequency Plans

The LDDS75 uses OTAA mode and below frequency plans by default. If user want to use it with different frequency plan, please refer the AT command sets.

2.6.1  EU863-870 (EU868)


868.1 - SF7BW125 to SF12BW125

868.3 - SF7BW125 to SF12BW125 and SF7BW250

868.5 - SF7BW125 to SF12BW125

867.1 - SF7BW125 to SF12BW125

867.3 - SF7BW125 to SF12BW125

867.5 - SF7BW125 to SF12BW125

867.7 - SF7BW125 to SF12BW125

867.9 - SF7BW125 to SF12BW125

868.8 - FSK



Uplink channels 1-9 (RX1)

869.525 - SF9BW125 (RX2 downlink only)

2.6.2  US902-928(US915)

Used in USA, Canada and South America. Default use CHE=2


903.9 - SF7BW125 to SF10BW125

904.1 - SF7BW125 to SF10BW125

904.3 - SF7BW125 to SF10BW125

904.5 - SF7BW125 to SF10BW125

904.7 - SF7BW125 to SF10BW125

904.9 - SF7BW125 to SF10BW125

905.1 - SF7BW125 to SF10BW125

905.3 - SF7BW125 to SF10BW125


923.3 - SF7BW500 to SF12BW500

923.9 - SF7BW500 to SF12BW500

924.5 - SF7BW500 to SF12BW500

925.1 - SF7BW500 to SF12BW500

925.7 - SF7BW500 to SF12BW500

926.3 - SF7BW500 to SF12BW500

926.9 - SF7BW500 to SF12BW500

927.5 - SF7BW500 to SF12BW500

923.3 - SF12BW500(RX2 downlink only)


2.6.3  CN470-510 (CN470)

Used in China, Default use CHE=1


486.3 - SF7BW125 to SF12BW125

486.5 - SF7BW125 to SF12BW125

486.7 - SF7BW125 to SF12BW125

486.9 - SF7BW125 to SF12BW125

487.1 - SF7BW125 to SF12BW125

487.3 - SF7BW125 to SF12BW125

487.5 - SF7BW125 to SF12BW125

487.7 - SF7BW125 to SF12BW125



506.7 - SF7BW125 to SF12BW125

506.9 - SF7BW125 to SF12BW125

507.1 - SF7BW125 to SF12BW125

507.3 - SF7BW125 to SF12BW125

507.5 - SF7BW125 to SF12BW125

507.7 - SF7BW125 to SF12BW125

507.9 - SF7BW125 to SF12BW125

508.1 - SF7BW125 to SF12BW125

505.3 - SF12BW125 (RX2 downlink only)

2.6.4  AU915-928(AU915)

Default use CHE=2


916.8 - SF7BW125 to SF12BW125

917.0 - SF7BW125 to SF12BW125

917.2 - SF7BW125 to SF12BW125

917.4 - SF7BW125 to SF12BW125

917.6 - SF7BW125 to SF12BW125

917.8 - SF7BW125 to SF12BW125

918.0 - SF7BW125 to SF12BW125

918.2 - SF7BW125 to SF12BW125


923.3 - SF7BW500 to SF12BW500

923.9 - SF7BW500 to SF12BW500

924.5 - SF7BW500 to SF12BW500

925.1 - SF7BW500 to SF12BW500

925.7 - SF7BW500 to SF12BW500

926.3 - SF7BW500 to SF12BW500

926.9 - SF7BW500 to SF12BW500

927.5 - SF7BW500 to SF12BW500

923.3 - SF12BW500(RX2 downlink only)


2.6.5  AS920-923 & AS923-925 (AS923)

Default Uplink channel:

923.2 - SF7BW125 to SF10BW125

923.4 - SF7BW125 to SF10BW125


Additional Uplink Channel:

(OTAA mode, channel added by JoinAccept message)


AS920~AS923 for Japan, Malaysia, Singapore:

922.2 - SF7BW125 to SF10BW125

922.4 - SF7BW125 to SF10BW125

922.6 - SF7BW125 to SF10BW125

922.8 - SF7BW125 to SF10BW125

923.0 - SF7BW125 to SF10BW125

922.0 - SF7BW125 to SF10BW125


AS923 ~ AS925 for Brunei, Cambodia, Hong Kong, Indonesia, Laos, Taiwan, Thailand, Vietnam:

923.6 - SF7BW125 to SF10BW125

923.8 - SF7BW125 to SF10BW125

924.0 - SF7BW125 to SF10BW125

924.2 - SF7BW125 to SF10BW125

924.4 - SF7BW125 to SF10BW125

924.6 - SF7BW125 to SF10BW125



Uplink channels 1-8 (RX1)

923.2 - SF10BW125 (RX2)

2.6.6  KR920-923 (KR920)

Default channel:

922.1 - SF7BW125 to SF12BW125

922.3 - SF7BW125 to SF12BW125

922.5 - SF7BW125 to SF12BW125


Uplink: (OTAA mode, channel added by JoinAccept message)

922.1 - SF7BW125 to SF12BW125

922.3 - SF7BW125 to SF12BW125

922.5 - SF7BW125 to SF12BW125

922.7 - SF7BW125 to SF12BW125

922.9 - SF7BW125 to SF12BW125

923.1 - SF7BW125 to SF12BW125

923.3 - SF7BW125 to SF12BW125



Uplink channels 1-7(RX1)

921.9 - SF12BW125 (RX2 downlink only; SF12BW125 might be changed to SF9BW125)

2.6.7  IN865-867 (IN865)


865.0625 - SF7BW125 to SF12BW125

865.4025 - SF7BW125 to SF12BW125

865.9850 - SF7BW125 to SF12BW125



Uplink channels 1-3 (RX1)

866.550 - SF10BW125 (RX2)

2.7  LED Indicator

The LDDS75 has an internal LED which is to show the status of different state. 

  • Blink once when device power on.
  • The device detects the sensor and flashes 5 times.
  • Solid ON for 5 seconds once device successful Join the network.
  • Blink once when device transmit a packet.

2.8  ​Firmware Change Log

Firmware Upgrade Method: Firmware Upgrade Instruction

2.9  Mechanical



2.10  Battery & Power Consumption

LSE01 uses ER26500 + SPC1520 battery pack. See below link for detail information about the battery info and how to replace.

Battery Info & Power Consumption Analyze .

3.  Configure LDDS75 via AT Command or LoRaWAN Downlink

Use can configure LDDS75 via AT Command or LoRaWAN Downlink.


There are two kinds of commands to configure LDDS75, they are:

  •  General Commands.

These commands are to configure:

  • General system settings like: uplink interval.

  • LoRaWAN protocol & radio related command.

They are same for all Dragino Device which support DLWS-005 LoRaWAN Stack. These commands can be found on the wiki: End Device AT Commands and Downlink Command


  •  Commands special design for LDDS75

These commands only valid for LDDS75, as below:

3.1  Access AT Commands

LDDS75 supports AT Command set in the stock firmware. You can use a USB to TTL adapter to connect to LDDS75 for using AT command, as below.


Or if you have below board, use below connection:


In the PC, you need to set the serial baud rate to 9600 to access the serial console for LDDS75. LDDS75 will output system info once power on as below:


3.2  Set Transmit Interval Time

Feature: Change LoRaWAN End Node Transmit Interval.

AT Command: AT+TDC

Command ExampleFunctionResponse
AT+TDC=?Show current transmit Interval

the interval is 30000ms = 30s

AT+TDC=60000Set Transmit Interval

Set transmit interval to 60000ms = 60 seconds

Downlink Command: 0x01

Format: Command Code (0x01) followed by 3 bytes time value.

If the downlink payload=0100003C, it means set the END Node's Transmit Interval to 0x00003C=60(S), while type code is 01.

  • Example 1: Downlink Payload: 0100001E // Set Transmit Interval (TDC) = 30 seconds
  • Example 2: Downlink Payload: 0100003C // Set Transmit Interval (TDC) = 60 seconds

3.3  Set Interrupt Mode

Feature, Set Interrupt mode for GPIO_EXIT.

Downlink Command: AT+INTMOD

Command ExampleFunctionResponse
AT+INTMOD=?Show current interrupt mode

the mode is 0 =No Interruption


Set Transmit Interval
0. (Disable Interrupt),
1. (Trigger by rising and falling edge)
2. (Trigger by falling edge)
3. (Trigger by rising edge)


Downlink Command: 0x06

Format: Command Code (0x06) followed by 3 bytes.

This means that the interrupt mode of the end node is set to 0x000003=3 (rising edge trigger), and the type code is 06.

  • Example 1: Downlink Payload: 06000000      // Turn off interrupt mode
  • Example 2: Downlink Payload: 06000003      // Set the interrupt mode to rising edge trigger

4.  FAQ

4.1  What is the frequency plan for LDDS75?

LDDS75 use the same frequency as other Dragino products. User can see the detail from this link:  Introduction

4.2  How to change the LoRa Frequency Bands/Region

You can follow the instructions for how to upgrade image.
When downloading the images, choose the required image file for download. ​

4.3  Can I use LDDS75 in condensation environment?

LDDS75 is not suitable to be used in condensation environment. Condensation on the LDDS75 probe will affect the reading and always got 0.

5.  Trouble Shooting

5.1  Why I can't join TTN V3 in US915 / AU915 bands?

It is due to channel mapping. Please see below link:  Frequency band

5.2  AT Command input doesn't work

In the case if user can see the console output but can't type input to the device. Please check if you already include the ENTER while sending out the command. Some serial tool doesn't send ENTER while press the send key, user need to add ENTER in their string. 


5.3  Why does the sensor reading show 0 or "No sensor"

1. The measurement object is very close to the sensor, but in the blind spot of the sensor.

2. Sensor wiring is disconnected

3. Not using the correct decoder

5.4  Abnormal readings The gap between multiple readings is too large or the gap between the readings and the actual value is too large

1) Please check if there is something on the probe affecting its measurement (condensed water, volatile oil, etc.)

2) Does it change with temperature, temperature will affect its measurement

3) If abnormal data occurs, you can turn on DEBUG mode, Please use downlink or AT COMMAN to enter DEBUG mode.

downlink command: F1 01, AT command: AT+DDEBUG=1

4) After entering the debug mode, it will send 20 pieces of data at a time, and you can send its uplink to us for analysis


Its original payload will be longer than other data. Even though it is being parsed, it can be seen that it is abnormal data.

Please send the data to us for check.

6.  Order Info

Part Number : LDDS75-XX-YY

XXThe default frequency band

  • AS923 : LoRaWAN AS923 band
  • AU915 : LoRaWAN AU915 band
  • EU433 : LoRaWAN EU433 band
  • EU868 : LoRaWAN EU868 band
  • KR920 : LoRaWAN KR920 band
  • US915 : LoRaWAN US915 band
  • IN865 :  LoRaWAN IN865 band
  • CN470 : LoRaWAN CN470 band

YY: Battery Option

  • 4000mAh battery
  • : 8500mAh battery

7. ​ Packing Info

Package Includes:

  • LDDS75 LoRaWAN Distance Detection Sensor x 1

Dimension and weight:

  • Device Size: cm
  • Device Weight: g
  • Package Size / pcs : cm
  • Weight / pcs : g

8.  ​Support

  • Support is provided Monday to Friday, from 09:00 to 18:00 GMT+8. Due to different timezones we cannot offer live support. However, your questions will be answered as soon as possible in the before-mentioned schedule.
  • Provide as much information as possible regarding your enquiry (product models, accurately describe your problem and steps to replicate it etc) and send a mail to support@dragino.com.
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