Dragino non-contact liquid sensor NMDS120

The dragino NMDS120 is a non-contact NB-IoT liquid sensor, which is able to measure liquid level without actually having any probes in direct contact with the liquid itself, through the use of a microwave radar.

This can ease the installation of such device in difficult locations, and avoids possible contaminations by avoiding direct contact.

It supports sending data through UDP, MQTT and COAP over nb-iot.

Useful resources

Find here the useful resources:

๐Ÿ“˜

About the resources

The resources linked are for a slightly different model (NDDS75) but the configuration is the same.

Configuring the device

Register the device

The imei can be found on the top cover of the device, please register the device in your iotcreators project before attempting to connect the device to the network.

๐Ÿ“˜

Register the device

Register device to IoT Creators

Opening the device

Connect the antenna to the device, then unscrew the four screws that hold the waterproof cover in place. This is the top view of the board:

Inserting the sim card

To mount the sim card into the sim card tray, unscrew the "modem removal screw" as showed above and insert the sim card.

Please be sure to insert the sim card as shown in this photo:

Connecting the device to a computer

To connect the device to a computer, you will need a usb to serial converter, which supports 3V3 or 5V logic. The logic voltage level can be selected with the "logic voltage switch" switch.

๐Ÿšง

Set the correct voltage level

Please carefully setup the correct voltage level (3.3 or 5 volts) according to your usb-to-serial converter. Failing to do so may unrecoverably damage your device!

You need 3 cables to connect the device to a serial monitor: GND (ground), TX (transmit) and RX (receive).

Just connect the RX of the dragino sensor to the TX of the usb-to-serial converter, the TX of the dragino sensor to the RX of the usb-to-serialconverter and the GND of the dragino sensor to the GND of the usb-to-serial converter.

Baudrate must be set to 9600 bps

First startup

To boot up the device, please set up the power on jumper as shown in section "Opening the device" to power on the device. Please make sure that the device is correctly attached to a computer.

Open your favourite serial monitor (for example: miniterm on linux or arduino serial monitor on windows) and the device will start to output info about its startup like so:

16:24:32.861 -> [12589]NBIOT has responded.
16:24:37.191 -> [16922]Echo mode turned off successfully.
16:24:39.123 -> [18868]Model information:BC95-GV.
16:24:40.458 -> [20206]The IMEI number is:<your_imei_here>.
16:24:41.824 -> [21554]The IMSI number is:<your_imsi_here>.
16:24:43.157 -> Currently set frequency band:1,3,5,8,20,28

If the imsi is correctly read, it means that the sim card has been correctly inserted.

Enter configuration mode

To enter configuration mode, just input the correct password, which for this device is 12345678.

Just input

12345678

And if the password is correct, the device will respond

16:53:09.872 -> [122884]Password Correct

You can set a custom device ID (the default will be the device imei) with command

AT+DEUI=<device_id> (15 bytes)

This means you are not able to enter at commands to configure the device.

Setting network parameters

You will need to configure the usual iotcreators parameters in order to attach the device to the iotcreators, APN, server address and port, protocol. In this guide i will use UDP since it is the simplest one.

To configure the protocol, in this case we will use plain UDP, just input:

AT+PRO=2

To configure the APN (please take a look here to check the correct APN for your sim card, the one below is just an example) just input

AT+APN=scs.telekom.tma.iot

To configure the device to send data to the iotcreators UDP server, just input

AT+SERVADDR=172.27.131.100,15683

You can then restart the device with the reset button.The device will then try to attach to the network.

If the device fails to register to the network, thus you always receive signal strength indication = 99, it is likely that the device is not having enough time to register to it. In this case, you can issue command

AT+CSQTIME=10

๐Ÿšง

Troubleshooting CSQ=99,99 error

Dragino hosts this page here to help you troubleshoot this issue.

To set the network registration timeout to 10 minutes, which should be sufficient to conenct to the network.

Working mode

Sending data to iotcreators

๐Ÿšง

Register the device

Remember to register the device before sending data to iotcreators, see chapter above.

The device will automatically send data at the specified interval of time. Such interval can be configured with command

AT+TDC=<time_in_seconds>

You can immediately send collected data with command

AT+NOUD

Payload decoding

Before version 1.3.2

Payload structure is as such, 14 bytes:

Size (bytes)622121
ValueDevice IDBATVersionSignalDistance (mm)Interrupt

The payload can be decoded as such, a payload example of:

72403155615900640c6c19029200

Where

  • Device ID: 0x724031556159 = 724031556159
  • Version: 0x0064=100=1.0.0
  • BAT: 0x0c6c = 3180 mV = 3.180V
  • Signal: 0x19 = 25
  • Distance: 0x0292= 658 mm
  • Interrupt: 0x00 = 0

Firmware 1.3.2+

In this mode, uplink payload includes 69 bytes in total by default.

Each time the device uploads a data package, 8 sets of recorded data will be attached. Up to 32 sets of recorded data can be uploaded.

Size (bytes)82211124241-32 group
ValueDevice IDBATVersionSignalMODInterruptDistanceUNIX timestampDistanceUNIX timestamp...

The payload can be decoded as such, a payload example of:

f86778705021331700840cf41e010000396315537b00396319baf000396319ba3c00396319b98800396319b8d400396319b82000396319b76c00396319b6b800396319b604 

Where

  • Device ID: f867787050213317 = f867787050213317
  • Version: 0x0084=132=1.3.2
  • BAT: 0x0cf4 = 3316 mV = 3.316V
  • Signal: 0x1e = 30
  • Mod: 0x01 = 1
  • Interrupt: 0x00= 0
  • Distance: 0x0039= 57 = 57
  • Time stamp: 0x6315537b =1662342011 (Unix Epoch Time)
  • Distance,Time stamp: 00396319baf0
  • 8 sets of recorded data: Distance,Time stamp : 00396319ba3c,.......

๐Ÿ“˜

Convert UNIX timestamps to human readable timestamps

You can convert UNIX timestamps to human readable timestamps with this online tool here for example.

Code example

Here you can find a code example on how to decode data from this device:

๐Ÿ“˜

Uplink decoder

https://github.com/iotcreators/doclib-downloads/blob/master/device-integrations/Simple%20http%20application/src/decoders/dragino_nmds120.py

Forwarding data to your application endpoint

To forward data to your application endpoint, you can follow the user guide here:

๐Ÿ“˜

Forwarding data

5: Forward message to application