Getting started with LoraWAN and The Things Network

by Gilbert Tanner on Feb 26, 2020

Getting started with LoraWAN and The Things Network
The LoRaWAN® specification is a Low Power, Wide Area (LPWA)  networking protocol designed to wirelessly connect battery operated  'things' to the internet in regional, national or global networks, and  targets key Internet of Things (IoT) requirements such as bi-directional  communication, end-to-end security, mobility and localization services.  - Lora Alliance

The Things Network (TTN) is a project dedicated to building an open, free, and decentralized internet of things network.

In this article, I'll walk you through the process of creating a TTN account, sending data to TTN using an ESP32 and a RFM95 module, and retrieving that data using MQTT.

Creating a The Things Network Account

Create Account
Figure 1: Creating an TTN Account

To create a The Things Network Account navigate to https://www.thethingsnetwork.org/ and click on the "Sign up" button. After that, you'll need to enter a  username, email, and password. Be sure to enter a good username since you won't be able to change it after creating the account.

Adding a gateway

Gateways form the bridge between devices and The Things Network. Devices use low power networks like LoRaWAN to connect to the Gateway, while the Gateway uses high bandwidth networks like WiFi, Ethernet or Cellular to connect to The Things Network. All gateways within reach of a device will receive the device’s messages and forward them to The Things Network. The network will deduplicate the messages and select the best gateway to forward any messages queued for downlink. A single gateway can serve thousands of devices. - TTN Gateway documentation

If there already is a gateway within reach you won't need to buy one yourself since all gateways within reach of a device will receive and forward messages.

The Things Indoor Gateway

For my tests I used the The Things Indoor Gateway (TTIG), an 8 channel LoRaWAN gateway with LBT support, which is available for $69.

The Things Indoor Gateway (TTIG)
Figure 2: The Things Indoor Gateway (TTIG)

Buying The Things Indoor Gateway

Links:

  • RS Components - link
  • Connected Things - link
  • IoT Shop - DE - link
  • Allied Electronics - link

There are also lots of other gateways. For an extensive list check out the hardware section of the TTN gateway documentation.

Connecting the gateway to your WiFi (from the TTN docs)

  1. Press the reset button (small button at the back of the gateway next to the USB-C port) for 5 seconds until the LED blinks rapidly GREEN<->RED for a couple of times.
  2. Hold the SETUP (button at the top of the gateway, next to the LED) for 10 seconds until the LED blinks rapidly in RED.
  3. The gateway now exposes a WiFi AP whose SSID is MINIHUB-xxxxxx where xxxxxx is the last 6 digits of the gateway ID.
  4. The password for this network is printed on the back panel of the device under WiFi PW.
  5. After connecting to this network go to 192.168.4.1 using a web browser to access the WiFi config page.
  6. Select the WiFi network and enter the password if it’s a closed network.
  7. Select the “Save and Reboot” option.
  8. If your config is right,
  • The gateway will blink GREEN for a few seconds while it connects to this network.
  • Then, it will blink GREEN<->RED for a few seconds while it connects to the CUPS endpoint and fetches the necessary information to connect to the LNS traffic endpoint.

If your configuration was successful, the LED will be solid GREEN which means that the gateway is connected to the LoRaWAN network and is ready to handle packets.

Connection to the TTN Backend

Now, that your gateway is connected to the LoraWAN network you can register it inside TTN. For this, navigate to the gateways page and click "register gateway".

Register Gateway
Figure 3: Register Gateway

To connect this gateway to the The Things Network console, register the gateway using the Legacy Packet Forwarder option. The EUI of the gateway is derived from the first number below the QR code on the back of the TTN Indoor Gateway. To get the 8 byte EUI insert FFFE after the first 6 characters. The EUI can also be found at the bottom of the WiFi Setup page.

After adding the gateway EUI add the other details such as location, frequency plan and router.

Register Gateway
Figure 4: Register Gateway

After you're finished click the register gateway button. If your configuration was successful and you have any LoRaWAN nodes transmitting nearby you should start receiving packets.

Gateway traffic
Figure 5: Gateway traffic

If you don't have any nodes yet don't worry. You'll learn how to create an application and add a node in the next sections.

Creating an application

Next, you'll need to create an application. For this, navigate to the application page and click "add application".

Add Application
Figure 6: Add Application

Registering the device at The Things Network

Now that you've created an application you're ready to register a device.

Registering a device
Figure 7: Registering a device

After adding the device go to the Settings tab and change the Activation Method to ABP.

Change Activation Method
Figure 8: Changing Activation Method

Now you should see a device address, network session key, and app session key under the Overview tab. These three values will later be needed to get the script to work.

Device Overview
Figure 9: Device Overview

Install arduino-lmic

LMiC (formerly 'LoRa MAC in C') is IBM's LoRa library. Arduino-LMIC contains the IBM LMIC (LoraMAC-in-C) library, slightly modified to run in the Arduino environment, allowing using the SX1272, SX1276 transceivers and compatible modules (such as some HopeRF RFM9x modules).

To install the library:

  • go to Sketch > Include Library > Manage Libraries and search for lmic and install the IBM LMIC Framework library.

Wiring RFM95 and ESP32

RMF95 Pinout
Figure 10: RFM95 Pinout

The RFM95 communicates with the microcontroller over SPI. To get the module to communicate with the ESP32 correctly connect the pins as follows:

  • GND: GND
  • 3.3V: 3.3V
  • MISO: D19
  • MOSI: D23
  • SCK: D18
  • RESET/RST: D14
  • DIO0: 2
  • DIO1: 15
  • DIO2: 4
  • NSS: 5

Note: Of the three GND pins, only one needs to be connected.

Important: Don't forget to connect an antenna to the ANT pin.

Creating a sender script

The LMIC library already includes a script for The Things Network, which can be accessed under Examples > IBM LMIC Framework > ttn.

To get the script to work, you have to enter the Network Session Key,  App Session Key, and Device Address from the Overview tab of the  Device. You'll also have to update the lmic_pinmap lmic_pins variables depending on how you connected it to your microcontroller.

In my case, I used the following pins:

const lmic_pinmap lmic_pins = {
    .nss = 6,
    .rxtx = LMIC_UNUSED_PIN,
    .rst = 5,
    .dio = {2, 3, 4},
};

After running the file, you should see something like the following in the Serial Monitor.

Sending data
Figure 11: Sending data

You should now be able to see the send data in the Data tab of the application or device page.

Device data
Figure 12: Data Tab

Encoding/Decoding data

LoraWAN and TTN transfer raw bytes, which can be hard to read. That's the reason why libraries are provided to encode/decode data. For Arduino the Lora Serialization library can be used. The library allows you to encode your data on the Arduino side and decode it on the TTN side.

If you for example have temperature, humidity, pressure and sea_leavel readings you can encode/decode your data as follows:

Arduino side:

LoraMessage message;

message
    .addTemperature(temperature)
    .addHumidity(humidity)
    .addUnixtime(pressure)
    .addUint16(sea_level);

TTN side (Payload Formats):

// copy the content from src/decoder.js (https://github.com/thesolarnomad/lora-serialization/blob/master/src/decoder.js)
function Decoder(bytes, port) {
  var json = decode(bytes, [temperature, humidity, unixtime, uint16], ['temperature', 'humidity', 'pressure', 'sea_level']);
  return json;
}
Payload Formats
Figure 13: Payload Formats

If you now look at the data tab you'll be able to see the data as decoded elements.

Decoded data
Figure 14: Decoded data

Gateway data retrieval over MQTT

Now we are receiving the data in TTN, but how can we now get the data from TTN? TTN allows you to get the data over MQTT, an extremely lightweight machine-to-machine(M2M) connectivity protocol using a publish/subscribe model.

In the following examples, I'll show you how to receive data by using Mosquitto's CLI, but TTN also provides libraries for multiple programming languages, including Java, Node.js, and Python. For more information, check out the SDKs & Libraries section in the documentation.

Receiving Messages (up)

To receive data from a TTN application, execute the following command:

mosquitto_sub -h <Region>.thethings.network -t '+/devices/+/up' -u '<AppID>' -P '<AppKey>' -v

Don't forget to replace <Region>, <AppID>, <AppKey>  with the right values for your application. You can find them in the  Overview tab of your application. The region is can be found under Handler. You will only need the part that follows ttn-handler-, e.g. eu.

Note: -t stands for the topic do subscribe to. The topic has the following structure: AppID/devices/deviceID/up. Attributes between // can also be replaced with a +, which stands for everything. So if instead of a deviceID you put a + you'll listen to every device registered in the application.

If you only want to get a specific field you can write the name of the field after up/.

mosquitto_sub -h <Region>.thethings.network -t '+/devices/+/up/led' -u '<AppID>' -P '<AppKey>' -v

Sending Messages (down)

MQTT can also be used to send messages to TTN. For this you will have to address a specific device by its Device ID.

mosquitto_pub -h <Region>.thethings.network -t "<AppID>/devices/<DevID>/down" -u "<AppID>" -P "<AppKey>" -m "{""payload_fields"":{""led"":true}}"

Conclusion

That’s all from this article. If you have any questions or just want to chat with me, feel free to leave a comment below or contact me on social media. If you want to get continuous updates about my blog make sure to join my newsletter.