Connect to The Things Network

This guide provides step-by-step instructions for connecting Hardwario LoRa devices to The Things Network (TTN). It covers the installation of a LoRaWAN gateway, configuration of a Hardwario LoRa device for TTN, connecting the device to TTN, and uploading a payload formatter to TTN.

Note

This guide applies to all firmware in the HARDWARIO Playground with the prefix twr-lora. The examples are based on TTN console v3.16.0. The guide was originally written in November 2021 and uses the AT command interface and TTN console available at that time.

Background

The Things Network

The Things Network (TTN) is a global community-maintained LoRaWAN network. TTN infrastructure is operated by volunteers. The network is open, i.e., anybody can connect new LoRa devices to the network via existing gateways. At the highest level, the network is organized into separate geographical clusters: Europe, North America, Australia. Gateways and devices are associated with a particular cluster based on their location. The gateways within each cluster are organized into communities. A community is a group of volunteers in a specific region, e.g., city or country, who operate LoRa gateways.

Hardwario LoRa Module

The Hardwario LoRa module is compatible with TTN. Thus, you can connect your Hardwario device to TTN and access its measurements through any of the APIs and protocols supported by the network, including (but not limited to) HTTP push (webhooks), MQTT, AWS IoT, Azure IoT. If your LoRa devices are installed in an area that is already covered by an existing TTN gateway, all you need to do is register your LoRa device to TTN. If your area is not covered, consider purchasing a small LoRa gateway to install yourself. There are several affordable and easy to install LoRa gateways on the market such as The Things Indoor LoRaWAN Wi-Fi Gateway.

Install LoRa Gateway for TTN

Note

If you have no TTN gateway nearby, you may need to install your own. The process is quick and easy. This section provides a step-by-step guide to connecting The Things Indoor LoRaWAN Wi-Fi Gateway to TTN. For more detailed instructions please refer to the official documentation.

Locate the sticker (with a QR code) on the back of the gateway. Write down the 12-character alphanumeric string (gateway ID). Convert the ID to a gateway EUI by inserting the string FFFE between the 6th and 7th character. For example, if your gateway ID is 58A0CB801AD9, your gateway EUI will be 58A0CBFFFE801AD9.

Write down the Wi-Fi password printed on the same sticker. It will be needed later.

Optionally, reset the gateway to factory defaults. Press and hold the reset button at the bottom of the gateway for 5 seconds, or until the LED starts rapidly blinking red-green.

Press and hold the setup button at the top of the gateway for 10 seconds, or until the LED starts blinking red. The gateway creates a temporary Wi-Fi network called ​​MiniHub-XXXXXX, where XXXXXX is the last 6 characters of the gateway ID recorded earlier. Connect to the temporary Wi-Fi network using the Wi-Fi password noted earlier.

Once connected, navigate in your browser to http://192.168.4.1. The browser should load the gateway’s setup page. Select the name of your Wi-Fi network from the list of scanned Wi-Fi networks by clicking on the + button on the line:

When prompted, enter the password for the Wi-Fi network. Click the button “Save & Reboot”. The gateway will blink green until it successfully connects to the configured Wi-Fi network. Once the LED turns solid green, the gateway is connected to Wi-Fi and to TTN.

Login to the TTN console and select a cluster from the left hand side menu. On the next screen, click on “Go to gateways”. On the next screen, click on the button “Claim gateway”. You will be presented with the following form:

If not auto-filled, enter your TTN account username into the field “Collaborator ID”. Enter the gateway EUI created earlier into the field “Gateway EUI”. Enter the Wi-Fi password from the sticker on the gateway into the field “Claim authentication code”. Set a unique name for the gateway in “Gateway ID” and select the appropriate frequency plan for your region in the dropdown “Frequency plan”. Click on the button “Claim gateway” to complete the process. You should be then redirected to the overview page for the gateway.

Connect Hardwario LoRa Device to TTN

Connecting a Hardwario LoRa device to TTN consists of the following steps:

  1. Create a TTN application (optional if you already have one)

  2. Configure Hardwario LoRa device for TTN

  3. Register the device in TTN

  4. Execute the OTAA join operation on the device

  5. Upload a payload formatter to TTN (optional)

TTN-related steps are performed in the web-based TTN console. LoRa device configuration is performed via the AT command interface provided by the Hardwario Core module over its USB-serial interface.

Create TTN Application

Tip

You can skip this section if you already have a TTN application.

A TTN application is a logical group of related LoRa devices and associated data, e.g., configuration, payload formaters, keys, and stored data.

Log in to the TTN console, select the appropriate cluster from the left hand side menu, and click on “Go to applications”. Click on the button “Add application” to create a new application. Fill out the form with application name and unique application ID and then click on the button “Create application”. You will be redirected to the overview page for the newly created application that looks like this:

Configure Hardwario LoRa Device for TTN

Make sure you have a recent firmware with LoRa module support loaded in the device. If not, follow the instructions on the Hardwario developer website to load the right firmware into the device.

Connect to Device

Connect the Hardwario device to your computer with a USB cable. We need to find out the filename assigned to the device’s serial interface by the Linux kernel. There are several ways to do this. If you have the Hardwario firmware flashing tool installed, run bcf devices -v to see a list of all connected devices:

bcf devices -v
/dev/ttyUSB0
    desc: USB-3003 - USB-3003
    hwid: USB VID:PID=0403:6001 SER=DVAPPPU0 LOCATION=1-1
/dev/ttyUSB1
    desc: (none) - (none)
    hwid: USB VID:PID=0403:6015 SER=2416968042 LOCATION=1-4

Select the filename corresponding to your device’s serial number (SER=). In the above example, there is one Hardwario Core module with serial number 2416968042 and its filename is /dev/ttyUSB1.

Next, use picocom, minicom, screen or similar terminal emulator to connect to the device. Serial port configuration is 115200 8N1 (one start bit, eight bits, no parity). The Core module uses CRFL (\r\n) as the end-of-line delimiter. With picocom you can use the the following command line parameters:

picocom -b 115200 --omap crcrlf --echo /dev/ttyUSB1

In the following sections, we will be using the AT command interface supported by all Hardwario twr-lora firmware. If you are unfamiliar with AT commands, please read the guide to LoRa AT commands first.

Reset to Factory Defaults

Note

This step is optional but highly recommended. Pre-existing LoRa module settings and state are a suprisingly common source of problems during device activation.

The Hardwario LoRa module has persistent internal memory that is used to store modem settings. If you are unsure what state your LoRa module is in, e.g., whether it has any previous saved settings or configuration, consider resetting the module to factory defaults.

To reset the LoRa module, send the AT command AT$FRESET. This command will reset the LoRa module to factory defaults. Once the module has responded with “OK”, reboot the Core module by sending AT$REBOOT:

AT$FRESET
OK
AT$REBOOT

Configure LoRa Modem

Configure the Hardwario LoRa module for TTN. First, select the right frequency band based on your region:

AT$BAND=8

The value 8 represents the U.S. 915 MHz band. Note: You can use the command AT$HELP to see the full list of supported values:

...
AT$BAND 0:AS923, 1:AU915, 5:EU868, 6:KR920, 7:IN865, 8:US915
...

TTN is a public network, so we need to configure the LoRa module to connect to a public network:

AT$NWK=1

Finally, we need to select the activation method. LoRaWAN supports two activation methods: Over the Air Activation (OTAA) and Activation by Personalization (ABP). The OTAA method is more convenient and generally recommended. If you are reading this guide, OTAA is what you probably want to use. Send the following command to activate the OTAA mode:

AT$MODE=1

Note

AT$BAND and AT$NWK settings are persistent and only need to be configured once after the device has been reset to factory defaults. The AT$MODE setting is temporary and will be reset to 0 (ABP) on device reboot. Thus, you should issue AT$MODE=1 before every AT$JOIN (discussed below).

Register Hardwario LoRa Device in TTN

First, use the AT command interface to obtain a few values from the Hardwario LoRa module that will be needed to register the device in TTN:

AT$DEVEUI?
$DEVEUI: 3632313691398608
OK

AT$APPEUI?
$APPEUI: 0101010101010101
OK

AT$APPKEY?
$APPKEY: B2E7511628AED2A6ABF7158809CF4F3C
OK

Note the three values. DevEUI is the unique identifier (address) of your device. AppEUI (also known as JoinEUI) is a string that identifies the join server during OTAA activation. AppKey is the root AES-128 secret key unique to the device. This key will be used to derive various session keys during the OTAA process.

Switch to the TTN console. Navigate to the overview screen for your newly created TTN application. Select “End devices” from the left hand side menu. Click the button “Add end device”. You will be redirected to the following screen:

The Hardwario LoRa module is not included in the TTN LoRaWAN device repository. Thus, we need to register the device manually. Select the tab “Manually”:

In the dropdown “Frequency plan” select the appropriate frequency plan for your region. Most likely, this will be one of the plans marked with “(used by TTN)”. The frequency plan must match the frequency plan that you configured in the Hardwario LoRa module with the command AT$BAND.

In the dropdown “LoRaWAN version” select “MAC V1.0.2”. Select “PHY v1.0.2 REV B” in the dropdown “Regional Parameters version”. This is the most recent MAC version supported by the Hardwario LoRa module.

Paste the DevEUI, AppEUI, and AppKey values obtained through the AT command interface earlier into the corresponding form fields. The completely filled out form should look like this:

Click on “Register end device” to complete the registration process.

Execute OTAA Join

Now that your LoRa module is properly configured and registered in TTN, you can execute the OTAA join operation. During the join, the LoRa module needs to be able to communicate with a LoRa gateway, so make sure it has an antenna connected and it is located in a place with a good LoRa signal from the gateway. Send AT$JOIN to the device to initiate the join:

AT$JOIN
OK

The device responds with an “OK” which indicates that the command was accepted and the operation is in progress. After a while, you should receive either “$JOIN_OK” or “$JOIN_ERROR” in the terminal. The former indicates that your device has successfully joined TTN and is ready to communicate. The latter indicates that the join failed and needs to be repeated. The culprit is commonly incorrect LoRa module settings, e.g., mismatched DevEUI, AppEui, or AppKey. If your joins fail repeatedly, try resetting the LoRa modem to factory defaults, reboot the device, and follow the configuration steps mentioned earlier.

Warning

All LoRa module settings as well as the keys generated during OTAA join are stored in the internal flash memory of the LoRa module. If you replace the LoRa module, you will have to configure and join the device to TTN again.

Also, connecting a previously joined LoRa module to a new Core module with a different firmware can be problematic if the firmware uses an incompatible payload format. Since the identity of the device (from TTN point of view) is tied to the LoRa module and not to the Core module, TTN may apply incorrect (old) payload formatters to the new device.

For the above reasons, we recommend to always reset the LoRa module to factory defaults with AT$FRESET if the module is being replaced or reconnected to another Core module.

Upload Payload Formatter

LoRa devices generally send data (sensor measurements) encoded in binary form to keep messages short and to save air time. Without knowing how the data from a particular device is encoded, TTN would have to submit the data in the original binary format to HTTP webhooks or MQTT clients. Internally, TTN must also encode binary data in Base64 to be able to pass it around in JSON messages. Dealing with such binary data is inconvenient and places extra burden on application developers. For that reason, TTN provides a feature called payload formatters which allows TTN to decode arbitrary binary data into a JSON value more suitable for HTTP webhooks or MQTT.

Whenever TTN receives a LoRa message from a device, it checks whether a payload formatter function exists either for the device, or for the TTN application the device is part of. If a payload formatter exists, TTN passes the binary data to the formatter function. The return value of the function, usually in the form of a JSON object, is then provided to applications over HTTP webhooks or MQTT. For example, a payload formatter could convert the value ASAA+Q== to the following JSON object:

{
    "header": 1,
    "temperature": 24.9,
    "voltage": 3.2
}

A payload formatter function can be defined for a particular LoRa device, or for the entire TTN application. Application payload formatters are applied to all devices within the application. Device-specific payload formatters take precedence over application payload formatters.

To define a new application payload formatter, navigate to the overview screen for your TTN application. Select “Payload formatters” and “Uplink” in the left hand side menu. In the dropdown “Formatter type” select “JavaScript”. The TTN console will present you with a JavaScript formatter template that looks as follows:

Whenever a LoRa device within the application sends a message to TTN, the function decodeUplink will be invoked with the LoRa message in the parameter input. The property bytes contains the binary payload generated by the device, for example, the state of various sensors. The formatter function converts the binary payload into a JavaScript object and the object is returned in the property data.

For firmware created by Hardwario, you can often find a default payload formatter implementation in the Github repository for the firmware. For example, a payload formatter for the firmware twr-lora-climate-monitor can be found here.

Copy the payload formatter JavaScript program and paste it at the beginning of the “Formatter parameter” field shown above. Then invoke the function Decoder with input.bytes as an argument and assign the returned value to the property data. The whole JavaScript program should look like this:

function Decoder(bytes, port) {
    // Decode an uplink message from a buffer
    var header = bytes[0];
    var voltage = bytes[1] / 10.0;
    var orientation = bytes[2];
    var temperature = ((bytes[3] << 8) | bytes[4]) / 10.0;
    var humidity = bytes[5] / 2;
    var illuminance = ((bytes[6] << 8) | bytes[7]);
    var pressure = ((bytes[8] << 8) | bytes[9]) * 2.0;

    // (array) of bytes to an object of fields.
    var decoded = {
        header: header,
        voltage: voltage,
        orientation: orientation,
        temperature: temperature,
        humidity: humidity,
        illuminance: illuminance,
        pressure: pressure

    };

    return decoded;
}

function decodeUplink(input) {
    return {
        data: Decoder(input.bytes),
        warnings: [],
        errors: []
    };
}

In LoRa, message payload is encrypted with the application session key (AppSKey). To apply the payload formatter, the TTN network must have access to AppSKey. This is generally the case with LoRa devices added with the OTAA method where AppSKey is generated by the network server.

For devices added via the ABP method that is not necessarily the case. To use payload formatters with ABP devices, you need to configure the AppSKey into TTN manually if you wish to use the feature. Otherwise, your HTTP or MQTT endpoints will be given encrypted message payload and you need to decrypt and parse the data yourself.