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The first step is to build an MQTT subscriber with Node-RED so we can receive the uplink stream.
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This is exactly what we did in the chapter about MQTT, so you will find many more details if you go
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back to the corresponding video.
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However, I will quickly do it one more time.
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We will need only two nodes the MQTT in node, so our subscriber and the debug node we'll always use it
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to check that everything works as expected.
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We connect them together and we can now configure the MQTT node.
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We have to set the broker address and its credentials and the topic.
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So we add a new MQTT broker called TTN.
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With the URL and the credentials, we can find this information on our network server documentation.
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In my case, I use TTN for this demonstration so I can find this information in the MQTT integration
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section.
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So that's the address, the username and the password that I need to generate.
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So the server address and in the security tab, the username and the password.
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Okay.
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And for the topic, I will subscribe to everything at the beginning.
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So I'm going to use the # wildcard.
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There is one more configuration for this node.
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It has nothing to do with MQTT, but if we want to have a nice output then it's better to select here:
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Parsed JSON object.
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Otherwise the output will be sent as text and it's not very convenient.
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I can also set a name TTN.
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Great.
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Let's deploy that.
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My subscriber is connected, which is a good news and I can see the log in the debug window.
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What I'm going to do before going forward is to change the topic.
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Because as we can see, there are more debug messages than uplink frames because I subscribe to all
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events on the network server, but the only one I'm interested in is the uplink event.
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And this is one: "v3/training-usmb@ttn/devices/device1-otaa/up"
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So I quickly modify the subscriber node with this topic.
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And I deploy my flow once again.
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This time when I transmit a frame, there is only one debug message.
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If I open the debug message, I can find everything I need in the uplink-
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message object: the payload,
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And further in the rx_metadata array, the RSSI.
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Fine.
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But there is one more thing that won't be very convenient here.
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It's that the payload is a string in base 64.
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Rather, I would rather have a number.
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I know that it's a temperature.
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So here I want a number representing that temperature.
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We have also done it in a previous video.
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The trick is to use the payload decoder of the network server.
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So we go on TTN, but of course you will find a similar payload decoder on all other network server.
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And in the uplink payload formatter section, then we can specify that the first byte.
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So byte zero is the data called temperature.
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If we do that, then now the LoRaWAN server will send a new object called decoded payload to our subscriber.
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And in this object we'll find our field temperature and its value.
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Okay, so first step is done.
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Now let's save this temperature on our side in the database.