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81 lines
2.4 KiB
81 lines
2.4 KiB
4 years ago
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# Control your nightlight over the Internet - Wio Terminal
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In this part of the lesson, you will send telemetry with light levels from your Wio Terminal to the MQTT broker.
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## Install the JSON Arduino libraries
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A popular way to send messages over MQTT is using JSON. There is an Arduino library for JSON that makes reading and writing JSON documents easier.
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### Task
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Install the Arduino JSON library.
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1. Open the nightlight project in VS Code.
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1. Add the following as an additional line to the `lib_deps` list in the `platformio.ini` file:
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```ini
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bblanchon/ArduinoJson @ 6.17.3
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```
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This imports [ArduinoJson](https://arduinojson.org), an Arduino JSON library.
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## Publish telemetry
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The next step is to create a JSON document with telemetry and send it to the MQTT broker.
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### Task
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Publish telemetry to the MQTT broker.
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1. Add the following code to the bottom of the `config.h` file to define the telemetry topic name for the MQTT broker:
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```cpp
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const string CLIENT_TELEMETRY_TOPIC = ID + "/telemetry";
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```
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The `CLIENT_TELEMETRY_TOPIC` is the topic the device will publish light levels to.
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1. Open the `main.cpp` file
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1. Add the following `#include` directive to the top of the file:
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```cpp
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#include <ArduinoJSON.h>
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```
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1. Add the following code inside the `loop` function, just before the `delay`:
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```cpp
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int light = analogRead(WIO_LIGHT);
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DynamicJsonDocument doc(1024);
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doc["light"] = light;
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string telemetry;
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JsonObject obj = doc.as<JsonObject>();
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serializeJson(obj, telemetry);
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Serial.print("Sending telemetry ");
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Serial.println(telemetry.c_str());
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client.publish(CLIENT_TELEMETRY_TOPIC.c_str(), telemetry.c_str());
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```
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This code reads the light level, and creates a JSON document using ArduinoJson containing this level. This is then serialized to a string and published on the telemetry MQTT topic by the MQTT client.
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1. Upload the code to your Wio Terminal, and use the Serial Monitor to see the light levels being sent to the MQTT broker.
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```output
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Connecting to WiFi..
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Connected!
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Attempting MQTT connection...connected
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Sending telemetry {"light":652}
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Sending telemetry {"light":612}
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Sending telemetry {"light":583}
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```
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> 💁 You can find this code in the [code-telemetry/wio-terminal](code-telemetry/wio-terminal) folder.
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😀 You have successfully sent telemetry from your device.
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