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69 lines
3.3 KiB
69 lines
3.3 KiB
3 years ago
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# Publish temperature - Wio Terminal
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In this part of the lesson, you will publish the temperature values detected by the Wio Terminal over MQTT so they can be used later to calculate GDD.
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## Publish the temperature
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Once the temperature has been read, it can be published over MQTT to some 'server' code that will read the values, and store them ready to be used for a GDD calculation. Microcontrollers don't read the time from the Internet and track the time with a real-time clock out of the box, the device needs to be programmed to do this, assuming it has the necessary hardware.
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To simplify things for this lesson, the time won't be sent with the sensor data, instead it can be added by the server code later when it receives the messages.
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### Task
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Program the device to publish the temperature data.
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1. Open the `temperature-sensor` Wio Terminal project
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1. Repeat the steps you did in lesson 4 to connect to MQTT and send telemetry, You will be using the same public Mosquitto broker.
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The steps for this are:
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- Add the Seeed WiFi and MQTT libraries to the `.ini` file
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- Add the config file and code to connect to WiFi
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- Add the code to connect to the MQTT broker
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- Add the code to publish telemetry
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> ⚠️ Refer to the [instructions for connecting to MQTT](../../../1-getting-started/lessons/4-connect-internet/wio-terminal-mqtt.md) and the [instructions for sending telemetry](../../../1-getting-started/lessons/4-connect-internet/wio-terminal-telemetry.md) from lesson 4 if needed.
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1. Make sure the `CLIENT_NAME` in the `config.h` header file reflects this project:
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```cpp
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const string CLIENT_NAME = ID + "temperature_sensor_client";
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```
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1. For the telemetry, instead of sending a light value, send the temperature value read from the DHT sensor in a property on the JSON document called `temperature` by changing the `loop` function in `main.cpp`:
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```cpp
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float temp_hum_val[2] = {0};
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dht.readTempAndHumidity(temp_hum_val);
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DynamicJsonDocument doc(1024);
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doc["temperature"] = temp_hum_val[1];
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```
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1. The temperature value doesn't need to be read very often - it won't change much in a short space of time, so set the `delay` in the `loop` function to 10 minutes:
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```cpp
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delay(10 * 60 * 1000);
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```
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> 💁 The `delay` function takes the time in milliseconds, so to make it easier to read the value is passed as the result of a calculation. 1,000ms in a second, 60s in a minute, so 10 x (60s in a minute) x (1000ms in a second) gives a 10 minute delay.
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1. Upload this to your Wio Terminal, and use the serial monitor to see the temperature being sent to the MQTT broker.
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```output
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--- Available filters and text transformations: colorize, debug, default, direct, hexlify, log2file, nocontrol, printable, send_on_enter, time
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--- More details at http://bit.ly/pio-monitor-filters
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--- Miniterm on /dev/cu.usbmodem1201 9600,8,N,1 ---
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--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
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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 {"temperature":25}
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Sending telemetry {"temperature":25}
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```
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> 💁 You can find this code in the [code-publish-temperature/wio-terminal](code-publish-temperature/wio-terminal) folder.
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😀 You have successfully published the temperature as telemetry from your device.
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