Your First Sensor

Start where you left off

In the previous lesson, you pulled down the SDK and connect your device. Let's start with that code base.

Add a timer mechanism to your loop

Look at your src/main.cpp and fine the loop() function.

void loop() {

    controller.loop();

    if (mqtt.is_connected) {

        // do something
        
    }

}

Modify your loop to run some code every 8 seconds (and maybe delete some of those extra lines):

unsigned long timer = millis();
            
void loop() {
    controller.loop();
    if (mqtt.is_connected) {
        if (millis() - timer > 8000) {
            // do something
        }
    }
}

Generate a mock temperature value

Replace // do something with

float temperature = 68.0 + random(-30, 30) / 10.0;
mqtt.publish("~/~/numb/temperature/temp1", temperature);
timer = millis();

Confirm that your device is sending

Upload your code, and check the serial monitor. You should see something like this:

  booting...

	existing deviceID: a8f3k2m1

	wifi connecting...
	wifi connected...

	mqtt connecting...
	mqtt connected...

	sending: larry/a8f3k2m1/numb/temperature/temp    68.30
	sending: larry/a8f3k2m1/numb/temperature/temp    67.50
	sending: larry/a8f3k2m1/numb/temperature/temp    69.10

See it on the dashboard

Open app.ohioiot.com and go to the Data screen. Within a few seconds you should see a graph labeled "Temperature" with a line called "temp1" that updates in real time.

When you have several data points publishing to a graph, it can be slightly chaotic to see the different data points arriving at different times. To smooth out the visualization, numerical data points, by default, are aggregated and published together on a 10-second interval. So, you will notice that, although you are sending data every 8 seconds, the graph is updating every 10, showing the last value that was published.

If you would like to change or turn off this aggregation interval, go to the Settings tab, and open "My Data". There, you can change the aggregation interval for both numerical data and boolean data.