Page 125 - Programming the Photon Getting Started With the Internet of Things

<br>
<input type="radio" name="args" value="off">Turn the LED off.

<br>
<br>
<input type="submit" value="Do it!">
</form>
</center>

Edit the code in the HTML document so that “your device id goes here” is your actual
ID and “your access token” is your access token. You can open up a standard text editor to

save this code as an .html document so that you can open it in your Web browser. Go
ahead and open the .html document in your browser—you should be presented with a
simple form that allows you to select either on or off. When you click the Do it! button
you are posting information to the URL https://api.particle.io/v1/devices/your-device-ID-

goes-here/led?access_token=your-access-token-goes-here. The information you are giving
is the argument value ON or OFF. This parses through the spark.function that we
registered. When you send the information, you will also get some information back from
the page once sent that gives the status of your deice and lets you know that the post was

successfully sent to the Photon board. If you want to go back, just click the back button in
your browser.

Reading Values over the Internet

Now that we understand how to send commands to the board to turn things on or off, we
also need to learn how to read values from sensors such as temperature, humidity, or light.
We can refer back to Chapter 5 where we used the analog pins on the Photon board to read
sensor information—these pins are labeled A0–A5. We can only connect components to

the analog pin, where we know that the voltage can vary between 0 V and 3.3 V; any
higher voltages will damage the Photon board as well as the component itself. The
principle of reading anything from the analog pins is quite simple; take a look at the
following code:

int getvalue = 0;
int analogPin = A0;

void setup() {
Spark.variable("analog", &getvalue, INT);

}

void loop() {
getvalue = analogRead(analogPin);
}