Page 139 - Programming the Photon Getting Started With the Internet of Things
P. 139

void setup()
        {

            Spark.variable("cm", &cm, DOUBLE);
            Spark.variable("inches", &inches, DOUBLE);
        }



        void loop()
        {
            cm = rangefinder.getDistanceCM();
            inches = rangefinder.getDistanceInch();

            delay(100);
        }

             In the first line we can import the HC_SR04 library so we can use all the functions to get

        the  distance  from  the  sensor.  The  library  can  be  found  in  the  Particle  build  IDE  by
        searching for “HC SR04” and importing it into your program. For this experiment we are
        going to provide two options to measure in both centimeters and inches, which we define
        as double variables.


        double cm = 0.0;

        double inches = 0.0;

             We also have created two spark variables for both centimeters and inches so we can

        call the values from our webpage for whichever one we require. The loop function keeps
        checking the distance every tenth of a second to update the value accurately. Our HTML
        page will be similar to the previous experiment, with a few minor changes:


        <html>
        <head>

        <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.j
        s" type="text/javascript" charset="utf-8"></script>
        <script src="raphael.2.1.0.min.js"></script>
        <script src="justgage.1.0.1.min.js"></script>





        <script>
        var accessToken = "you access token here";

        var deviceID = "you device id here"


        var distance_url = "https://api.spark.io/v1/devices/" + deviceID + "/distan
        ceCM";



        function callbackDistance(data, status){
                   if (status == "success") {
   134   135   136   137   138   139   140   141   142   143   144