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LED - Controlling LED via WebSocket

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  • LED - Controlling LED via WebSocket


    Tutorial Video



    Hardware
    • PHPoC Blue (+ USB WLAN) or PHPoC Black (+ Ethernet cable)
    • Micro USB to USB Cable (to upload source code to PHPoC Device)


    About Built-in LED

    There are some LEDs are built-in on PHPoC board. This helps user quickly get started without wiring anything. These LED were already connected to IO pin of PHPoC device.

    How to control built-in LED:
    • These LEDs are turned ON by setting IO pin of PHPoC device to LOW (0 V).
    • These LEDs are turned OFF by setting IO pin of PHPoC device to HIGH (3.3 V).


    Quick Steps

    Source code of this example is a part of PHPoC Support Packet (PSP). You need to:
    • Download PHPoC Support Package.
    • Upload example\p4s\05.html5_graphics\01.uio_ob_led to PHPoC Blue/Black.
    • Configure network parameters (e.g. WiFi SSID, password, IP address ...).
    • Click "Run" button on PHPoC Debugger.
    • Access webpage on PHPoC using Web Browser on your PC or smart phone (See How To).
    If you use PHPoC for the first time, see How To Use PSP.


    Source Code

    Source files includes:
    • init.php: this file is run when PHPoC system is powered or reset. It is used to specify which file is run is system loop.
    • task0.php: this file is run in system loop of PHPoC devices. It acts as WebSocket server and also interacts with built-in LED.
    • index.php: this file contains source code of web page.It is only run in response to request from Web Browser. It contains webpage (user interface) and acts WebSocket client.
    • button_pop.png: Image.
    • button_push.png: Image.

    index.php

    [Full Code]
    PHP Code:
    <!DOCTYPE html>
    <html>
    <head>
    <title>PHPoC / <?echo system("uname -i")?></title>
    <meta name="viewport" content="width=device-width, initial-scale=0.7">
    <style> body { text-align: center; } </style>
    <script>
    var canvas_width = 95;
    var canvas_height = 95;
    var ws;
    function init()
    {
     var button = document.getElementById("button");

     button.width = canvas_width;
     button.height = canvas_height;

     button.addEventListener("touchstart", mouse_down);
     button.addEventListener("touchend", mouse_up);
     button.addEventListener("touchcancel", mouse_up);
     button.addEventListener("mousedown", mouse_down);
     button.addEventListener("mouseup", mouse_up);
     button.addEventListener("mouseout", mouse_up);

     update_button(1);

     ws = new WebSocket("ws://<?echo _SERVER("HTTP_HOST")?>/ob_led", "csv.phpoc");
     document.getElementById("ws_state").innerHTML = "CONNECTING";

     ws.onopen  = function(){ document.getElementById("ws_state").innerHTML = "OPEN" };
     ws.onclose = function(){ document.getElementById("ws_state").innerHTML = "CLOSED"};
     ws.onerror = function(){ alert("websocket error " + this.url) };

     ws.onmessage = ws_onmessage;
    }
    function ws_onmessage(e_msg)
    {
     e_msg = e_msg || window.event; // MessageEvent

     alert("msg : " + e_msg.data);
    }
    function update_button(state)
    {
     var button = document.getElementById("button");

     if(state)
      button.style.backgroundImage = "url('/button_pop.png')";
     else
      button.style.backgroundImage = "url('/button_push.png')";
    }
    function mouse_down()
    {
     if(ws.readyState == 1)
      ws.send("0\r\n");

     update_button(0);

     event.preventDefault();
    }
    function mouse_up()
    {
     if(ws.readyState == 1)
      ws.send("1\r\n");

     update_button(1);
    }
    window.onload = init;
    </script>
    </head>
    <body>

    <h2>
    UIO / On-Board User LED<br>

    <br>

    <canvas id="button"></canvas>

    <p>
    WebSocket : <span id="ws_state">CLOSED</span><br>
    <!--
    ADC : <span id="debug"></span><br>
    -->
    </p>

    </h2>

    </body>
    </html>



    [Explanation]

    Source code of index.php file is composed of HTML, CSS, JavaScript and PHPoC code.

    PHPoC code is interpreted on on PHPoC device.

    PHPoC code may add/update the content of HTML, CSS or JavaScript code. Once PHPoC code is interpreted in PHPoC, the remaining code is client-side code and it is returned to Web Browser. Web Browser receives this code and interpret it to display the webpage.
    • HTML: describes the structure of Web pages
    • CSS: describes how HTML elements are to be displayed
    • JavaScript: This code:
      - Handle click/touch event from user on Webpage,
      - The controlling state of built-in LED is ON and OFF if button is pressed or released, respectively,
      - Send ON/OFF state of built-in LED to PHPoC device via WebSocket
      - Update Graphic UI: change background image with respect to the pressed/released state

    init.php

    This file is run when PHPoC system is powered or reset. It is used to specify that task0.php is run is system loop.
    PHP Code:
    <?php

    system
    ("php task0.php");

    ?>



    task0.php

    [Full Code]
    PHP Code:
    <?php

    if(_SERVER("REQUEST_METHOD"))
     exit; 
    // avoid php execution via http request

    include "/lib/sd_340.php";
    include 
    "/lib/sn_tcp_ws.php";

    define("OUT_PIN"30);

    uio_setup(0OUT_PIN"out high");
    ws_setup(0"ob_led""csv.phpoc");

    $rwbuf "";

    while(
    1)
    {
     if(
    ws_state(0) == TCP_CONNECTED)
     {
      
    $rlen ws_read_line(0$rwbuf);

      if(
    $rlen)
       
    uio_out(0OUT_PIN, (int)$rwbuf);
     }
    }

    ?>



    [Explanation]

    Source code of this file does:
    • Setup IO pin to output mode and initialize IO pin state to HIGH (LED is off).
    • Setup and initialize WebSocket.
    In infinite loop:
    • Receive data (ON/OFF state )from Web Browser via WebSocket.
    • Control built-in LED by changing state of IO pin according to the received data.
    For detail explanation, see How to Control Devices via WebSocket




    See Also

    Other Resources
    Last edited by support; 02-09-2018, 08:59 AM.
      Posting comments is disabled.

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