Two Gauge Arduino Web Server

Created on: 30 July 2014

The question has been asked on the blog entry for the Arduino Ethernet Shield Web Server Tutorial how to go about adding a second gauge on a web page.

Part 15 of the web server tutorial displays a single gauge. This tutorial shows how to add a second gauge to a web page to display the input of a second analog channel on the Arduino.

The video below shows the two gauges working when two potentiometers are connected to analog inputs A2 and A3 of an Arduino Uno and Arduino Ethernet Shield.

The actual web page is hosted on the SD card of the Arduino Ethernet Shield.

Can't see the video? View on YouTube →


Web Page Changes

The web page from part 15 of the web server tutorial is modified as shown below.

<!DOCTYPE html>
<html>
    <head>
        <title>Arduino Ajax Two Dial</title>
        <script>
        var data_val = 0;
        var data_val2 = 0;
<!-- Gauge Code Starts -->
var Gauge=function(b){function l(a,b){for(var c in b)"object"==typeof b[c]&&"[object Array]"!==Object.prototype.toString.call(b[c])&&"renderTo"!=c?("object"!=typeof a[c]&&(a[c]={}),l(a[c],b[c])):a[c]=b[c]}function q(){z.width=b.width;z.height=b.height;A=z.cloneNode(!0);B=A.getContext("2d");C=z.width;D=z.height;t=C/2;u=D/2;f=t<u?t:u;A.i8d=!1;B.translate(t,u);B.save();a.translate(t,u);a.save()}function v(a){var b=new Date;G=setInterval(function(){var c=(new Date-b)/a.duration;1<c&&(c=1);var f=("function"==
typeof a.delta?a.delta:M[a.delta])(c);a.step(f);1==c&&clearInterval(G)},a.delay||10)}function k(){G&&clearInterval(G);var a=I-n,h=n,c=b.animation;v({delay:c.delay,duration:c.duration,delta:c.fn,step:function(b){n=parseFloat(h)+a*b;E.draw()}})}function e(a){return a*Math.PI/180}function g(b,h,c){c=a.createLinearGradient(0,0,0,c);c.addColorStop(0,b);c.addColorStop(1,h);return c}function p(){var m=93*(f/100),h=f-m,c=91*(f/100),e=88*(f/100),d=85*(f/100);a.save();b.glow&&(a.shadowBlur=h,a.shadowColor=
"rgba(0, 0, 0, 0.5)");a.beginPath();a.arc(0,0,m,0,2*Math.PI,!0);a.fillStyle=g("#ddd","#aaa",m);a.fill();a.restore();a.beginPath();a.arc(0,0,c,0,2*Math.PI,!0);a.fillStyle=g("#fafafa","#ccc",c);a.fill();a.beginPath();a.arc(0,0,e,0,2*Math.PI,!0);a.fillStyle=g("#eee","#f0f0f0",e);a.fill();a.beginPath();a.arc(0,0,d,0,2*Math.PI,!0);a.fillStyle=b.colors.plate;a.fill();a.save()}function w(a){var h=!1;a=0===b.majorTicksFormat.dec?Math.round(a).toString():a.toFixed(b.majorTicksFormat.dec);return 1<b.majorTicksFormat["int"]?
(h=-1<a.indexOf("."),-1<a.indexOf("-")?"-"+(b.majorTicksFormat["int"]+b.majorTicksFormat.dec+2+(h?1:0)-a.length)+a.replace("-",""):""+(b.majorTicksFormat["int"]+b.majorTicksFormat.dec+1+(h?1:0)-a.length)+a):a}function d(){var m=81*(f/100);a.lineWidth=2;a.strokeStyle=b.colors.majorTicks;a.save();if(0===b.majorTicks.length){for(var h=(b.maxValue-b.minValue)/5,c=0;5>c;c++)b.majorTicks.push(w(b.minValue+h*c));b.majorTicks.push(w(b.maxValue))}for(c=0;c<b.majorTicks.length;++c)a.rotate(e(45+c*(270/(b.majorTicks.length-
1)))),a.beginPath(),a.moveTo(0,m),a.lineTo(0,m-15*(f/100)),a.stroke(),a.restore(),a.save();b.strokeTicks&&(a.rotate(e(90)),a.beginPath(),a.arc(0,0,m,e(45),e(315),!1),a.stroke(),a.restore(),a.save())}function J(){var m=81*(f/100);a.lineWidth=1;a.strokeStyle=b.colors.minorTicks;a.save();for(var h=b.minorTicks*(b.majorTicks.length-1),c=0;c<h;++c)a.rotate(e(45+c*(270/h))),a.beginPath(),a.moveTo(0,m),a.lineTo(0,m-7.5*(f/100)),a.stroke(),a.restore(),a.save()}function s(){for(var m=55*(f/100),h=0;h<b.majorTicks.length;++h){var c=
F(m,e(45+h*(270/(b.majorTicks.length-1))));a.font=20*(f/200)+"px Arial";a.fillStyle=b.colors.numbers;a.lineWidth=0;a.textAlign="center";a.fillText(b.majorTicks[h],c.x,c.y+3)}}function x(a){var h=b.valueFormat.dec,c=b.valueFormat["int"];a=parseFloat(a);var f=0>a;a=Math.abs(a);if(0<h){a=a.toFixed(h).toString().split(".");h=0;for(c-=a[0].length;h<c;++h)a[0]="0"+a[0];a=(f?"-":"")+a[0]+"."+a[1]}else{a=Math.round(a).toString();h=0;for(c-=a.length;h<c;++h)a="0"+a;a=(f?"-":"")+a}return a}function F(a,b){var c=
Math.sin(b),f=Math.cos(b);return{x:0*f-a*c,y:0*c+a*f}}function N(){a.save();for(var m=81*(f/100),h=m-15*(f/100),c=0,g=b.highlights.length;c<g;c++){var d=b.highlights[c],r=(b.maxValue-b.minValue)/270,k=e(45+(d.from-b.minValue)/r),r=e(45+(d.to-b.minValue)/r);a.beginPath();a.rotate(e(90));a.arc(0,0,m,k,r,!1);a.restore();a.save();var l=F(h,k),p=F(m,k);a.moveTo(l.x,l.y);a.lineTo(p.x,p.y);var p=F(m,r),n=F(h,r);a.lineTo(p.x,p.y);a.lineTo(n.x,n.y);a.lineTo(l.x,l.y);a.closePath();a.fillStyle=d.color;a.fill();
a.beginPath();a.rotate(e(90));a.arc(0,0,h,k-0.2,r+0.2,!1);a.restore();a.closePath();a.fillStyle=b.colors.plate;a.fill();a.save()}}function K(){var m=12*(f/100),h=8*(f/100),c=77*(f/100),d=20*(f/100),k=4*(f/100),r=2*(f/100),l=function(){a.shadowOffsetX=2;a.shadowOffsetY=2;a.shadowBlur=10;a.shadowColor="rgba(188, 143, 143, 0.45)"};l();a.save();n=0>n?Math.abs(b.minValue-n):0<b.minValue?n-b.minValue:Math.abs(b.minValue)+n;a.rotate(e(45+n/((b.maxValue-b.minValue)/270)));a.beginPath();a.moveTo(-r,-d);a.lineTo(-k,
0);a.lineTo(-1,c);a.lineTo(1,c);a.lineTo(k,0);a.lineTo(r,-d);a.closePath();a.fillStyle=g(b.colors.needle.start,b.colors.needle.end,c-d);a.fill();a.beginPath();a.lineTo(-0.5,c);a.lineTo(-1,c);a.lineTo(-k,0);a.lineTo(-r,-d);a.lineTo(r/2-2,-d);a.closePath();a.fillStyle="rgba(255, 255, 255, 0.2)";a.fill();a.restore();l();a.beginPath();a.arc(0,0,m,0,2*Math.PI,!0);a.fillStyle=g("#f0f0f0","#ccc",m);a.fill();a.restore();a.beginPath();a.arc(0,0,h,0,2*Math.PI,!0);a.fillStyle=g("#e8e8e8","#f5f5f5",h);a.fill()}
function L(){a.save();a.font=40*(f/200)+"px Led";var b=x(y),h=a.measureText("-"+x(0)).width,c=f-33*(f/100),g=0.12*f;a.save();var d=-h/2-0.025*f,e=c-g-0.04*f,h=h+0.05*f,g=g+0.07*f,k=0.025*f;a.beginPath();a.moveTo(d+k,e);a.lineTo(d+h-k,e);a.quadraticCurveTo(d+h,e,d+h,e+k);a.lineTo(d+h,e+g-k);a.quadraticCurveTo(d+h,e+g,d+h-k,e+g);a.lineTo(d+k,e+g);a.quadraticCurveTo(d,e+g,d,e+g-k);a.lineTo(d,e+k);a.quadraticCurveTo(d,e,d+k,e);a.closePath();d=a.createRadialGradient(0,c-0.12*f-0.025*f+(0.12*f+0.045*f)/
2,f/10,0,c-0.12*f-0.025*f+(0.12*f+0.045*f)/2,f/5);d.addColorStop(0,"#888");d.addColorStop(1,"#666");a.strokeStyle=d;a.lineWidth=0.05*f;a.stroke();a.shadowBlur=0.012*f;a.shadowColor="rgba(0, 0, 0, 1)";a.fillStyle="#babab2";a.fill();a.restore();a.shadowOffsetX=0.004*f;a.shadowOffsetY=0.004*f;a.shadowBlur=0.012*f;a.shadowColor="rgba(0, 0, 0, 0.3)";a.fillStyle="#444";a.textAlign="center";a.fillText(b,-0,c);a.restore()}Gauge.Collection.push(this);this.config={renderTo:null,width:200,height:200,title:!1,
maxValue:100,minValue:0,majorTicks:[],minorTicks:10,strokeTicks:!0,units:!1,valueFormat:{"int":3,dec:2},majorTicksFormat:{"int":1,dec:0},glow:!0,animation:{delay:10,duration:250,fn:"cycle"},colors:{plate:"#fff",majorTicks:"#444",minorTicks:"#666",title:"#888",units:"#888",numbers:"#444",needle:{start:"rgba(240, 128, 128, 1)",end:"rgba(255, 160, 122, .9)"}},highlights:[{from:20,to:60,color:"#eee"},{from:60,to:80,color:"#ccc"},{from:80,to:100,color:"#999"}]};var y=0,E=this,n=0,I=0,H=!1;this.setValue=
function(a){n=b.animation?y:a;var d=(b.maxValue-b.minValue)/100;I=a>b.maxValue?b.maxValue+d:a<b.minValue?b.minValue-d:a;y=a;b.animation?k():this.draw();return this};this.setRawValue=function(a){n=y=a;this.draw();return this};this.clear=function(){y=n=I=this.config.minValue;this.draw();return this};this.getValue=function(){return y};this.onready=function(){};l(this.config,b);this.config.minValue=parseFloat(this.config.minValue);this.config.maxValue=parseFloat(this.config.maxValue);b=this.config;n=
y=b.minValue;if(!b.renderTo)throw Error("Canvas element was not specified when creating the Gauge object!");var z=b.renderTo.tagName?b.renderTo:document.getElementById(b.renderTo),a=z.getContext("2d"),A,C,D,t,u,f,B;q();this.updateConfig=function(a){l(this.config,a);q();this.draw();return this};var M={linear:function(a){return a},quad:function(a){return Math.pow(a,2)},quint:function(a){return Math.pow(a,5)},cycle:function(a){return 1-Math.sin(Math.acos(a))},bounce:function(a){a:{a=1-a;for(var b=0,
c=1;;b+=c,c/=2)if(a>=(7-4*b)/11){a=-Math.pow((11-6*b-11*a)/4,2)+Math.pow(c,2);break a}a=void 0}return 1-a},elastic:function(a){a=1-a;return 1-Math.pow(2,10*(a-1))*Math.cos(30*Math.PI/3*a)}},G=null;a.lineCap="round";this.draw=function(){if(!A.i8d){B.clearRect(-t,-u,C,D);B.save();var g={ctx:a};a=B;p();N();J();d();s();b.title&&(a.save(),a.font=24*(f/200)+"px Arial",a.fillStyle=b.colors.title,a.textAlign="center",a.fillText(b.title,0,-f/4.25),a.restore());b.units&&(a.save(),a.font=22*(f/200)+"px Arial",
a.fillStyle=b.colors.units,a.textAlign="center",a.fillText(b.units,0,f/3.25),a.restore());A.i8d=!0;a=g.ctx;delete g.ctx}a.clearRect(-t,-u,C,D);a.save();a.drawImage(A,-t,-u,C,D);if(Gauge.initialized)L(),K(),H||(E.onready&&E.onready(),H=!0);else var e=setInterval(function(){Gauge.initialized&&(clearInterval(e),L(),K(),H||(E.onready&&E.onready(),H=!0))},10);return this}};Gauge.initialized=!1;
(function(){var b=document,l=b.getElementsByTagName("head")[0],q=-1!=navigator.userAgent.toLocaleLowerCase().indexOf("msie"),v="@font-face {font-family: 'Led';src: url('fonts/digital-7-mono."+(q?"eot":"ttf")+"');}",k=b.createElement("style");k.type="text/css";if(q)l.appendChild(k),l=k.styleSheet,l.cssText=v;else{try{k.appendChild(b.createTextNode(v))}catch(e){k.cssText=v}l.appendChild(k);l=k.styleSheet?k.styleSheet:k.sheet||b.styleSheets[b.styleSheets.length-1]}var g=setInterval(function(){if(b.body){clearInterval(g);
var e=b.createElement("div");e.style.fontFamily="Led";e.style.position="absolute";e.style.height=e.style.width=0;e.style.overflow="hidden";e.innerHTML=".";b.body.appendChild(e);setTimeout(function(){Gauge.initialized=!0;e.parentNode.removeChild(e)},250)}},1)})();Gauge.Collection=[];
Gauge.Collection.get=function(b){if("string"==typeof b)for(var l=0,q=this.length;l<q;l++){if((this[l].config.renderTo.tagName?this[l].config.renderTo:document.getElementById(this[l].config.renderTo)).getAttribute("id")==b)return this[l]}else return"number"==typeof b?this[b]:null};function domReady(b){window.addEventListener?window.addEventListener("DOMContentLoaded",b,!1):window.attachEvent("onload",b)}
domReady(function(){function b(b){for(var e=b[0],d=1,g=b.length;d<g;d++)e+=b[d].substr(0,1).toUpperCase()+b[d].substr(1,b[d].length-1);return e}for(var l=document.getElementsByTagName("canvas"),q=0,v=l.length;q<v;q++)if("canv-gauge"==l[q].getAttribute("data-type")){var k=l[q],e={},g,p=parseInt(k.getAttribute("width"),10),w=parseInt(k.getAttribute("height"),10);e.renderTo=k;p&&(e.width=p);w&&(e.height=w);p=0;for(w=k.attributes.length;p<w;p++)if(g=k.attributes.item(p).nodeName,"data-type"!=g&&"data-"==
g.substr(0,5)){var d=g.substr(5,g.length-5).toLowerCase().split("-");if(g=k.getAttribute(g))switch(d[0]){case "colors":d[1]&&(e.colors||(e.colors={}),"needle"==d[1]?(d=g.split(/\s+/),e.colors.needle=d[0]&&d[1]?{start:d[0],end:d[1]}:g):(d.shift(),e.colors[b(d)]=g));break;case "highlights":e.highlights||(e.highlights=[]);g=g.match(/(?:(?:-?\d*\.)?(-?\d+){1,2} ){2}(?:(?:#|0x)?(?:[0-9A-F|a-f]){3,8}|rgba?\(.*?\))/g);for(var d=0,J=g.length;d<J;d++){var s=g[d].replace(/^\s+|\s+$/g,"").split(/\s+/),x={};
s[0]&&""!=s[0]&&(x.from=s[0]);s[1]&&""!=s[1]&&(x.to=s[1]);s[2]&&""!=s[2]&&(x.color=s[2]);e.highlights.push(x)}break;case "animation":d[1]&&(e.animation||(e.animation={}),"fn"==d[1]&&/^\s*function\s*\(/.test(g)&&(g=eval("("+g+")")),e.animation[d[1]]=g);break;default:d=b(d);if("onready"==d)continue;if("majorTicks"==d)g=g.split(/\s+/);else if("strokeTicks"==d||"glow"==d)g="true"==g?!0:!1;else if("valueFormat"==d)if(g=g.split("."),2==g.length)g={"int":parseInt(g[0],10),dec:parseInt(g[1],10)};else continue;
e[d]=g}}e=new Gauge(e);k.getAttribute("data-value")&&e.setRawValue(parseFloat(k.getAttribute("data-value")));k.getAttribute("data-onready")&&(e.onready=function(){eval(this.config.renderTo.getAttribute("data-onready"))});e.draw()}});window.Gauge=Gauge;
<!-- Gauge Code Ends -->
        
        function GetArduinoInputs()
        {
            nocache = "&nocache=" + Math.random() * 1000000;
            var request = new XMLHttpRequest();
            request.onreadystatechange = function()
            {
                if (this.readyState == 4) {
                    if (this.status == 200) {
                        if (this.responseXML != null) {
                            document.getElementById("input3").innerHTML =
                                this.responseXML.getElementsByTagName('analog')[0].childNodes[0].nodeValue;
                            document.getElementById("input4").innerHTML =
                                this.responseXML.getElementsByTagName('analog')[1].childNodes[0].nodeValue;
                            data_val  = this.responseXML.getElementsByTagName('analog')[0].childNodes[0].nodeValue;
                            data_val2 = this.responseXML.getElementsByTagName('analog')[1].childNodes[0].nodeValue;
                        }
                    }
                }
            }
            request.open("GET", "ajax_inputs" + nocache, true);
            request.send(null);
            setTimeout('GetArduinoInputs()', 200);
            
        }
    </script>
    </head>
    <body onload="GetArduinoInputs()">
        <h1>Arduino Ajax Dial</h1>
        <p>Analog (A2): <span id="input3">...</span> Analog (A3): <span id="input4">...</span></p>
        <canvas id="an_gauge_1" data-major-ticks="0 100 200 300 400 500 600 700 800 900 1000 1023" data-type="canv-gauge" data-min-value="0" data-max-value="1023" data-onready="setInterval( function() { Gauge.Collection.get('an_gauge_1').setValue(data_val);}, 200);"></canvas>
        <canvas id="an_gauge_2" data-major-ticks="0 100 200 300 400 500 600 700 800 900 1000 1023" data-type="canv-gauge" data-min-value="0" data-max-value="1023" data-onready="setInterval( function() { Gauge.Collection.get('an_gauge_2').setValue(data_val2);}, 200);"></canvas>
    </body>
</html>

New Variable

At the top of the page in the JavaScript code, a new variable is added to hold the second analog value:

var data_val2 = 0;

New Analog Value Text

In the body of the HTML markup, place is made for displaying the second analog value as text – this is optional.

<p>Analog (A2): <span id="input3">...</span> Analog (A3): <span id="input4">...</span></p>

New Gauge

Below this, the second gauge is created by copying the first gauge and pasting it below the first gauge. Some parameters are changed on the second (pasted) gauge as shown here:

<canvas id="an_gauge_2" data-major-ticks="0 100 200 300 400 500 600 700 800 900 1000 1023" data-type="canv-gauge" data-min-value="0" data-max-value="1023" data-onready="setInterval( function() { Gauge.Collection.get('an_gauge_2').setValue(data_val2);}, 200);"></canvas>

Firstly, the new gauge is given a new name:

an_gauge_2

Next, the new gauge name (an_gauge_2) and new JavaScript variable (data_val2) are now changed in the new gauge code:

... Gauge.Collection.get('an_gauge_2').setValue(data_val2); ...

Getting the Analog Value for the New Gauge

Back in the JavaScript function, the second analog value (A3) is extracted from the XML file sent from the Arduino so that it can be displayed as text and in the gauge.

Analog Value Displayed as Text

document.getElementById("input4").innerHTML =
        this.responseXML.getElementsByTagName('analog')[1].childNodes[0].nodeValue;

Analog Value Put into Variable for Display in Gauge

data_val2 = this.responseXML.getElementsByTagName('analog')[1].childNodes[0].nodeValue;

Amazon.com

Amazon.co.uk


Arduino Sketch Changes

Again, the Arduino sketch is a modified version of the sketch from part 15 of the web server tutorial.

/*--------------------------------------------------------------
  Program:      eth_websrv_SD_Ajax_2_gauge

  Description:  Arduino web server web page displays two Arduino
                analog values on two dial gauges.
                The web page is stored on the SD card.
                Ajax is used to update the analog values on the
                web page.
  
  Hardware:     Arduino Uno and official Arduino Ethernet
                shield. Should work with other Arduinos and
                compatible Ethernet shields.
                2Gb micro SD card formatted FAT16.
                Potentiometers interfaced to A2 & A3 analog
                inputs.
                
  Software:     Developed using Arduino 1.0.5 software
                Should be compatible with Arduino 1.0 +
                SD card contains web page called index.htm
  
  References:   - WebServer example by David A. Mellis and 
                  modified by Tom Igoe
                - SD card examples by David A. Mellis and
                  Tom Igoe
                - Ethernet library documentation:
                  http://arduino.cc/en/Reference/Ethernet
                - SD Card library documentation:
                  http://arduino.cc/en/Reference/SD
                - Gauge from:
                  https://github.com/Mikhus/canv-gauge

  Date:         30 July 2014
 
  Author:       W.A. Smith, http://startingelectronics.org
--------------------------------------------------------------*/

#include <SPI.h>
#include <Ethernet.h>
#include <SD.h>

// size of buffer used to capture HTTP requests
#define REQ_BUF_SZ   50

// MAC address from Ethernet shield sticker under board
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 0, 20); // IP address, may need to change depending on network
EthernetServer server(80);  // create a server at port 80
File webFile;               // the web page file on the SD card
char HTTP_req[REQ_BUF_SZ] = {0}; // buffered HTTP request stored as null terminated string
char req_index = 0;              // index into HTTP_req buffer

void setup()
{
    // disable Ethernet chip
    pinMode(10, OUTPUT);
    digitalWrite(10, HIGH);

    Serial.begin(9600);       // for debugging
    
    // initialize SD card
    Serial.println("Initializing SD card...");
    if (!SD.begin(4)) {
        Serial.println("ERROR - SD card initialization failed!");
        return;    // init failed
    }
    Serial.println("SUCCESS - SD card initialized.");
    // check for index.htm file
    if (!SD.exists("index.htm")) {
        Serial.println("ERROR - Can't find index.htm file!");
        return;  // can't find index file
    }
    Serial.println("SUCCESS - Found index.htm file.");
    
    Ethernet.begin(mac, ip);  // initialize Ethernet device
    server.begin();           // start to listen for clients
}

void loop()
{
    EthernetClient client = server.available();  // try to get client

    if (client) {  // got client?
        boolean currentLineIsBlank = true;
        while (client.connected()) {
            if (client.available()) {   // client data available to read
                char c = client.read(); // read 1 byte (character) from client
                // buffer first part of HTTP request in HTTP_req array (string)
                // leave last element in array as 0 to null terminate string (REQ_BUF_SZ - 1)
                if (req_index < (REQ_BUF_SZ - 1)) {
                    HTTP_req[req_index] = c;          // save HTTP request character
                    req_index++;
                }
                // last line of client request is blank and ends with \n
                // respond to client only after last line received
                if (c == '\n' && currentLineIsBlank) {
                    // send a standard http response header
                    client.println("HTTP/1.1 200 OK");
                    // remainder of header follows below, depending on if
                    // web page or XML page is requested
                    // Ajax request - send XML file
                    if (StrContains(HTTP_req, "ajax_inputs")) {
                        // send rest of HTTP header
                        client.println("Content-Type: text/xml");
                        client.println("Connection: keep-alive");
                        client.println();
                        // send XML file containing input states
                        XML_response(client);
                    }
                    else {  // web page request
                        // send rest of HTTP header
                        client.println("Content-Type: text/html");
                        client.println("Connection: keep-alive");
                        client.println();
                        // send web page
                        webFile = SD.open("index.htm");        // open web page file
                        if (webFile) {
                            while(webFile.available()) {
                                client.write(webFile.read()); // send web page to client
                            }
                            webFile.close();
                        }
                    }
                    // display received HTTP request on serial port
                    Serial.print(HTTP_req);
                    // reset buffer index and all buffer elements to 0
                    req_index = 0;
                    StrClear(HTTP_req, REQ_BUF_SZ);
                    break;
                }
                // every line of text received from the client ends with \r\n
                if (c == '\n') {
                    // last character on line of received text
                    // starting new line with next character read
                    currentLineIsBlank = true;
                } 
                else if (c != '\r') {
                    // a text character was received from client
                    currentLineIsBlank = false;
                }
            } // end if (client.available())
        } // end while (client.connected())
        delay(1);      // give the web browser time to receive the data
        client.stop(); // close the connection
    } // end if (client)
}

// send the XML file containing analog value
void XML_response(EthernetClient cl)
{
    int analog_val;
    
    cl.print("<?xml version = \"1.0\" ?>");
    cl.print("<inputs>");
    // read analog pin A2
    analog_val = analogRead(2);
    cl.print("<analog>");
    cl.print(analog_val);
    cl.print("</analog>");
    analog_val = analogRead(3);
    cl.print("<analog>");
    cl.print(analog_val);
    cl.print("</analog>");
    cl.print("</inputs>");
}

// sets every element of str to 0 (clears array)
void StrClear(char *str, char length)
{
    for (int i = 0; i < length; i++) {
        str[i] = 0;
    }
}

// searches for the string sfind in the string str
// returns 1 if string found
// returns 0 if string not found
char StrContains(char *str, char *sfind)
{
    char found = 0;
    char index = 0;
    char len;

    len = strlen(str);
    
    if (strlen(sfind) > len) {
        return 0;
    }
    while (index < len) {
        if (str[index] == sfind[found]) {
            found++;
            if (strlen(sfind) == found) {
                return 1;
            }
        }
        else {
            found = 0;
        }
        index++;
    }
    return 0;
}

The only change needed in this sketch is to send the second analog value (A3) in the XML file. This is done by adding the second analog value in the XML_response() function.

analog_val = analogRead(3);
cl.print("<analog>");
cl.print(analog_val);
cl.print("</analog>");

This second analog value will then be displayed as text on the already modified web page and in the second gauge.