Instalación y programación.

Con esta aplicación podemos conocer el valor de 4 entradas analógicas, 3 digitales y activar 4 salidas digitales; con Arduino UNO y la placa de conexión a Ethernet W5100, desde cualquier equipo conectado a Internet.

La parte primera del programa hay que cargarla en el Arduino UNO y la segunda parte en la tarjeta microSD que lleva el módulo W5100.

La página Web será la siguiente:

#include <SPI.h>
#include <Ethernet.h>
#include <SD.h>
// size of buffer used to capture HTTP requests
#define REQ_BUF_SZ 60

// MAC address from Ethernet shield sticker under board
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 1, 15); // 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
boolean LED_state[4] = {0}; // stores the states of the LEDs

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.");
 // switches on pins 2, 3 and 5
 pinMode(2, INPUT);
 pinMode(3, INPUT);
 pinMode(5, INPUT);
 // LEDs
 pinMode(6, OUTPUT);
 pinMode(7, OUTPUT);
 pinMode(8, OUTPUT);
 pinMode(9, OUTPUT);
 
 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
 // limit the size of the stored received HTTP request
 // 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();
 SetLEDs();
 // 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)
}

// checks if received HTTP request is switching on/off LEDs
// also saves the state of the LEDs
void SetLEDs(void)
{
 // LED 1 (pin 6)
 if (StrContains(HTTP_req, "LED1=1")) {
 LED_state[0] = 1; // save LED state
 digitalWrite(6, HIGH);
 }
 else if (StrContains(HTTP_req, "LED1=0")) {
 LED_state[0] = 0; // save LED state
 digitalWrite(6, LOW);
 }
 // LED 2 (pin 7)
 if (StrContains(HTTP_req, "LED2=1")) {
 LED_state[1] = 1; // save LED state
 digitalWrite(7, HIGH);
 }
 else if (StrContains(HTTP_req, "LED2=0")) {
 LED_state[1] = 0; // save LED state
 digitalWrite(7, LOW);
 }
 // LED 3 (pin 8)
 if (StrContains(HTTP_req, "LED3=1")) {
 LED_state[2] = 1; // save LED state
 digitalWrite(8, HIGH);
 }
 else if (StrContains(HTTP_req, "LED3=0")) {
 LED_state[2] = 0; // save LED state
 digitalWrite(8, LOW);
 }
 // LED 4 (pin 9)
 if (StrContains(HTTP_req, "LED4=1")) {
 LED_state[3] = 1; // save LED state
 digitalWrite(9, HIGH);
 }
 else if (StrContains(HTTP_req, "LED4=0")) {
 LED_state[3] = 0; // save LED state
 digitalWrite(9, LOW);
 }
}

// send the XML file with analog values, switch status
// and LED status
void XML_response(EthernetClient cl)
{
 int analog_val; // stores value read from analog inputs
 int count; // used by 'for' loops
 int sw_arr[] = {2, 3, 5}; // pins interfaced to switches
 
 cl.print("<?xml version = \"1.0\" ?>");
 cl.print("<inputs>");
 // read analog inputs
 for (count = 2; count <= 5; count++) { // A2 to A5
 if (count == 2) //Añadimos este código para escalar las señales analógicas
 {analog_val = analogRead(count);}
 if (count == 3)
 {analog_val = analogRead(count);}
 if (count == 4)
 {analog_val = analogRead(count)*5*100/1024;} //Escalamos la entrada para un sensor de temperatura LM35
 if (count == 5)
 {analog_val = analogRead(count)*5*100/1024;} //Escalamos la entrada para un sensor de temperatura LM35
 
 cl.print("<analog>");
 cl.print(analog_val);
 cl.println("</analog>");
 }
 // read switches
 for (count = 0; count < 3; count++) {
 cl.print("<switch>");
 if (digitalRead(sw_arr[count])) {
 cl.print("ON");
 }
 else {
 cl.print("OFF");
 }
 cl.println("</switch>");
 }
 // checkbox LED states
 // LED1
 cl.print("<LED>");
 if (LED_state[0]) {
 cl.print("checked");
 }
 else {
 cl.print("unchecked");
 }
 cl.println("</LED>");
 // LED2
 cl.print("<LED>");
 if (LED_state[1]) {
 cl.print("checked");
 }
 else {
 cl.print("unchecked");
 }
 cl.println("</LED>");
 // button LED states
 // LED3
 cl.print("<LED>");
 if (LED_state[2]) {
 cl.print("on");
 }
 else {
 cl.print("off");
 }
 cl.println("</LED>");
 // LED4
 cl.print("<LED>");
 if (LED_state[3]) {
 cl.print("on");
 }
 else {
 cl.print("off");
 }
 cl.println("</LED>");
 
 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;
}

El programa que hay que introducir en la microSD de la placa W5100 que nos comunica por Ethernet, debe tener el nombre «index.htm». Podremos activar las salidas y recibir la información de las entradas digitales y analógicas desde  cualquier lugar del mundo.

<!DOCTYPE html>
<html>
<head>
 <title>Arduino</title>
 <script>
strLED1 = "";
strLED2 = "";
strLED3 = "";
strLED4 = "";
var LED3_state = 0;
var LED4_state = 0;
function GetArduinoIO()
{
nocache = "&nocache=" + Math.random() * 1000000;
var request = new XMLHttpRequest();
request.onreadystatechange = function()
{
if (this.readyState == 4) {
if (this.status == 200) {
if (this.responseXML != null) {
// XML file received - contains analog values, switch values and LED states
var count;
// get analog inputs
var num_an = this.responseXML.getElementsByTagName('analog').length;
for (count = 0; count < num_an; count++) {
document.getElementsByClassName("analog")[count].innerHTML =
this.responseXML.getElementsByTagName('analog')[count].childNodes[0].nodeValue;
}
// get switch inputs
var num_an = this.responseXML.getElementsByTagName('switch').length;
for (count = 0; count < num_an; count++) {
document.getElementsByClassName("switches")[count].innerHTML =
this.responseXML.getElementsByTagName('switch')[count].childNodes[0].nodeValue;
}
// LED 1
if (this.responseXML.getElementsByTagName('LED')[0].childNodes[0].nodeValue === "checked") {
document.LED_form.LED1.checked = true;
}
else {
document.LED_form.LED1.checked = false;
}
// LED 2
if (this.responseXML.getElementsByTagName('LED')[1].childNodes[0].nodeValue === "checked") {
document.LED_form.LED2.checked = true;
}
else {
document.LED_form.LED2.checked = false;
}
// LED 3
if (this.responseXML.getElementsByTagName('LED')[2].childNodes[0].nodeValue === "on") {
document.getElementById("LED3").innerHTML = "SALIDA 8 ON ";
LED3_state = 1;
}
else {
document.getElementById("LED3").innerHTML = "SALIDA 8 OFF ";
LED3_state = 0;
}
// LED 4
if (this.responseXML.getElementsByTagName('LED')[3].childNodes[0].nodeValue === "on") {
document.getElementById("LED4").innerHTML = "SALIDA 9 ON ";
LED4_state = 1;
}
else {
document.getElementById("LED4").innerHTML = "SALIDA 9 OFF ";
LED4_state = 0;
}
}
}
}
}
// send HTTP GET request with LEDs to switch on/off if any
request.open("GET", "ajax_inputs" + strLED1 + strLED2 + strLED3 + strLED4 + nocache, true);
request.send(null);
setTimeout('GetArduinoIO()', 1000);
strLED1 = "";
strLED2 = "";
strLED3 = "";
strLED4 = "";
}
// service LEDs when checkbox checked/unchecked
function GetCheck()
{
if (LED_form.LED1.checked) {
strLED1 = "&LED1=1";
}
else {
strLED1 = "&LED1=0";
}
if (LED_form.LED2.checked) {
strLED2 = "&LED2=1";
}
else {
strLED2 = "&LED2=0";
}
}
function GetButton1()
{
if (LED3_state === 1) {
LED3_state = 0;
strLED3 = "&LED3=0";
}
else {
LED3_state = 1;
strLED3 = "&LED3=1";
}
}
function GetButton2()
{
if (LED4_state === 1) {
LED4_state = 0;
strLED4 = "&LED4=0";
}
else {
LED4_state = 1;
strLED4 = "&LED4=1";
}
}
 </script>
 <style>
.IO_box {
float: left;
margin: 0 20px 20px 0;
border: 1px solid blue;
padding: 0 5px 0 5px;
width: 120px;
}
h1 {
font-size: 120%;
color: blue;
margin: 0 0 10px 0;
}
h2 {
font-size: 85%;
color: #5734E6;
margin: 5px 0 5px 0;
}
p, form, button {
font-size: 80%;
color: #252525;
}
.small_text {
font-size: 70%;
color: #737373;
}
 </style>
</head>
<body onload="GetArduinoIO()">
<h1>Arduino</h1>
<div class="IO_box">
<h2>Entradas anal&oacute;gicas</h2>
<p>A2: <span class="analog">...</span></p>
<p>A3: <span class="analog">...</span></p>
<p>Tª interior: <span class="analog">...</span>ºC</p>
<p>Tª exterior: <span class="analog">...</span>ºC</p>
</div>
<div class="IO_box">
<h2>Entradas</h2>
<p>Entrada 2: <span class="switches">...</span></p>
<p>Entrada 3: <span class="switches">...</span></p>
<p>Entrada 5: <span class="switches">...</span></p>
</div>
<div class="IO_box">
<h2>Salidas</h2>
<form id="check_LEDs" name="LED_form"> <input
 name="LED1" value="0" onclick="GetCheck()"
 type="checkbox">Salida 6<br>
 <br>
 <input name="LED2" value="0" onclick="GetCheck()"
 type="checkbox">Salida 7<br>
 <br>
</form>
</div>
<div class="IO_box">
<h2>Salidas</h2>
<button type="button" id="LED3" onclick="GetButton1()">SALIDA
8 OFF </button><br>
<br>
<button type="button" id="LED4" onclick="GetButton2()">SALIDA
9 OFF </button><br>
<br>
</div>
</body>
</html>