Web Server for Thermostat RTC

/*--------------------------------------------------------------
Ajax server sketch that serves web page from SD card and sends serial commands to another Arduino
running a thermostat and recieves variable values to send to web client.
steve.a.mccluskey@gmail.com

  Modified from sketch found at
  http://startingelectronics.com/tutorials/arduino/ethernet-shield-web-server-tutorial/SD-card-AJAX-XML-web-server/
  Original Author:  W.A. Smith, http://startingelectronics.com
  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

Pin layout:
0  : Hardware serial RX.
1  : Hardware serial TX.
2  :
3 ~:
4  : SD CS.
5 ~:
6 ~:
7  :
8  :
9 ~:
10~: Ethernet shield CS.
11~: Ethernet shield MOSI.
12 : Ethernet shield MISO.
13 : Ethernet shield CLK.

Revisions:
1.2: Added code to handle if sensor is unplugged on the web page, 02/18/14.
1.2: Added support for temps down to -40F. 02/20/14.
--------------------------------------------------------------*/

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

#define REQ_BUF_SZ 60 // size of buffer used to capture HTTP requests.

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 1, 179); // IP address, may need to change depending on network.
EthernetServer server(80); // create a server at port 80.
File webFile;
char HTTP_req[REQ_BUF_SZ] = {0}; // buffered HTTP request stored as null terminated string.
char req_index = 0; // index into HTTP_req buffer.

//variables to serve:
uint8_t tempHold = 0;
int8_t tempAvg = 0;
uint8_t hour = 0;
uint8_t eveningHour = 0;
uint8_t morningHour = 0;
uint8_t tempReduction = 0;
uint8_t door = 0;
uint8_t heater = 0;
int8_t temp1 = 0;
int8_t temp2 = 0;
int8_t temp3 = 0;
int8_t tempOut = 0;

unsigned long timeNow = 0, lastUpdate = 0;
String readString;

void setup() {
  pinMode(10, OUTPUT);
  digitalWrite(10, HIGH); // disable Ethernet chip.
  Serial.begin(19200);

  if (!SD.begin(4)) { // initialize SD card.
    return;    // init failed.
  } //end if.

  if (!SD.exists("index.htm")) { // check for index.htm file.
    return;  // can't find index file.
  } //end if.

  Ethernet.begin(mac, ip);
  server.begin();
} //end setup().

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

  if (timeNow - lastUpdate > 10000) { //keeps data fresh when no client connected.
    Serial.println(F("*"));
    lastUpdate = millis();
  } //end if.

  if (client) {  // got client?
    boolean currentLineIsBlank = true;
    while (client.connected()) {
      if (client.available()) {
        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++;
        } //end if.

        // 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(F("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.
            Serial.println(F("*")); //request all values from thermostat.
            client.println(F("Content-Type: text/xml"));
            client.println(F("Connection: keep-alive"));
            client.println();
            sendCommands();
            XML_response(client); //send XML file containing input states.
          } //end if.
          else { // web page request.
            // send rest of HTTP header:
            client.println(F("Content-Type: text/html"));
            client.println(F("Connection: keep-alive"));
            client.println();

            // send web page:
            webFile = SD.open("index.htm");
            if (webFile) {
              while(webFile.available()) {
                client.write(webFile.read()); //send web page to client.
              } //end while.
              webFile.close();
            } //end if.
          } //end else.

          //Serial.print(HTTP_req); // display received HTTP request on serial port.

          // reset buffer index and all buffer elements to 0:
          req_index = 0;
          StrClear(HTTP_req, REQ_BUF_SZ);
          break;
        } //end if.

        // 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;
        }  //end if.
        else if (c != '\r') { // a text character was received from client.
          currentLineIsBlank = false;
        } //end if.
      } // 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).
} //end loop().

// checks if received HTTP request contains certain strings then issues serial commands accordingly.
void sendCommands(void) {
  if (StrContains(HTTP_req, "tempUp")) {
    Serial.println(F("h"));  // increase hold temp.
  } //end if.
  else if (StrContains(HTTP_req, "tempDn")) {
    Serial.println(F("n"));  // decrease hold temp.
  } //end else if
  else if (StrContains(HTTP_req, "nightUp")) {
    Serial.println(F("e"));  // night hour increase.
  } //end else if
  else if (StrContains(HTTP_req, "nightDn")) {
    Serial.println(F("d")); // night hour decrease.
  } //end else if
  else if (StrContains(HTTP_req, "dayUp")) {
    Serial.println(F("m")); // day hour increase.
  } //end else if
  else if (StrContains(HTTP_req, "dayDn")) {
    Serial.println(F("j")); //day hour decrease.
  } //end else if
  else if (StrContains(HTTP_req, "tempRUp")) {
    Serial.println(F("t")); // increase temp reduction.
  } //end else if
  else if (StrContains(HTTP_req, "tempRDn")) {
    Serial.println(F("g")); //decrease temp reduction.
  } //end else if
} //end sendCommands().

// send the XML file with current variable values
void XML_response(EthernetClient cl) {
  cl.print(F("<?xml version = \"1.0\" ?>"));
  cl.print(F("<inputs>"));
  cl.print(F("<tempAvg>"));
  cl.print(tempAvg);
  cl.print(F("</tempAvg>"));
  cl.print(F("<tempHold>"));
  cl.print(tempHold);
  cl.print(F("</tempHold>"));
  cl.print(F("<hour>"));
  cl.print(hour);
  cl.print(F("</hour>"));
  cl.print(F("<eveningHour>"));
  cl.print(eveningHour - 12);
  cl.print(F("</eveningHour>"));
  cl.print(F("<morningHour>"));
  cl.print(morningHour);
  cl.print(F("</morningHour>"));
  cl.print(F("<tempReduction>"));
  cl.print(tempReduction);
  cl.print(F("</tempReduction>"));
  cl.print(F("<doorState>"));
  cl.print(door);
  cl.print(F("</doorState>"));
  cl.print(F("<heaterState>"));
  cl.print(heater);
  cl.print(F("</heaterState>"));
  cl.print(F("<sensors>"));
  if (temp1 >= -40) {
    cl.print(temp1);
  } //end if.
  else {
    cl.print(F("--"));
  } //end else.
  cl.print(F("</sensors>"));
  cl.print(F("<sensors>"));
  if (temp2 >= -40) {
    cl.print(temp2);
  } //end if.
  else {
    cl.print(F("--"));
  } //end else.
  cl.print(F("</sensors>"));
  cl.print(F("<sensors>"));
  if (temp3 >= -40) {
    cl.print(temp3);
  } //end if.
  else {
    cl.print(F("--"));
  } //end else.
  cl.print(F("</sensors>"));
  cl.print(F("<sensors>"));
  if (tempOut >= -40) {
    cl.print(tempOut);
  } //end if.
  else {
    cl.print(F("--"));
  } //end else.
  cl.print(F("</sensors>"));
  cl.print(F("</inputs>"));
} //end XML_response().

// sets every element of str to 0 (clears array)
void StrClear(char *str, char length) {
  for (uint8_t i = 0; i < length; i++) {
    str[i] = 0;
  } //end for.
} //end StrClear().

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

void serialEvent() { //recieves all values from thermostat and saves to global values.
  while (Serial.available()) {
    char c = Serial.read();
    readString += c;

    if (c == '*') { //end of packet.
      uint8_t holdEnd = readString.indexOf('h');
      uint8_t avgEnd = readString.indexOf('a');
      uint8_t hourEnd = readString.indexOf('j');
      uint8_t eveningEnd = readString.indexOf('e');
      uint8_t morningEnd = readString.indexOf('m');
      uint8_t reductionEnd = readString.indexOf('t');
      uint8_t doorEnd = readString.indexOf('d');
      uint8_t heaterEnd = readString.indexOf('f');
      uint8_t temp1End = readString.indexOf('x');
      uint8_t temp2End = readString.indexOf('y');
      uint8_t temp3End = readString.indexOf('z');
      uint8_t tempOutEnd = readString.indexOf('w');

      String hold = readString.substring(0, holdEnd);
      tempHold = hold.toInt();
      String avg = readString.substring(holdEnd + 1, avgEnd);
      tempAvg = avg.toInt();
      String hour1 = readString.substring(avgEnd + 1, hourEnd);
      hour = hour1.toInt();
      String evening = readString.substring(hourEnd + 1, eveningEnd);
      eveningHour = evening.toInt();
      String morning = readString.substring(eveningEnd + 1, morningEnd);
      morningHour = morning.toInt();
      String reduction = readString.substring(morningEnd + 1, reductionEnd);
      tempReduction = reduction.toInt();
      String doorCheck = readString.substring(reductionEnd + 1, doorEnd);
      door = doorCheck.toInt();
      String heaterCheck = readString.substring(doorEnd + 1, heaterEnd);
      heater = heaterCheck.toInt();
      String temp1Check = readString.substring(heaterEnd + 1, temp1End);
      if (temp1Check == "--") {
        temp1 = -41;
      } //end if.
      else {
        temp1 = temp1Check.toInt();
      } //end else.
      String temp2Check = readString.substring(temp1End + 1, temp2End);
      if (temp2Check == "--") {
        temp2 = -41;
      } //end if.
      else {
        temp2 = temp2Check.toInt();
      } //end else.
      String temp3Check = readString.substring(temp2End + 1, temp3End);
      if (temp3Check == "--") {
        temp3 = -41;
      } //end if.
      else {
        temp3 = temp3Check.toInt();
      } //end else.
      String tempOutCheck = readString.substring(temp3End + 1, tempOutEnd);
      if (tempOutCheck == "--") {
        tempOut = -41;
      } //end if.
      else {
        tempOut = tempOutCheck.toInt();
      } //end else.

      readString = "";
    } //end if.
  } //end while.
} //end serialEvent().