TeensyEtchaSketch(work_in_progress)

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

File dataFile;

byte mac[] = {
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};
IPAddress ip(10, 1, 0, 177);
EthernetServer server(80);
//Function defs
void startPage(EthernetClient client);
void endPage(EthernetClient client);
void svgHeader(EthernetClient client);
void svgFooter(EthernetClient client);
void polyLineBegin(EthernetClient client);
void polyLineEnd(EthernetClient client);

int Reset = 4;     //programticaly reset the arduino
int potX = A0;
int potY = A1;

int sensorValX = 0;
int sensorValY = 0;

int oldX = 0;
int oldY = 0;

void setup() {

  delay(5000);  //you want this delay. reason: tl;dr
  Serial.begin(9600);
  Ethernet.begin(mac, ip);

if (Ethernet.linkStatus() == LinkOFF) {
    Serial.println("Ethernet cable is not connected.");
  }

  // start the server
  server.begin();
  delay(100);
  Serial.print("server is at ");
  Serial.println(Ethernet.localIP());

  Serial.print("Initializing SD card...");

  if (!SD.begin(BUILTIN_SDCARD)) {
    Serial.println("SD Card init failed!");
    while (1);
  }
/****SD CARD and Ethernet intialized*****/
//if data file (on SD Card) Doesn't exist, create it.
//if data file (on SD Card) does exist errase it and create a new one


  if (SD.exists("datalog.txt")) {
    Serial.println("datalog.txt exists: \n Removing it.");
    SD.remove("datalog.txt");
  } else {
    Serial.println("datalog.txt doesn't exist.");
  }

  // open a new file and immediately close it:
  Serial.println("Creating datalog.txt...");
  dataFile = SD.open("datalog.txt", FILE_WRITE);
  dataFile.close();

  // Check to see if the file exists:
  if (SD.exists("datalog.txt")) {
    Serial.println("datalog.txt exists.");
  } else {
    Serial.println("datalog.txt wasn't created.");
}
} //end setup

void loop() {
  int sensorValX = analogRead(8);
  int sensorValY = analogRead(9);
  String dataString = "";
  int threshold =3;
  int xVariance = abs(sensorValX-oldX);
  int yVariance = abs(sensorValY-oldY);

if (xVariance >=threshold && yVariance >= threshold ||xVariance >=threshold || yVariance >=threshold){
//if sensor data is greater than threshold, write data to the sd card, then close the file
SD.open("datalog.txt", FILE_WRITE);
dataString += String(sensorValX);
dataString += ",";
dataString += String(sensorValY);
   dataFile = SD.open("datalog.txt", FILE_WRITE);

  // if the file is available, write to it:
  if (dataFile) {
    dataFile.println(dataString);
    dataFile.close();
//clear dataString
dataString="";
  } else {
    // if the file isn't open, pop up an error:
    Serial.println("error opening datalog.txt");
  }
dataFile.close();

} //end threshold

 // listen for incoming clients
  EthernetClient client = server.available();
   if (client) {
    boolean currentLineIsBlank = true;
    while (client.connected()) {
       if (client.available()) {
          char c = client.read();
       // Serial.write(c);   //tells about the client connection
        if (c == '\n' && currentLineIsBlank) {
            startPage(client);
 svgHeader(client);
   polyLineBegin(client);
   polyLineEnd(client);
 svgFooter(client);

          endPage(client);
          break;
        }
        if (c == '\n') {
          // you're starting a new line
          currentLineIsBlank = true;
        } else if (c != '\r') {
          // you've gotten a character on the current line
          currentLineIsBlank = false;
        }
      }//end avail
    } //end conect
    // give the web browser time to receive the data
    delay(1);
    // close the connection:
    client.stop();
  } //end client
}  //end loop

void startPage(EthernetClient client){
     // send a standard http response header
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("Connection: close");  // the connection will be closed after completion of the response
          client.println("Refresh: 5");  // refresh the page automatically every 5 sec
          client.println();
          client.println("<!DOCTYPE HTML>");
          client.println("<html>");
  }

 void endPage(EthernetClient client){
  client.println("</body>");
  client.println("</html>");
  }


void polyLineBegin(EthernetClient client){
  client.print("<polyline points=\""); //x,y points go here
  //read data from SD card
    File dataFile = SD.open("datalog.txt");

  // if the file is available, read it:
  if (dataFile) {
    while (dataFile.available()) {
      Serial.write(dataFile.read());
      client.write(dataFile.read());
    }
    dataFile.close();
  }
}

void polyLineEnd(EthernetClient client){
   client.println ("0, 0\" stroke=\"red\" fill=\"transparent\" stroke-width=\"5\"/>");  //a dirty hack to avoid dealing with 1 last trailing comma.
  }

void svgHeader(EthernetClient client){
client.println("<svg width=\"1023\" height=\"1023\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\">");
  };

void svgFooter(EthernetClient client){
client.println ("</svg>");
  }