drawing program problem with processing

I ve got a tablet hook up to arduino which send 3 variables to processing : penStatus, x, y in ascii string
In processing i ve set up a drawing sketch which splits the string then interprets x and y to do some drawing.
But the lines are not continuous and kind of "laggy". it seems that it can't keep up with the speed of the stylus; it only draws small xtoy points and jumps to another one with no connection lines between them, i ve joined the processing sketch and a picture of the results.
thanks for any help.

import processing.serial.*;

 Serial myPort;                       // The serial port
 
 
 int x = 0;
 int y = 0;

 int oldx = 0;
 int oldy = 0;
 int penStatus = 0;


  

 void setup()
 {
   size(3200,2400);
   frameRate(25);
   background(0);
   smooth();
   stroke (204, 102, 0);
   strokeWeight(5);
   strokeJoin(MITER);
   
   myPort = new Serial(this, "COM5", 19200); 
   myPort.bufferUntil('\n');
  
 }

void serialEvent(Serial myPort) {
     
     oldx = x;
     oldy = y;
  
  // read the serial buffer:
   String myString = myPort.readStringUntil('\n');
   // if you got any bytes other than the linefeed:
     myString = trim(myString);
  
     // split the string at the commas
     // and convert the sections into integers:
     int sensors[] = int(split(myString, ','));
 
    // print out the values you got:
     for (int sensorNum = 0; sensorNum < sensors.length; sensorNum++) {
      print("Sensor " + sensorNum + ": " + sensors[sensorNum] + "\t");
      println();
     
     penStatus = sensors[0];
     x = sensors[1];
     y = sensors[2];
     
     
     print(oldx);
     print(oldy);
     print(x);
     println(y);
     
     
    }
 
}


 void draw() {
   
   line (oldx, oldy, x, y);
   
   

  
 }

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