add_library('serial')

port = "COM5"

def setup():
    size(512, 512)
    #setup the serial port
    print Serial.list()
    LF = 10
    print "Connecting to ", port
    myPort = Serial(this, port, 115200)
    myPort.bufferUntil(LF)
    
x, y = -1, -1    # current values of X and Y (-1 => not yet set)
px, py = -1, -1  # previous values of X and Y (-1 => not yet set)

def draw():
    global x, y                   # X and Y are not local variables
    if x >= 0 and y >= 0:         # X and Y have been set by serialEvent()
        global px, py             # PX and PY are also not local variables
        if px >= 0 and py >= 0:   # PX and PY have been set from valid X and Y
            line(px, py, x, y)    # draw a line from previous X,Y to current X,Y
        px, py = x, y             # copy valid X,Y to previous X,Y (even if no line was drawn)
     
def serialEvent(evt):
    xy = evt.readString().strip().split()
    if len(xy) == 2:
        global x, y
        x, y = int(xy[0])/2, int(xy[1])/2