#
# hello.mag.45.py
#
# receive and display magnetic field 
#    hello.mag.45.py serial_port
#
# Neil Gershenfeld 11/3/13
# (c) Massachusetts Institute of Technology 2013
#
# This work may be reproduced, modified, distributed,
# performed, and displayed for any purpose. Copyright is
# retained and must be preserved. The work is provided
# as is; no warranty is provided, and users accept all 
# liability.
#

from Tkinter import *
import serial

WINDOW = 600 # window size
nsamples = 16.0 # number of samples accumulated

def idle(parent,canvas):
   global filter, eps
   try:
      ser.flush()
      value = int(ser.readline())/nsamples;
      
      x = int(.2*WINDOW + (.9-.2)*WINDOW*value/1024.0)

      canvas.itemconfigure("text",text="%.1f"%value)
      canvas.coords('rect1',.2*WINDOW,.05*WINDOW,x,.2*WINDOW)
      canvas.coords('rect2',x,.05*WINDOW,.9*WINDOW,.2*WINDOW)
      canvas.update()
   except ValueError:
      # We seem to get some bit errors every few hundred lines running at 115200 baud.
      pass

   parent.after_idle(idle,parent,canvas)

#
#  check command line arguments
#
if (len(sys.argv) != 2):
   print "command line: hello.mag.45.py serial_port"
   sys.exit()
port = sys.argv[1]
#
# open serial port
#
ser = serial.Serial(port,115200, timeout=5)
#
# set up GUI
#
root = Tk()
root.title('hello.mag.45.py (q to exit)')
root.bind('q','exit')
canvas = Canvas(root, width=WINDOW, height=.25*WINDOW, background='white')
canvas.create_text(.1*WINDOW,.125*WINDOW,text=".33",font=("Helvetica", 24),tags="text",fill="#0000b0")
canvas.create_rectangle(.2*WINDOW,.05*WINDOW,.3*WINDOW,.2*WINDOW, tags='rect1', fill='#b00000')
canvas.create_rectangle(.3*WINDOW,.05*WINDOW,.9*WINDOW,.2*WINDOW, tags='rect2', fill='#0000b0')
canvas.pack()
#
# start idle loop
#
root.after(100,idle,root,canvas)
root.mainloop()