#
# hello.temp.45.py
#
# receive and display temperature
# hello.temp.45.py serial_port
#
# Neil Gershenfeld
# CBA MIT 3/27/12
#
# (c) Massachusetts Institute of Technology 2012
# Permission granted for experimental and personal use;
# license for commercial sale available from MIT
#

from tkinter import *
from numpy import log
from serial import Serial

WINDOW = 400 # window size
eps = 0.5 # filter time constant
filter = 0.0 # filtered value

def fahrenheit(T):
    return T*9/5 + 32

def idle(parent,canvas, units="celsius"):
   global filter, eps
   #
   # idle routine
   #
   byte2 = 0
   byte3 = 0
   byte4 = 0
   ser.flush()
   while 1:
      #
      # find framing 
      #
      byte1 = byte2
      byte2 = byte3
      byte3 = byte4
      byte4 = ord(ser.read())
      if ((byte1 == 1) & (byte2 == 2) & (byte3 == 3) & (byte4 == 4)):
         break
   low = ord(ser.read())
   high = ord(ser.read())
   value = 256*high + low
   if (value > 511):
      value -= 1024
   V = 2.5 - value*5.0/(20.0*512.0)
   R = 10000.0/(5.0/V-1.0)
   # NHQ103B375R5
   # R25 10000 (O)
   # B (25/85) 3750 (K)
   # R(T(C)) = R(25)*exp(B*(1/(T(C)+273.15)-(1/(25+273.15))))
   B = 3750.0
   R25 =  10000.0
   T = fahrenheit(1.0/(log(R/R25)/B+(1/(25.0+273.15))) - 273.15)
   # filter = (1-eps)*filter + eps*T
   # print(filter)
   x=WINDOW*(1-T/100)
   # x = int(.2*WINDOW + (.9-.2)*WINDOW*(filter-20.0)/10.0)
   canvas.itemconfigure("text",text="%.2f"%round(T,2))
   canvas.coords('rect1',.05*WINDOW,.6*WINDOW + x,.2*WINDOW,WINDOW)
   # canvas.coords('rect2',.05*WINDOW,.1*WINDOW,.2*WINDOW, .1*WINDOW + x)
   canvas.update()
   parent.after_idle(idle,parent,canvas)




#  check command line arguments
#
if (len(sys.argv) != 2):
   print("command line: hello.temp.45.py serial_port")
   sys.exit()
port = sys.argv[1]
#
# open serial port
#
ser = Serial(port,9600)
ser.setDTR()
#
# start plotting
#
root = Tk()
root.title('How Hot?')
root.bind('q','exit')
canvas = Canvas(root, width=.25*WINDOW, height=1.433*WINDOW, background='black')
canvas.create_rectangle(.05*WINDOW,.1*WINDOW,.2*WINDOW,WINDOW, tags='rect2', fill='#dffeff')
canvas.create_rectangle(.05*WINDOW,.6*WINDOW,.2*WINDOW,WINDOW, tags='rect1', fill='#ffcbcb')
canvas.create_oval(.01*WINDOW,.9*WINDOW,.24*WINDOW,1.13*WINDOW, tags='oval1', fill='#ffcbcb', outline="")
canvas.create_text(.15*WINDOW,1.25*WINDOW,text=".33",font=("Helvetica", 24),tags="text",fill="#ffffff")
canvas.pack()
b = Button(root, text="Exit", command=root.destroy)
b.pack()
root.after(100,idle,root,canvas)
root.mainloop()