from tkinter import *
import serial

WINDOW = 600 # windows size

ser = serial.Serial('/dev/tty.usbserial-AC01N5D9', 1200)

# runs on a loop and updates the canvas to reflect the new readings
def idle(parent, canvas):
    line = str(ser.readline()) # b'522\r\n'
    val = 0
    try:
        val = int(line[2:-5])
    except:
        pass

    x1 = int(.2*WINDOW + (.9-.2)*WINDOW*val/1023.0)
    canvas.itemconfigure("text1",text="%d"%val)
    canvas.coords('rect11',.2*WINDOW,.05*WINDOW,x1,.2*WINDOW)
    canvas.coords('rect12',x1,.05*WINDOW,.9*WINDOW,.2*WINDOW)
    canvas.update()
    parent.after_idle(idle, parent, canvas)

# initializes the Tkinter window
root = Tk()
root.title('Hall Effect Sensor (q to exit)')
root.bind('q','exit')
canvas = Canvas(root, width=WINDOW, height=.75*WINDOW, background='white')

# builds the UI
canvas.create_text(.1*WINDOW,.125*WINDOW,text="1",font=("Helvetica", 24),tags="text1",fill="#0000b0")
canvas.create_rectangle(.2*WINDOW,.05*WINDOW,.3*WINDOW,.2*WINDOW, tags='rect11', fill='#b00000')
canvas.create_rectangle(.3*WINDOW,.05*WINDOW,.9*WINDOW,.2*WINDOW, tags='rect12', fill='#0000b0')
canvas.pack()

root.after(100, idle, root, canvas)
root.mainloop()