#
# hello.MT6835.RP2040.py
#
# receive and display angle from a magnetic encoder
#    hello.MT6835.RP2040.py serial_port
#
# Quentin Bolsee 3/15/26
# (c) Massachusetts Institute of Technology 2026
#
# 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.
#

import math
import sys
import tkinter

import serial

window = 600


def limits(x, y, r):
    global window
    xmin = x * window - r * window
    ymin = (1 - y) * window - r * window
    xmax = x * window + r * window
    ymax = (1 - y) * window + r * window
    return xmin, ymin, xmax, ymax


def idle(parent, canvas):
    global ser, radius
    ser.write(b"a")
    txt = ser.read_until()
    a = float(txt.rstrip())

    x = math.cos(a)
    y = math.sin(a)

    mag = math.sqrt(x * x + y * y)
    xn = x / mag
    yn = y / mag

    ox = 0.5
    oy = 0.5

    cx = ox + 0.8 * (xn * 0.5)
    cy = oy + 0.8 * (yn * 0.5)

    canvas.coords("circle", limits(cx, cy, 0.05))
    canvas.coords("line", (ox * window, oy * window, cx * window, (1 - cy) * window))
    canvas.update()
    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, 9600)
#
# set up GUI
#
root = tkinter.Tk()
root.title("Magnet (q to exit)")
root.bind("q", "exit")
canvas = tkinter.Canvas(root, width=window, height=window, background="white")
canvas.create_line((0, 0, 0, 0), fill="black", width=3, tags="line")
canvas.create_oval(limits(0.5, 0.5, 0.2), fill="blue", tags="circle")

canvas.pack()

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

ser.close()