import RPi.GPIO as gpio
import time
import sys
import Tkinter as tk
from sensor import distance



def init():
    gpio.setmode(gpio.BOARD)
    gpio.setup(7, gpio.OUT)
    gpio.setup(11, gpio.OUT)
    gpio.setup(13, gpio.OUT)
    gpio.setup(15, gpio.OUT)

def forward(tf):
    gpio.output(7, False)
    gpio.output(11, True)
    gpio.output(13, True)
    gpio.output(15, False)
    time.sleep(tf)
    gpio.cleanup()

def reverse(tf):
    gpio.output(7, True)
    gpio.output(11, False)
    gpio.output(13, False)
    gpio.output(15, True)
    time.sleep(tf)
    gpio.cleanup()

def turn_left(tf):
    gpio.output(7, True)
    gpio.output(11, True)
    gpio.output(13, True)
    gpio.output(15, False)
    time.sleep(tf)
    gpio.cleanup()

def turn_right(tf):
    gpio.output(7, False)
    gpio.output(11, True)
    gpio.output(13, False)
    gpio.output(15, False)
    time.sleep(tf)
    gpio.cleanup()

def pivot_left(tf):
    gpio.output(7, True)
    gpio.output(11, False)
    gpio.output(13, True)
    gpio.output(15, False)
    time.sleep(tf)
    gpio.cleanup()

def pivot_right(tf):
    gpio.output(7, False)
    gpio.output(11, True)
    gpio.output(13, False)
    gpio.output(15, True)
    time.sleep(tf)
    gpio.cleanup()



def key_input(event):
    init()
    print 'Key:', event.char
    key_press = event.char
    sleep_time = 0.030

    if key_press.lower() == 'w':
        forward(sleep_time)
    elif key_press.lower() == 's':
        reverse(sleep_time)
    elif key_press.lower() == 'a':
        turn_left(sleep_time)
    elif key_press.lower() == 'd':
        turn_right(sleep_time)
    elif key_press.lower() == 'q':
        pivot_left(sleep_time)
    elif key_press.lower() == 'e':
        pivot_right(sleep_time)
    else:
        pass

    curDis = distance('cm')
    print('curdis is',curDis)

    if curDis < 20:
        init()
        reverse(2)




command = tk.Tk()
command.bind('<KeyPress>', key_input)
command.mainloop()


		

Now that we understand the distance sensor, and we've got this neat little sensor module written up, let's incorporate it into our car

First, let's use it as a sort of auto-pilot. Some cars today already will apply your brakes for you if they sense you are getting too close to another car, this is sort of like that.

All we really need to do is do some distance checks within our tkinter key-logging loop. If the distance check yields a distance less than an acceptable distance, then stop. Easy enough!

Not only will we stop here, but we're also going to apply an instantaneous reversal.