from Tkinter import *			# TKinter - needs to be installed first
import serial
import time

DEVICE = '/dev/ttyACM0'
BAUD = 9600
ser = serial.Serial(DEVICE, BAUD)

root = Tk()

def aUp() :
    ser.write('a')
    return

def aDown() :
    ser.write('A')
    return

Button(text='A up', command=aUp).pack()
Button(text='A down', command=aDown).pack()

root.mainloop()