#!/usr/bin/env python
import RPi.GPIO as GPIO
import time

SDI   = 11
RCLK  = 12
SRCLK = 13

segCode = [0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71,0x80]

def print_msg():
	print 'Program is running...'
	print 'Please press Ctrl+C to end the program...'

def setup():
	GPIO.setmode(GPIO.BOARD)    #Number GPIOs by its physical location
	GPIO.setup(SDI, GPIO.OUT)
	GPIO.setup(RCLK, GPIO.OUT)
	GPIO.setup(SRCLK, GPIO.OUT)
	GPIO.output(SDI, GPIO.LOW)
	GPIO.output(RCLK, GPIO.LOW)
	GPIO.output(SRCLK, GPIO.LOW)

def hc595_shift(dat):
	for bit in range(0, 8):	
		GPIO.output(SDI, 0x80 & (dat << bit))
		GPIO.output(SRCLK, GPIO.HIGH)
		time.sleep(0.001)
		GPIO.output(SRCLK, GPIO.LOW)
	GPIO.output(RCLK, GPIO.HIGH)
	time.sleep(0.001)
	GPIO.output(RCLK, GPIO.LOW)

def loop():
	while True:
		for i in range(0, len(segCode)):
			hc595_shift(segCode[i])
			time.sleep(0.5)

def destroy():   #When program ending, the function is executed. 
	GPIO.cleanup()

if __name__ == '__main__': #Program starting from here 
	print_msg()
	setup() 
	try:
		loop()  
	except KeyboardInterrupt:  
		destroy()