#!/bin/python
#
#
# Written by Courtney Krehbiel
# October 2015
#
#
# Purpose is to run as a background program and monitor GPIO 21 to see if it is grounded.
# If high to low (ground) detected it will perform an orderly shutdown of the Raspberry Pi
#
#
import RPi.GPIO as GPIO
import os
import sys
import time

switchpin = 21		# Using GPIO 21, physical pin 40 since it's close to a ground pin.

GPIO.setmode(GPIO.BCM)	# Using BCM numbers, not physical pin numbers

GPIO.setup(switchpin, GPIO.IN, pull_up_down=GPIO.PUD_UP)	# Set as input, and pulled high by default

GPIO.wait_for_edge(switchpin, GPIO.FALLING, bouncetime=200)	# Program will stop at this line and wait for falling edge, if ever.

# If program ever gets here, we're shutting down.

# Define GPIO to LCD mapping
LCD_RS = 14
LCD_E  = 15
LCD_D4 = 17
LCD_D5 = 18
LCD_D6 = 27
LCD_D7 = 22


# Define some device constants
LCD_WIDTH = 16    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

  
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
GPIO.setup(LCD_E, GPIO.OUT)  # E
GPIO.setup(LCD_RS, GPIO.OUT) # RS
GPIO.setup(LCD_D4, GPIO.OUT) # DB4
GPIO.setup(LCD_D5, GPIO.OUT) # DB5
GPIO.setup(LCD_D6, GPIO.OUT) # DB6
GPIO.setup(LCD_D7, GPIO.OUT) # DB7


def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(E_DELAY)

def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command

  GPIO.output(LCD_RS, mode) # RS

  # High bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

  # Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

def lcd_toggle_enable():
  # Toggle enable
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)

def lcd_string(message,line):
  # Send string to display
  message = message.ljust(LCD_WIDTH," ")
  lcd_byte(line, LCD_CMD)

  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)


def haltsystem(ev=None):
	lcd_string("Halting RPi...  ", LCD_LINE_1)
	lcd_string("Pse wait 30 sec.", LCD_LINE_2)
	os.system("sudo shutdown -h now")		# Send command to shutdown the system
#	print 'System being halted'
	sys.exit(0)

# Initialise display
lcd_init()


GPIO.remove_event_detect(switchpin)

# Send some test
lcd_byte(0x01,LCD_CMD) # 000001 Clear display
lcd_string("REBOOT in 15 sec",LCD_LINE_1)
lcd_string("Push agn to HALT",LCD_LINE_2)

time.sleep(2)						# Debounce the keypress to make sure there are two distinct pushes.

GPIO.add_event_detect(switchpin, GPIO.FALLING)  	# wait for any activity

CountDown = 1500

while CountDown > 0:
	if GPIO.event_detected(switchpin):
		haltsystem()
	time.sleep(0.01)
	CountDown = CountDown - 1

# Button not pressed 2nd time, so will reboot instead 
lcd_string("Rebooting RPi...", LCD_LINE_1)
lcd_string("Pse wait 30 sec.", LCD_LINE_2)
#print 'System being rebooted'

#time.sleep(5)

#lcd_init()		# Clean up display
#GPIO.cleanup()		# Tidy up before exit
os.system("sudo reboot")		# Send command to reboot the system


# To run as a background program which takes very few resources, use the command: sudo python sw-shutdown.py &