Bench Hardware ~ Raspberry Pi 3B+

#!/usr/bin/env python

import time
import socket
import Adafruit_SSD1306
import RPi.GPIO as GPIO

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont

from subprocess import call


DEFAULT_LOOP_TIMESTEP = 0.25
DEFAULT_FILTER_LENGTH = 4
SHUTDOWN_DISPLAY_TIME = 2

# Raspberry Pi pin configuration:
RST_PIN = 24 		# Unused - but would reset the OLED interface
I2C_SDA_PIN = 2 	# OLED Comm
I2C_SCL_PIN = 3 	# OLED Comm
SHUT_OFF_PIN = 4 	# Input to command shutdown
ACTIVE_PIN = 17 	# Used to detect OS running 


class RaspberryPiFirmware:
	
	def __init__(self, loop_time_step=DEFAULT_LOOP_TIMESTEP, filter_length=DEFAULT_FILTER_LENGTH):	
		self._loop_time_step = loop_time_step
		self._shutoff_filter = [0]*filter_length
		
		self._current_ip_address = self._get_ip_address()
		
		self.display_setup()
		self.print_ip_address(self._current_ip_address)
		
		GPIO.setmode(GPIO.BCM)
		GPIO.setup(SHUT_OFF_PIN, GPIO.IN)
		GPIO.setup(ACTIVE_PIN, GPIO.OUT)
		
		# Set active as soon as script starts
		GPIO.output(ACTIVE_PIN, 1) 

	def _get_ip_address(self):
		ip_address = socket.gethostbyname(socket.gethostname()) 
		return ip_address
		
	def display_setup(self):
		# 128x32 display with hardware I2C:
		self._disp = Adafruit_SSD1306.SSD1306_128_32(rst=RST_PIN)
		
		try:
			# Initialize library.
			self._disp.begin()
			
			# Clear display.
			self._disp.clear()
			self._disp.display()

			# Create blank image for drawing.
			# Make sure to create image with mode '1' for 1-bit color.
			self._width = self._disp.width
			self._height = self._disp.height
			self._image = Image.new('1', (self._width, self._height))

			self._padding = 2
			self._top = self._padding
			self._bottom = self._height - self._padding

			# Get drawing object to draw on image.
			self._draw = ImageDraw.Draw(self._image)

			# Draw a black filled box to clear the image.
			self._draw.rectangle((0,0,self._width,self._height), outline=0, fill=0)

			# Load default font.
			self._font = ImageFont.load_default()
		except:
			pass

	def print_ip_address(self, address):
		try:
			# Draw a black filled box to clear previous text
			self._draw.rectangle((0,0,self._width,self._height/2), outline=0, fill=0)
			
			# Write IP Address
			self._draw.text((self._padding, self._top), 'IP: {0}'.format(address),  font=self._font, fill=255)
			print self._get_ip_address()

			# Display image.
			self._disp.image(self._image)
			self._disp.display()
		except:
			pass
		
	def shutoff_command(self):
		try:
			# Draw a black filled box to clear previous text
			self._draw.rectangle((0,self._height/2,self._width,self._height), outline=0, fill=0)
			
			# Write Shutdown
			self._draw.text((self._padding, self._height/2 + self._padding), 'Shutting Down',  font=self._font, fill=255)
			
			# Display image.
			self._disp.image(self._image)
			self._disp.display()
			
			time.sleep(SHUTDOWN_DISPLAY_TIME)
			
			# Draw a black filled box to clear screen
			self._draw.rectangle((0,0,self._width,self._height), outline=0, fill=0)
			
			# Display image.
			self._disp.image(self._image)
			self._disp.display()
			
		except:
			pass
			
		# Acknowledge shutting off Pi
		GPIO.output(ACTIVE_PIN, 0)
		
		# Command PI to shutdown
		call("sudo shutdown now", shell=True)
		
	def spin(self):
		try:  
			while True: 
				time.sleep(self._loop_time_step) 
				
				# Read shutoff pin, add to buffer and see if should shut off
				self._shutoff_filter.append(1 if GPIO.input(SHUT_OFF_PIN) else 0)
				self._shutoff_filter.pop(0)
				if (sum(self._shutoff_filter) / len(self._shutoff_filter)) >= 0.75:
					self.shutoff_command()
					break
				
				# Check IP address
				ip_address = self._get_ip_address()
				if ip_address != self._current_ip_address:
					self._current_ip_address = ip_address
					self.print_ip_address(self._current_ip_address)

		except:
			GPIO.cleanup() 


if __name__ == "__main__":
	node = RaspberryPiFirmware()
	
	node.spin()