rotary_class.py

#!/usr/bin/env python
#
# Raspberry Pi Rotary Encoder Class
# $Id: rotary_class.py,v 1.2 2014/01/31 13:34:48 bob Exp $
#
# Author : Bob Rathbone
# Site   : http://www.bobrathbone.com
#
# This class uses standard rotary encoder with push switch
# 
#

import RPi.GPIO as GPIO

class RotaryEncoder:

	CLOCKWISE=1
	ANTICLOCKWISE=2
	BUTTONDOWN=3
	BUTTONUP=4

	rotary_a = 0
	rotary_b = 0
	rotary_c = 0
	last_state = 0
	direction = 0

	# Initialise rotary encoder object
	def __init__(self,pinA,pinB,button,callback):
		self.pinA = pinA
		self.pinB = pinB
		self.button = button
		self.callback = callback

		GPIO.setmode(GPIO.BCM)
		
		# The following lines enable the internal pull-up resistors
		# on version 2 (latest) boards
		GPIO.setwarnings(False)
		GPIO.setup(self.pinA, GPIO.IN, pull_up_down=GPIO.PUD_UP)
		GPIO.setup(self.pinB, GPIO.IN, pull_up_down=GPIO.PUD_UP)
		GPIO.setup(self.button, GPIO.IN, pull_up_down=GPIO.PUD_UP)

		# For version 1 (old) boards comment out the above four lines
		# and un-comment the following 3 lines
		#GPIO.setup(self.pinA, GPIO.IN)
		#GPIO.setup(self.pinB, GPIO.IN)
		#GPIO.setup(self.button, GPIO.IN)

		# Add event detection to the GPIO inputs
		GPIO.add_event_detect(self.pinA, GPIO.FALLING, callback=self.switch_event)
		GPIO.add_event_detect(self.pinB, GPIO.FALLING, callback=self.switch_event)
		GPIO.add_event_detect(self.button, GPIO.BOTH, callback=self.button_event, bouncetime=200)
		return

	# Call back routine called by switch events
	def switch_event(self,switch):
		if GPIO.input(self.pinA):
			self.rotary_a = 1
		else:
			self.rotary_a = 0

		if GPIO.input(self.pinB):
			self.rotary_b = 1
		else:
			self.rotary_b = 0

		self.rotary_c = self.rotary_a ^ self.rotary_b
		new_state = self.rotary_a * 4 + self.rotary_b * 2 + self.rotary_c * 1
		delta = (new_state - self.last_state) % 4
		self.last_state = new_state
		event = 0

		if delta == 1:
			if self.direction == self.CLOCKWISE:
				# print "Clockwise"
				event = self.direction
			else:
				self.direction = self.CLOCKWISE
		elif delta == 3:
			if self.direction == self.ANTICLOCKWISE:
				# print "Anticlockwise"
				event = self.direction
			else:
				self.direction = self.ANTICLOCKWISE
		if event > 0:
			self.callback(event)
		return


	# Push button up event
	def button_event(self,button):
		if GPIO.input(button): 
			event = self.BUTTONUP 
		else:
			event = self.BUTTONDOWN 
		self.callback(event)
		return

	# Get a switch state
	def getSwitchState(self, switch):
		return  GPIO.input(switch)

# End of RotaryEncoder class