RisingFallingEncoder.py

from __future__ import division
import RPi.GPIO as GPIO
from time import sleep
import math

GPIO.setmode(GPIO.BOARD)
GPIO.setup(11, GPIO.IN)
GPIO.setup(12, GPIO.IN)

countRisLeft=0
countFallLeft=0
countRisRight=0
countFallRight=0

def my_callback(channel):
    global countRisLeft
    global countFallLeft
    global countRisRight
    global countFallRight

    if GPIO.input(11):
        countRisRight=countRisRight+1
        print "Rising edge detected on 11"
        return countRisRight

    else:
        countFallRight=countFallRight+1
        print "Falling edge detected on 11"
        return countFallRight

    if GPIO.input(12):
        countRisLeft=countRisLeft+1
        print "Rising edge detected on 12"

    else:
        countFallLeft=countFallLeft+1
        print "Falling edge detected on 12"

GPIO.add_event_detect(11, GPIO.BOTH, callback=my_callback)
GPIO.add_event_detect(12, GPIO.BOTH, callback=my_callback)

distanceForATick=2*math.pi*3.35/20
print "distanceForATick: ",distanceForATick

try:
    sleep(30)
    print "RisingLeft",countRisLeft
    print "FallingLeft", countFallLeft
    TotalDistanceFromLeft=distanceForATick*max(countRisLeft,countFallLeft)
    print "TotalDistanceFromLeft:", TotalDistanceFromLeft

    print "RisingRight",countRisRight
    print "FallingRight", countFallRight
    TotalDistanceFromRight=distanceForATick*max(countRisRight,countFallRight)
    print "TotalDistanceFromRight:", TotalDistanceFromRight

finally:
    GPIO.cleanup()