switch.py

#!/usr/bin/python3

import os
import time
import RPi.GPIO as GPIO

"""
A class for the use of mechanical switches connected to the Raspberry Pi.
Switches need to be pulled down (via external pull down resistor or
by using the pull down functionality of the microcontroller). 
This class provides:
- software debounce (no chattering)
- execution of different functions on ON / OFF
"""
# - - - - - - - - - - - - - - - - 
# - - - -  SWITCH CLASS - - - - -
# - - - - - - - - - - - - - - - -
class Switch:
    def __init__(self, pin, switchOnFun, switchOffFun):
        self.pin = pin
        self.switchOnFun = switchOnFun
        self.switchOffFun = switchOffFun
        self.isOn = False 
        self.lastHighTime = 0
        self.SwitchOffTime = 100 # switch turns off after input was low for at least x ms

    def update(self):
        switchStatus = GPIO.input(self.pin)
        if switchStatus and not self.isOn:
            # Trigger on positive flank of Input Signal
            self.isOn = True
            self.switchOn()

        elif not switchStatus and self.isOn:
            # We get in here when the switch gets switched off
            if self.lastHighTime + self.SwitchOffTime < self.getTimeStamp():
                self.isOn = False
                self.switchOff()

        elif switchStatus and self.isOn:
            # Reset last hight Time
            self.lastHighTime = self.getTimeStamp()

    def getTimeStamp(self):
        # returns the current TimeStamp in millisecs
        return int(time.time()*1000)

    def switchOn(self):
        print("pin {0} ON".format(self.pin))
        self.switchOnFun()

    def switchOff(self):
        print("pin {0} OFF".format(self.pin))
        self.switchOffFun()