Unwanted multiple presses when using GPIO button press detection

Question

I use this to detect momentary button (connected to GPIO) press :

import RPi.GPIO as GPIO 
GPIO.setmode(GPIO.BCM) 
GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP) 
def my_callback(channel): 
 print channel
GPIO.add_event_detect(18, GPIO.RISING, callback=my_callback, bouncetime=300) 
raw_input()

Even with the debouncing thanks to bouncetime=300, I often get 2 messages instead of just 1 for a single button press.

How to detect properly one button press ?

Answer 1

I hope it's not too late to answer your question; I encountered the same issue and wanted to post the solution I found! What I did was using the buttons and switches introduction on the official Raspberry site and their workaround.

It doesn't use add_event_detect but defines a function (called BtnCheck). What I use looks like this:

#!/usr/bin/env python
import RPi.GPIO as GPIO
import time
# setup everything
GPIO.setmode(GPIO.BOARD)
GPIO.setup(12, GPIO.IN, pull_up_down=GPIO.PUD_UP)
count = 0
prev_inp = 1
# define a function that checks for buttons pressed. The heart of the answer...
def BtnCheck(PinNr):
 global prev_inp
 global count
 inp = GPIO.input(PinNr)
 if ((not prev_inp) and inp):
 count = count + 1
 print "Button pressed"
 print count
 rev_inp = inp
 time.sleep(0.05)
try:
 while True:
 BtnCheck(12)
except KeyboardInterrupt:
 GPIO.cleanup()

• robo: This isn't particularly helpful in that one is probably using the event detection functions to avoid this type of looping in the first place.

Answer 2

I would suggest you use pygame libraries and detect a key press event. It works....

• Bex: How would one do that? And what is the benefit of using pygame before other means of accomplishing this?