RPI.GPIO Help

John McKenzie davros at bellaliant.net
Sun Aug 16 21:40:01 CEST 2015


 Hello, all. I am hoping some people here are familiar with the RPi.GPIO 
python module for the Raspberry Pi.

 Very new to Python and electronics. Not to computing in general though. 
I posted for help about accepting key presses and then discovered that 
wiring up buttons directly to the Pi was 1/50th as difficult as I thought 
it would be so I am going a different route than keyboard emulation and 
needing GUI toolkits, etc.

 However, I am getting error messages with RPi.GPIO.

 I have three buttons, Red, Yellow and Blue in colour, attached to the 
Pi. The eventual goal is to have pressing one button result in changing 
the colour of an LED lightstrip to that colour and the Pi record how long 
the strip spent as each colour.

 For development purposes I have the controls near me and my desktop 
computer, and the Pi networked to this computer. For now I have each 
button press result in a print statement. When I get this working I will 
replace the print statements with the code to change colours on the LED 
strip using the Blinkstick module.

 This is the basic test code.


import atexit
import time
from blinkstick import blinkstick
import RPi.GPIO as GPIO  

led = blinkstick.find_first()
colour = 0
timered = 0
timeyellow = 0
timeblue = 0
timestamp = time.strftime("%H:%M:%S")


GPIO.setmode(GPIO.BCM)
GPIO.setup(22, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)  
GPIO.setup(24, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) 




def red_button(channel):
    colour = 1
    print "Red Button Pressed"
    while colour == 1:
        timered += 1

def yellow_button(channel):
    colour = 2
    print "Yellow Button Pressed"
    while colour == 2:
        timeyellow += 1

def blue_button(channel):
    colour = 3
    print "Blue Button Pressed"
    while colour == 3:
        timeblue += 1

while True:
    GPIO.add_event_detect(22, GPIO.RISING, callback=red_button, 
bouncetime=200)
    GPIO.add_event_detect(23, GPIO.RISING, callback=yellow_button, 
bouncetime=200)
    GPIO.add_event_detect(24, GPIO.RISING, callback=blue_button, 
bouncetime=200)


def exit_handler():
    print '\033[0;41;37mRed Team:\033[0m ', timered
    print '\033[0;43;30mYellow Time:\033[0m ', timeyellow
    print '\033[0;44;37mBlue Time:\033[0m ', timeblue
    flog = open('flag1log.text', 'a')
    flog.write(timestamp + '\n' + 'Red Team: ' + str(timered) + '\n' + 
'Yellow Team: ' + str(timeyellow) + '\n' + 'Blue Team: ' + str(timeblue) 
+ '\n')
    flog.close()
atexit.register(exit_handler)
GPIO.cleanup()



 This results in the error message "RuntimeError: Conflicting edge 
detection already enabled for this GPIO channel".  Running GPIO.cleanup() 
in the interpreter results in a message stating the GPIO pins are not 
assigned and there is nothing to cleanup.
 
  Removing line 40, the while True: line, removes the error, but the 
program does not sit and wait waiting for a button press, it just runs 
and ends a second later.
  
   There are other things this script will need, but this is the core 
function  that I need to get working -pressing a button does what I want 
and the script keeps running so I can press another button if I want. If 
are familiar with the RPi.GPIO or see a more general Python mistake that 
could be affecting everything know I would appreciate your help. Thanks.
   


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