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Raspberry Pi RPi.GPIO Error with Handled Callback

I am stuck with the wait_for_edge function in a Python RPi package . I added a few event detections for gpio to crash, and everything works fine as long as the callback functions do not contain a command, e.g.

 os.system("mpc pause")

Then the script crashes with the error message: "RunetimeError: error # 5, waiting for the edge" Does anyone know what this error message wants to say? Or where can I look for such things?

To be specific, this code works:

def next(channel):
    print "In next"

GPIO.add_event_detect(buttonnext,GP.FALLING,callback=next,bouncetime=200)

os.system("mpc play")

try:
    GPIO.wait_for_edge(buttonstop, GP.FALLING)
    os.system("mpc stop")
except KeyboardInterrupt:
    GPIO.cleanup()
    os.system("mpc stop")
GPIO.cleanup()

But this code does not:

def next(channel):
    print "In next"
    os.system("mpc next")

GPIO.add_event_detect(buttonnext,GP.FALLING,callback=next,bouncetime=200)

os.system("mpc play")
try:
    GPIO.wait_for_edge(buttonstop, GP.FALLING)
    os.system("mpc stop")
except KeyboardInterrupt:
    GPIO.cleanup()
    os.system("mpc stop")
GPIO.cleanup()

Failure to press a button connected to a port stop button.

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1 answer

Super hacky, os.system, , , , , .

def next(channel):
    print "In next"
    os.system("mpc next")
    GPIO.remove_event_detect(buttonnext)
    GPIO.add_event_detect(buttonnext,GP.FALLING,callback=next,bouncetime=200)
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