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Python help with GPIO

rcayot

Okay, I guess it is time to ask for help.  I have learned how to breadboard up a set of traffic lights, a button and a buzzer.  I can get them all to work with simple python programs.  Now I want to interrupt the normal light sequence when the button is pushed.  I can even get a detect event to work.  What I do not seem to be able to do is condition the "if" or "while" loop for the lights on the event. 

 

I have a callback and it seems to work, so I can print the status of the "button is pressed" but I cannot pass it as "true" to the loop.  I suspect it may be that when defining "btnpushed" it is local to only the callback loop?

 

i can self learn, but most of the tutorials I see are very single topic context, like what is a while loop or what is an if loop.  Any pointers to a good example of using these functions would be great!

 

i hope this is clear.

 

Roger Ayotte

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  • 0

    okay, here is the code

     

    import RPi.GPIO as GPIO


from time import sleep
from signal import pause
GPIO.setmode(GPIO.BCM)


GPIO.setup(25, GPIO.OUT, initial=GPIO.LOW)  # red LED
GPIO.setup(12, GPIO.OUT, initial=GPIO.LOW)  # yellow LED
GPIO.setup(20, GPIO.OUT, initial=GPIO.LOW)  # green LED

btnpushed = 0

GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_UP)
def cb1(channel):
    btnpushed == 1
    print(btnpushed)
   
GPIO.add_event_detect(26, GPIO.FALLING, callback=cb1, bouncetime=300)

try:
    while btnpushed == 0:
        GPIO.output(20, GPIO.HIGH)  # green on
        sleep(5)  #
        GPIO.output(20, GPIO.LOW)  # green off
        sleep(0.01)
        GPIO.output(12, GPIO.HIGH)  # yellow on
        sleep(2)
        GPIO.output(12, GPIO.LOW)  # yellow off
        GPIO.output(25, GPIO.HIGH)  # red on
        sleep(5)
        GPIO.output(25, GPIO.LOW)  # red off
        pause


except KeyboardInterrupt:
    GPIO.cleanup((25, 26, 12, 20))
GPIO.cleanup((25, 26, 12, 20))

     

    what I am trying to do is use the boolean 1, or 0 for btnpushed to interrupt the light loop.  whenever I push the button, I get a zero printed.  and the light sequence keeps going.  Will try the 'not' later.

  • 0 in reply to fmilburn

    I happened to be trying that, it works when only = instead of ==

     

    I added a print statement after btnpushed = 0 and at the start of the program it prints 0, and when I press the button, it prints 1 but on every case the lights keep cycling.

     


    Roger

  • 0 in reply to fmilburn

    fixed code for == issue.

     

    import RPi.GPIO as GPIO
from time import sleep
from signal import pause
GPIO.setmode(GPIO.BCM)


GPIO.setup(25, GPIO.OUT, initial=GPIO.LOW)  # red LED
GPIO.setup(12, GPIO.OUT, initial=GPIO.LOW)  # yellow LED
GPIO.setup(20, GPIO.OUT, initial=GPIO.LOW)  # green LED


btnpushed = 0
print(btnpushed)
GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_UP)


def cb1(channel):
    btnpushed = 1
    print(btnpushed)


GPIO.add_event_detect(26, GPIO.FALLING, callback=cb1, bouncetime=300)


try:
    while btnpushed == 0:
        GPIO.output(20, GPIO.HIGH)  # green on
        sleep(5)   #
        GPIO.output(20, GPIO.LOW)  # green off
        GPIO.output(12, GPIO.HIGH)  # yellow on
        sleep(2)
        GPIO.output(12, GPIO.LOW)  # yellow off
        GPIO.output(25, GPIO.HIGH)  # red on
        sleep(5)
        GPIO.output(25, GPIO.LOW)  # red off
        pause


except KeyboardInterrupt:
    GPIO.cleanup((25, 26, 12, 20))

GPIO.cleanup((25, 26, 12,

     

     

    still prints 0 and does not stop while btnpushed == 0: loop

     

    Roger

Reply
  • 0 in reply to fmilburn

    fixed code for == issue.

     

    import RPi.GPIO as GPIO
from time import sleep
from signal import pause
GPIO.setmode(GPIO.BCM)


GPIO.setup(25, GPIO.OUT, initial=GPIO.LOW)  # red LED
GPIO.setup(12, GPIO.OUT, initial=GPIO.LOW)  # yellow LED
GPIO.setup(20, GPIO.OUT, initial=GPIO.LOW)  # green LED


btnpushed = 0
print(btnpushed)
GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_UP)


def cb1(channel):
    btnpushed = 1
    print(btnpushed)


GPIO.add_event_detect(26, GPIO.FALLING, callback=cb1, bouncetime=300)


try:
    while btnpushed == 0:
        GPIO.output(20, GPIO.HIGH)  # green on
        sleep(5)   #
        GPIO.output(20, GPIO.LOW)  # green off
        GPIO.output(12, GPIO.HIGH)  # yellow on
        sleep(2)
        GPIO.output(12, GPIO.LOW)  # yellow off
        GPIO.output(25, GPIO.HIGH)  # red on
        sleep(5)
        GPIO.output(25, GPIO.LOW)  # red off
        pause


except KeyboardInterrupt:
    GPIO.cleanup((25, 26, 12, 20))

GPIO.cleanup((25, 26, 12,

     

     

    still prints 0 and does not stop while btnpushed == 0: loop

     

    Roger

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