Python help with GPIO

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.

yes, when I set btnpushed to 1, the while btnpushed == 0 does not run.

when set to 0 it runs, and when I get an event that sets it to 1 the while btnpushed = 0 still runs!

Roger

Do you intend for line 17 to have == instead of =

Hi Roger,

I've not looked at all of the code, but you've got a bug that really ought to have generated a warning in any other language..

line 17 has a double equals, which needs to be a single equals (assuming you wish to set that variable)

Also, anything you do in that def will be local.. assuming that's what you want? Otherwise you need to declare it as global remember, as mentioned in posts earlier..

Roger,

In your code you are confusing the meaning  of "=" and "==".  In the statement inside of the callback (cb1) you have a statement "btnpushed == 1".  This should be "btnpushed = 1".  The first is a test, comparing btnpushed to 1, where the other is an assignment setting btnpushed to 1.

Good luck!
Gene

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

Good catch!

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

That article is quoting from Wikipedia. In any event, the Wikipedia examples for both C and Python are just examples of passing functions as arguments, since it is all executing in a single thread. A real callback would need to execute in a different thread if it was to be able to ever work asynchronously. (I guess! I'm not an expert..).

well, the single = is what is correct there, but then after that you still have to deal with the issue that the callback comes in on a separate thread from the main thread, and its only a 1 in the thread that is the callback, not in main.