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.

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

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

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.

rcayot  wrote:

 

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

That's because every variable you're modifying in that def block is _local_. You need to define it as global.

yes? using btnpushed as global worked as far as getting the loop interrupted?

Now back to work on the rest of it!

Thanks all who helped!

Roger Ayotte

yes? using btnpushed as global worked as far as getting the loop interrupted?

Now back to work on the rest of it!

Thanks all who helped!

Roger Ayotte

Roger,

I would assume that you will also need an GPIO.add_event_detect(26, GPIO.FALLING, callback=cb1, bouncetime=300) statement to detect GPIO.RISING to clear btnpushed in order to get your loop running again.

Thanks, I was wondering how I was going to do that!

roger