Detecting a change in Python loop for RaspberryPi

Question

I have a problem in Python for a RaspberryPi program. In this continuous loop it will detect a change in one of the pins and will then open another pin + request a URL.

This works but the URL is being triggered all the time. So I want to optimize the loop to have the URL request only on change.

If found Dectecting a value change in Python loop but I could not get it to work properly.

Can you help me with this? Thanks in advance! Your help is much appreciated :)

P.S. If the urllib code can be optimized, please let me know. I'm getting to know Python more day-by-day #beginner ;)

#!/usr/bin/env python

import time
import urllib2
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(26, GPIO.IN, GPIO.PUD_UP)
GPIO.setup(24, GPIO.OUT)

GPIO.output(24, GPIO.LOW)

username = "some"
password = "one"

while True:
    if GPIO.input(26):
        GPIO.output(24, GPIO.HIGH)
        password_mgr1 = urllib2.HTTPPasswordMgrWithDefaultRealm()
        top_level_url1 = "http://192.168.x.x/dev/sps/io/VI7/On"
        password_mgr1.add_password(None, top_level_url1, username, password)
        handler1 = urllib2.HTTPBasicAuthHandler(password_mgr1)
        opener1 = urllib2.build_opener(handler1)
        opener1.open(top_level_url1)

    else:
        GPIO.output(24, GPIO.LOW)
        password_mgr2 = urllib2.HTTPPasswordMgrWithDefaultRealm()
        top_level_url2 = "http://192.168.x.x/dev/sps/io/VI7/Off"
        password_mgr2.add_password(None, top_level_url2, username, password)
        handler2 = urllib2.HTTPBasicAuthHandler(password_mgr2)
        opener2 = urllib2.build_opener(handler2)
        opener2.open(top_level_url2)
        time.sleep(5)

GPIO.cleanup()

quamrana · Accepted Answer · 2017-08-08 11:12:32Z

0

I almost never write python code but what about the following (it might have syntax errors but you get the gist)

#!/usr/bin/env python

import time
import urllib2
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(26, GPIO.IN, GPIO.PUD_UP)
GPIO.setup(24, GPIO.OUT)

GPIO.output(24, GPIO.LOW)

username = "some"
password = "one"
lastState = False
while True:
    state = GPIO.input(26)
    if (state != lastState):
        lastState = state
        if state:
            GPIO.output(24, GPIO.HIGH)
            password_mgr1 = urllib2.HTTPPasswordMgrWithDefaultRealm()
            top_level_url1 = "http://192.168.x.x/dev/sps/io/VI7/On"
            password_mgr1.add_password(None, top_level_url1, username, password)
            handler1 = urllib2.HTTPBasicAuthHandler(password_mgr1)
            opener1 = urllib2.build_opener(handler1)
            opener1.open(top_level_url1)

        else:
            GPIO.output(24, GPIO.LOW)
            password_mgr2 = urllib2.HTTPPasswordMgrWithDefaultRealm()
            top_level_url2 = "http://192.168.x.x/dev/sps/io/VI7/Off"
            password_mgr2.add_password(None, top_level_url2, username, password)
            handler2 = urllib2.HTTPBasicAuthHandler(password_mgr2)
            opener2 = urllib2.build_opener(handler2)
            opener2.open(top_level_url2)
            time.sleep(5)

GPIO.cleanup()

edited Aug 8, 2017 at 11:12

quamrana

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answered Aug 8, 2017 at 11:08

Peter

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2 Comments

Racso Over a year ago

Works like a charm! Thanks so much.

Peter Over a year ago

@Racso no problem happy to help!

xyl0o · Accepted Answer · 2017-08-08 11:23:16Z

0

Just add a variable that stores if the value has changed:

# [...]

haschanged = False

while True:
    if GPIO.input(26):
        if haschanged:
            continue
        haschanged = True
        # [...]
    else:
        haschanged = False
        # [...]
# [...]

answered Aug 8, 2017 at 11:23

xyl0o

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