Raspberry Pi GPIO Interrupts & Configurations- BCM BOARD WiringPi Physical Numbering

Sometimes, it is confusing if you are developing IoT or Robotics logics in Web-Interface, DesktopApp, AndroidApp to access RPi.GPIO. This post will guide you all GPIO configuration modes.

• 1. Physical Numbering: This gives exact PIN numbers starting from 1-40
• 2. BOARD Configuration: This mode was used in earlier model A pi frequently & generally used when you are writing some drivers, libraries at kernel level or in .h files
• 3. WiringPi: This mode is used if you are trying to access GPIO from php or command line http://wiringpi.com/the-gpio-utility/ 
•  
• 4. BCM Configuration: This mode is frequently used from various programming languages specially python codes. BCM GPIO PINS changed from model A to B.

Sensing GPIO input for different types of sensors & switches:

• GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_UP)
• channel = GPIO.wait_for_edge(channel, GPIO_RISING, timeout=5000)

Command-line gpio access:

• gpio readall: Displays all GPIO status
• gpio write <pin> 1/0: Write PIN high/low
• gpio read <pin>: Read PIN status
• Read more: http://wiringpi.com/the-gpio-utility/  

GPIO handling interrupts for infinite loop:

try:
 while 1:
   if GPIO.input(pin):
     print "ON"

   else:
    print "OFF"
    break
except KeyboardInterrupt:
   print "Ctrl+C pressed"

finally:
   GPIO.cleanup()

Read more here: http://raspi.tv/2013/rpi-gpio-basics-3-how-to-exit-gpio-programs-cleanly-avoid-warnings-and-protect-your-pi & https://sourceforge.net/p/raspberry-gpio-python/wiki/Inputs/  

GPIO handling interrupts in PyQt:

• Create another worker class that will contain gpio control function.
• Inherit worker class instance in MainUI.
• On clicked.connect() of qpushbuttons or any signal slots call worker.gpiocontrolfunction()

import sys
import time
from PyQt4 import QtGui, QtCore

class Worker(QtCore.QObject):
    def __init__(self, parent=None):
        QtCore.QObject.__init__(self, parent)

        self.t1 = QtCore.QThread()
        self.moveToThread(self.t1)
        self.t1.start()

    def do_stuff(self):
        while True:
            print 'loop'
            time.sleep(1)

class MainWindow(QtGui.QWidget):
    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)

        self.worker = Worker()

        self.button = QtGui.QPushButton('start', self)
        self.button.clicked.connect(self.worker.do_stuff)  # connect directly with worker's method do_stuff
        #self.button.clicked.connect(lambda: self.worker.do_stuff())  # connect with lambda object containing do_stuff

app = QtGui.QApplication(sys.argv)
main = MainWindow()
main.show()
sys.exit(app.exec_()) 

Read more: https://stackoverflow.com/questions/37008975/update-gui-from-event-in-python-qt & https://stackoverflow.com/questions/25710209/how-to-interrupt-qthread-from-pyqt-gui

GPIO access from PhP for web-interface & home/office automation:

• GPIO.OUT

<?php 
                        system("gpio mode 28 out");
                        if(isset($_POST['off3']))
                        {
                          echo '<img src="images/fan-off.png";                                     exec("gpio write 28 0");    
                        }
                        if(isset($_POST['on3']))
                        {
                            echo '<img src="images/fan-on.gif";
                            exec("gpio write 28 1");
                        }
 ?>

• GPIO.IN

                        system("gpio mode 25 in");
                        exec("gpio read 25",$status);
                        if($status[0]==0)
                            echo '<img src="images/sad-plant.jpg";

• Reload php page automatically

<?php
$page = $_SERVER['PHP_SELF'];
$sec = "2";
?>

GitHub homeautomation project: https://github.com/vsltech/home-automation 

Read how to find Raspberry Pi IP without HDMI display: http://www.vslcreations.com/2018/01/how-to-find-raspberry-pi-ip-without.html

Read how to start image processing in Raspberry Pi: http://www.vslcreations.com/2017/06/how-to-start-image-processing-for.html

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