Question

Questions 3 Write a Python program that implements the following functionality: 1. Makes an LED blink. 2. Then, on a push of a button the blinking stops. 3. Then, on another push of a button the blinking starts again 4. The behavior of steps 2 and 3 keeps repeating whenever the button is pushed. In writing your program, you should use a class, call it Blinkclass, that helps in making the LED blink or not. Connect the needed circuit using Raspberry Pi (RP) board and a bread board.

Answer 1

1. Python program to make LED blink

import RPi.GPIO as GPIO    # Import Raspberry Pi GPIO library
from time import sleep     # Import the sleep function from the time module


GPIO.setmode(GPIO.BOARD)    # Use physical pin numbering

led = 18     #Physical Pin 18 (GPIO24) and LED is connected to GPIO24

# Set pin 18 to be an output pin                                    
# it also sets initial value to low (off)
GPIO.setup(18, GPIO.OUT, initial=GPIO.LOW)

while True:
 GPIO.output(18, GPIO.HIGH)         # Turn on
 sleep(2)                          # Sleep for 2 seconds
 
GPIO.output(18, GPIO.LOW)          # Turn off
sleep(2)                          # Sleep for 2 seconds

2 and 3 : Python program to make LED on and off using push button

Upto here the LED is blinking with a delay of 2 seconds.

#LED is already connected to GPIO24 of Raspberry Pi.

# Connect the push button to Raspberry Pi GPIO on GPIO23.

# pin which is connected to push-button will be an input pin as it will read the data from the button.

# pin connected to LED is an output pin

import RPi.GPIO as GPIO

import time

button = 16
led = 18

def setup():
GPIO.setmode(GPIO.BOARD)
GPIO.setup(button, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(led, GPIO.OUT)

def loop():
while True:
button_state = GPIO.input(button)
if button_state == False:
GPIO.output(led, True)
print('Button Pressed...')
while GPIO.input(button) == False:
time.sleep(0.2)
else:
GPIO.output(led, False)

def endprogram():
GPIO.output(led, False)
GPIO.cleanup()

if __name__ == '__main__':
  
setup()
  
try:
loop()
  
except KeyboardInterrupt:
print 'keyboard interrupt detected'
endprogram()