Hands on Raspberry Hardware Solutions

Controlling an LED via GPIO

Flashing the LED 10 times using a for-loop construct.

import wiringpi
from time import sleep

class Led(object):
  def __init__(self):
    self.pinNumber = 23
    wiringpi.wiringPiSetupGpio()    # Use GPIO numbering
    wiringpi.pinMode(self.pinNumber, 1)        # Set LED pin to 1 ( OUTPUT )
    self.off()

  def on(self):
    self.set_state(True)

  def off(self):
    self.set_state(False)

  def set_state(self, state):
    self.isOn = state
    wiringpi.digitalWrite(self.pinNumber, state)   # Write 0 ( LOW ) to LED pin

  def get_state(self):
    return self.isOn

# Create an object of type Led
led = Led()

for i in range(0,10):
  print("Setting LED on")
  led.on()
  sleep(1)
  print("Setting LED off")
  led.off()
  sleep(1)

print("Done")

Using an LDR as a switch on the Raspberry Pi's GPIO Pins

Reading the LDR in an endless loop. Delay is necessary otherwise the loop would iterate way too fast for us to follow.

import wiringpi
from time import sleep

class LDR(object):
  def __init__(self):
    self.pinNumber = 24
    wiringpi.wiringPiSetupGpio()    # Use GPIO numbering
    wiringpi.pinMode(self.pinNumber, 0)        # Set LDR pin to 0 ( INPUT )

  def get_state(self):
    return wiringpi.digitalRead(self.pinNumber)

# Create an object of LDR
switch = LDR()

while True:
  # Get the state of the LDR
  print("State = " + str(switch.get_state()))
  sleep(0.5)

print("Done")

Combining the LED and the LDR switch

Reading the LDR in an endless loop and turning the LED on accordingly

import wiringpi
from time import sleep

class LDR(object):
  def __init__(self):
    self.pinNumber = 24
    wiringpi.wiringPiSetupGpio()    # Use GPIO numbering
    wiringpi.pinMode(self.pinNumber, 0)        # Set LDR pin to 0 ( INPUT )

  def get_state(self):
    return wiringpi.digitalRead(self.pinNumber)

class Led(object):
  def __init__(self):
    self.pinNumber = 23
    wiringpi.wiringPiSetupGpio()    # Use GPIO numbering
    wiringpi.pinMode(self.pinNumber, 1)        # Set LED pin to 1 ( OUTPUT )
    self.off()

  def on(self):
    self.set_state(True)

  def off(self):
    self.set_state(False)

  def set_state(self, state):
    self.isOn = state
    wiringpi.digitalWrite(self.pinNumber, state)   # Write 0 ( LOW ) to LED pin

  def get_state(self):
    return self.isOn

# Create an object of LED
led = Led()

# Create an object of LDR
switch = LDR()

while True:
  # Get the state of the LDR
  state = switch.get_state()
  print("State = " + str(state))
  led.set_state(state)
  sleep(0.5)

print("Done")