Smart light program

In this smart light program, we will first read input from the LDR sensor and, based on the input value, we will turn the LED on or off. The program for smart light is described as follows. You can download the SmartLight.cpp program from the Chapter02 folder of this book's GitHub repository: 

#include <iostream>
#include <wiringPi.h>

int main(void)
{

wiringPiSetup();

pinMode(0,OUTPUT); 
pinMode(8,INPUT); 

for(;;)
{
int ldrstate = digitalRead(8); 
if(ldrstate == HIGH) 
{
digitalWrite(0,HIGH); 
}
else
{
digitalWrite(0,LOW); 
}
 }
return 0;
 }

The explanation of the preceding program is as follows:

• Inside the main function, we have set wiringPi pin 8 as the input pin and wiringPi pin 0 as the output pin. 
• Next, in the for loop, using the digitalRead(8) function, we are reading the incoming digital data from the digital pin(D0) of the LDR sensor and storing it inside the ldrstate variable. From the LDR sensor, we will receive HIGH(1) data or LOW(0) data. The ldrstate variable will be HIGH when there is no light and it will be LOW when there is light.
• Next, we will check whether the data inside the ldrstate variable is HIGH or LOW using an if...else condition.
• Using if(ldrstate == HIGH), we are comparing whether the data inside the ldrstate variable is HIGH. If it is HIGH, we are turning the LED on using digitalWrite(0,HIGH). 
• If the ldrstate is LOW, then the else condition will execute and by using digitalWrite(0,LOW), we are turning the LED off. Next, you can click on the Compile button to compile the code and then test it by clicking the Build button.

Now that we understand the SmartLight program, we will explore the concept of Pulse Width Modulation (PWM) and use a library called softPWM to change the brightness of an LED.