====== Nightlamp ======

**//The Circuit://**
{{:hpc0:nightlamp.jpg?nolink|}}

**//The Code://**

<code c>
  1 /********************************************************************** 
  2 * Filename    : Nightlamp.cpp                            
  3 * Description : Photoresistor control LED                
  4 * Author      : www.freenove.com                         
  5 * modification: 2020/03/09                               
  6 **********************************************************************/ 
  7 #include <wiringPi.h>                                    
  8 #include <stdio.h>                                       
  9 #include <softPwm.h>                                     
 10 #include <ADCDevice.hpp>                                 
 11                                                          
 12 #define ledPin 0                                         
 13                                                          
 14 ADCDevice *adc;                                      // Define an ADC Device class object 
 15                                                          
 16 int main(void){                                          
 17     adc = new ADCDevice();                           //Tells us what hardware we are using
 18     int   value;                                     //Used for calculating voltage
 19     float voltage;                                   //Stores the voltage 
 20     printf("Program is starting ... \n");                
 21     //check to see what ADC device we have               
 22     if(adc->detectI2C(0x48)){                        // is it the pcf8591.
 23         delete adc;                                  // Make certain adc is empty
 24         adc = new PCF8591();                         // store what device we have
 25     }                                                    
 26     else if(adc->detectI2C(0x4b)){                   // is it the ads7830
 27         delete adc;                                  // Make certain adc is empty
 28         adc = new ADS7830();                         // store what device we have.
 29     }                                                    
 30     else{                                                
 31         printf("No correct I2C address found, \n"        
 32         "Please use command 'i2cdetect -y 1' to check the I2C address! \n"
 33         "Program Exit. \n");                             
 34         return -1;                                       
 35     }                                                    
 36     wiringPiSetup();                                 //Setup the board
 37     softPwmCreate(ledPin,0,100);                         
 38     while(1){                                            
 39         value   = adc->analogRead(0);                //read analog value of first pin
 40         softPwmWrite(ledPin,value*100/255);              
 41         voltage = (float)value / 255.0 * 3.3;        // calculate voltage
 42         printf("ADC value : %d  ,\tVoltage : %.2fV\n",value,voltage);                                       
 43         delay(100);                                      
 44     }                                                    
 45     return 0;                                            
 46 }
</code>

This project is very similar to the [[hpc0:softlight|Softlight]] project with the only key changes being that we swapped out the potentiometer with a photo-resistor. This difference allows the LED to receive a different amount of voltage depending on how much light the photo-resistor receives. The more light the LED gets the dimmer it gets; the less light the LED gets the brighter it gets. As for the code I aligned all the comments, changed up what the comments said in regards to new hardware, added a comment about the conditional, and made it so that the variables were declared outside of the loop.