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125 Chapter 10 Photoresistor & LED █ www.freenove.com
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Code
The code of this project is identical with the one in last chapter logically.
C Code 10.1.1 Nightlamp
First observe the project result, and then analyze the code.
1.
Use cd command to enter 010.1.1_Nightlamp directory of C code.
cd ~/Freenove_Ultimate_Starter_Kit_for_Raspberry_Pi/Code/C_Code/10.1.1_Nightlamp
2. Use following command to compile “Nightlamp.c” and generate executable file “Nightlamp”.
gcc Nightlamp.c -o Nightlamp -lwiringPi -lpthread
3. Then run the generated file “Nightlamp”.
sudo ./Nightlamp
After the program is executed, when you cover the photosensitive resistance or make a flashlight toward the
photoresistor, the brightness of LED will be enhanced or weakened. And the terminal window will print out
the current input voltage value of PCF8591 AIN0 pin and the converted digital quantity.
The following is the program code:
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#include <wiringPi.h>
#include <pcf8591.h>
#include <stdio.h>
#include <softPwm.h>
#define address 0x48 //pcf8591 default address
#define pinbase 64 //any number above 64
#define A0 p 0
#define A1 p 1
#define A2 p 2
#define A3 p 3
#define ledPin 0
int main ( void ){
int value ;
float voltage ;
if ( wiringPiSetup () == - 1 ){ //when initialize wiring failed,print message to screen
printf ( "setup wiringPi failed !" );
return 1 ;
}
softPwmCreate ( ledPin , 0 , 100 );
pcf8591Setup ( pinbase , address );
while ( 1 ){
value = analogRead ( A0 ); //read A0 pin
softPwmWrite ( ledPin , value * 100 / 255 );
voltage = ( float ) value / 255.0 * 3.3 ; // calculate voltage
printf ( "ADC value : %d ,\tVoltage : %.2fV\n" , value , voltage );