Freenove Ultimate Starter Kit

79
Chapter 4 Analog & PWM
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After the program is executed, you'll see that LED is turned from on to off and then from off to on gradually
like breathing.
The following is the program code:
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#include <wiringPi.h>
#include <stdio.h>
#define ledPin 1 //Only GPIO18 can output PWM
int main(void)
{
int i;
if(wiringPiSetup() == -1){ //when initialize wiring failed,print message to screen
printf("setup wiringPi failed !");
return 1;
}
pinMode(ledPin, PWM_OUTPUT);//pwm output mode
while(1){
for(i=0;i<1024;i++){
pwmWrite(ledPin, i);
delay(2);
}
delay(300);
for(i=1023;i>=0;i--){
pwmWrite(ledPin, i);
delay(2);
}
delay(300);
}
return 0;
}
Since only GPIO18 of RPi has hardware capability to output PWM, the ledPin should be defined as 1 and set
its output mode to PWM_OUTPUT based on the corresponding chart for pins.
pinMode(ledPin, PWM_OUTPUT);//pwm output mode
There are two “for” cycles in the next endless “while” cycle. The first makes the ledPin output PWM from 0% to
100% and the second makes the ledPin output PWM from 100% to 0%.
while(1){
for(i=0;i<1024;i++){
pwmWrite(ledPin, i);
delay(2);
}
delay(300);
for(i=1023;i>=0;i--){
pwmWrite(ledPin, i);
delay(2);
}