Question

Write a C program to blink two LEDs connected to Raspberry pi. One must blink at a rate of 1 Hz and the other at a rate of 2 HZ.

Answer 1

Here our task is to blink 2 Led at rate of 1 KHz and 2 KHz

In order program this in raspberry pi we have to include wiring.pi libraray to Raspberry Pi .After successful installation of the library file you can code it in any available C IDE such as geany etc..

Things to consider

• We have to define a varaible called led which stores the gpio pin number at which Led is connected.Make the Led pin as OUTPUT
• We can implement the blink by using digital write() and delay() functions
• total delay(on time +off time) for each led can be findout using formula

delay= 1 frequency

For first led

delay=1 1000 Hz = 1ms

so on time = 0.5 ms =500 micro seconds

off time =0.5 ms =500 micro seconds

For led 2

delay=1 2000 Hz = 0.5ms

so on time = 0.25 ms =250 micro seconds

off time =0.25ms =250 micro seconds

CODE

(please read all comments for better understanding of the program)

I am also attching a text version of the code in case you need to copy paste

#include <wiringPi.h> //including wiringpi file from library
#include <stdio.h>

#define Led1 0 // led which blink at 1 KHz rate at pin 0
#define Led2 1 // led which blink at 2 KHz rate at pin 1

int main() {

pinMode(Led, OUTPUT);
while(1) { // a loop having delay of 1 millisecond (1 millisec=1000 micro sec)
  
digitalWrite(Led1, HIGH); //turning on led 1 at beginning of loop
digitalWrite(Led2, HIGH); //turning on led 2 at beginning of loop
  
delayMicroseconds(250);   //delay of 250 microseconds         
digitalWrite(Led2, LOW); //led2 off (2khz led)
delayMicroseconds(250);
digitalWrite(Led1, LOW); //turning on off led 1 ( so it blink 1 times in loop (1 ms))
digitalWrite(Led2, HIGH); //led 2 on again
delayMicroseconds(250);
digitalWrite(Led2, LOW); //led 2 off (so that it blink 2 times in a loop(1 ms)
delayMicroseconds(250);
  
}
return 0;
}