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  • Author Author: joetrotter
  • Date Created: Date Created
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need help with pull up on input

I am using the gertboard and wiringPi ,and trying to figure out the buttons. The program reads the low when the pull is pushed, but when not pushed, the input is acting as if it is floating and reading random HIGH and LOW. Im a teacher, new to RaspberryPi, beginner  programmer, and am trying to further my knowledge of C. Any help is appreciated. My code is:

 

#include <wiringPi.h>

#include <stdio.h>

#include <math.h>

#include <time.h>

int main(void)

{

wiringPiSetupGpio();

pinMode(25,INPUT);

pullUpDnControl(25,PUD_UP);

pinMode(17,OUTPUT);

pinMode(24,OUTPUT);  //if these unused i/o left not set up. they follow GPIO 17 for some reason

digitalWrite(24,LOW);

pinMode(23,OUTPUT);

digitalWrite(23,LOW);

pinMode(22,OUTPUT);

digitalWrite(22,LOW);

pinMode(21,OUTPUT);

digitalWrite(21,LOW);

pinMode(18,OUTPUT);

digitalWrite(18,LOW);

pinMode(15,OUTPUT);

digitalWrite(15,LOW);

int x=0;

while(x<20)

{

if (digitalRead(25)==LOW)

{

printf("pushed LED ON, %i\n",x);

digitalWrite(17,HIGH);

while (digitalRead(25)==LOW)

{;}

}

if (digitalRead(25)==HIGH)

{

printf("not pushed LED OFF , %i\n",x);

digitalWrite(17,LOW);

while (digitalRead(25)==HIGH)

{;}

x++;

}

 

}

return 0;

}

 

Parents

  • I'd suggest removing these lines and seeing what happens.

     

      while (digitalRead(25)==LOW)
  {;}


  while (digitalRead(25)==HIGH)
  {;}

     

    These will have you stuck and not contnuing the loop.

     

    As the loop runs it checks if Pin25 is LOW or HIGH and does what it needs to.

     

    A comparison would be sending two pupils to a door and asking one is the Door OPEN, and the other is the Door CLOSED

    versus sending them and telling them to stay while it is OPEN or CLOSED.

     

     

    Outputs should only change when told to.

    So there should be no need to do anything else.

     

     

    Mark

Comment

  • I'd suggest removing these lines and seeing what happens.

     

      while (digitalRead(25)==LOW)
  {;}


  while (digitalRead(25)==HIGH)
  {;}

     

    These will have you stuck and not contnuing the loop.

     

    As the loop runs it checks if Pin25 is LOW or HIGH and does what it needs to.

     

    A comparison would be sending two pupils to a door and asking one is the Door OPEN, and the other is the Door CLOSED

    versus sending them and telling them to stay while it is OPEN or CLOSED.

     

     

    Outputs should only change when told to.

    So there should be no need to do anything else.

     

     

    Mark

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