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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 Comment Children
  • in reply to clem57

    Hey Clem,

    thanks for the fast reply. I had ground connected to the four buffered inputs at the top of the gertboard trying to keep LED's 9-12 off. i could have set B9-12 as outputs and set them LOW , but I didn't have enough straps. I guess I don't really understand how those BUF inputs work. I pulled the jumpers out and the program worked as expected. Is there any other way than setting the GPIO as outputs to keep unwired LED's from following other LED's?

     

    Sorry to have bothered you. I love the RaspPi's and excited to dig in and learn. Are there any workshops or classes that i could take that would shorten my learning curve on the RaspPi with C. I'm in the United States. My class has programmed the LEGO Mindstorm Robots in C with RobotC from Caregie Mellon Univ. and have studied analog and digital circuits for a semester. I'm trying to connect the programming, electronics, and peripherals all together.

     

    Thanks again

    Joe Trotter