Reading a GPIO Switch in C language

[ccurran689]

I know I must be doing something stupid here but I cant seem to find a solution, I am trying to have a simple switch in my circuit. I have made a simple switch programme to see where my issue is with no avail;

#include <stdio.h>
#include <wiringPi.h>

int main (void)
{
wiringPisetup () ;
pinMode (4, INPUT) ;
if (4==1) {
printf ("button pressed");
}
return 0;
}

I have one wire connected to one side of button going to gpio 23 ( WiringPi pin 4) and the other going to ground, nothing is happening.

[rpdom]

Code: Select all

if (4==1) {

What are you trying to do here - test if 4 equals 1? Well, it won't ever (except in some really weird maths;) ).
Shouldn't you have something to read the pin value in there?
Something like

Code: Select all

if ( didgitalRead(4) == 1 ) {

[PeterO]

Note that because there is a "switch" statement in the C language, your thread title is very ambiguous. !
PeterO

[ame]

Note that because there is a "switch" statement in the C language, your thread title is very ambiguous. !
PeterO

Did you report the post? There is an option to specify that the title is ambiguous or misleading.

[ame]

Anyway, back to the problem at hand.

OP, do you have a pullup attached to your button? If not, you should turn on the GPIO pullup in your code:
https://projects.drogon.net/raspberry-p ... functions/

Also, double-check the pin number against the physical pin.

[PeterO]

Note that because there is a "switch" statement in the C language, your thread title is very ambiguous. !
PeterO

Did you report the post? There is an option to specify that the title is ambiguous or misleading.

Since rpdom had provided the answer I didn't think it was worth reporting but was worth pointing out it was ambiguous.
PeterO

[GerardWassink]

Anyway, back to the problem at hand.

OP, do you have a pullup attached to your button? If not, you should turn on the GPIO pullup in your code:
https://projects.drogon.net/raspberry-p ... functions/

Also, double-check the pin number against the physical pin.

Neither of these actions will make (4 == 1)...

And in any case, the value of the pin should first be read, otherwise you can test all you want and it will never be what you expect.

And remember:

"Computers do what you tell them, not necessarily what you expect..."

[ame]

Anyway, back to the problem at hand.

OP, do you have a pullup attached to your button? If not, you should turn on the GPIO pullup in your code:
https://projects.drogon.net/raspberry-p ... functions/

Also, double-check the pin number against the physical pin.

Neither of these actions will make (4 == 1)...

And in any case, the value of the pin should first be read, otherwise you can test all you want and it will never be what you expect.

And remember:

"Computers do what you tell them, not necessarily what you expect..."

Yeah. My bad. Oh well.

[PeterO]

Anyway, back to the problem at hand.

OP, do you have a pullup attached to your button? If not, you should turn on the GPIO pullup in your code:
https://projects.drogon.net/raspberry-p ... functions/

Also, double-check the pin number against the physical pin.

Neither of these actions will make (4 == 1)...

However both things are useful advice and need to be correct.
PeterO

[ccurran689]

Thanks very much got it all sorted, I had tried that before but must of mucked it up somehow. Doing an engineering project and have been left a bit blind for the code sorry about the silly questions!