DaniWeb Forum Index > Software Development > C

C RSS

how to detect push buttons

Please support our C advertiser: Programming Forums - DaniWeb Sister Site

•

Join Date: Jun 2007

Posts: 2

Reputation: laugh is an unknown quantity at this point

Solved Threads: 0

laugh

Offline

Newbie Poster

how to detect push buttons

Jun 18th, 2007

Hi..
I'm new in programming microcontroller in c. And I was given an assignment to write a simple program to turn 'ON' and "OFF' the LED by pressing push buttons. The microcontroller i'm using is PIC18F4620. And i'll need 1 LED and 2 push buttons to program this. I have already tried to write the program but it doesnt work. Here is my program:

Help with Code Tags

(Toggle Plain Text)

#include <p18f4620.h>
 
#pragma config OSC = HS
#pragma config WDT = OFF
#pragma config LVP = OFF
 
#define btn_on    PORTBbits.RB4
#define btn_off  PORTBbits.RB5
#define led        PORTAbits.RA0
 
void on(void);
void off(void);
 
void main(void)
{
             TRISA = 0;                  //set Port A(LED) as output
             PORTAbits.RA0 = 0;  //reset LED
    
             while(btn_on != btn_off)        //wait for btn press
    
    if (btn_on = 1)  //btn on pressed
    on();
 
    if (btn_off = 1)    //btn off pressed
    off();
}
 
    void on(void)
    {
              while(!btn_on);        //wait for btn(RB4) released
              PORTAbits.RA0 = 0x0F;  //on LED
    }
    
    void off(void)
    {
             while(!btn_off);         //wait for btn(RB5) released
              PORTAbits.RA0 = 0x00;  //off LED
    }

the underline statement is the one i not sure whether is correct or not. I have being working on this for a week. But still cant get the program run correctly. Hope to get some guide. Thank.

Last edited by Narue; Jun 18th, 2007 at 11:13 am.

•

Join Date: Sep 2004

Posts: 7,730

Reputation: Narue has a reputation beyond repute

Solved Threads: 737

Narue

Offline

Code Goddess

Re: how to detect push buttons

Jun 18th, 2007

>while(btn_on != btn_off) //wait for btn press
I get this tingly sensation that you should be using braces for this loop. That is, of course, if you want both conditional statements to be a part of the loop. If you only care about the first conditional, you're okay.

>if (btn_on = 1) //btn on pressed
Are you really sure you want to assign 1 to btn_on here? This is usually a bug where people mean to use == for comparison.

>if (btn_off = 1) //btn off pressed
Ditto.

Last edited by Narue; Jun 18th, 2007 at 11:14 am.

I'm here to prove you wrong.

•

Join Date: Dec 2006

Posts: 2,033

Reputation: Aia has much to be proud of

Solved Threads: 177

Aia

Offline

Postaholic

Re: how to detect push buttons

Jun 18th, 2007

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
void main(void)
void main(void)

Should be

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
int main( void )
int main( void )

Here's some reading about it.

•

Join Date: Dec 2005

Posts: 5,850

Reputation: Salem has a reputation beyond repute

Solved Threads: 749

Salem

Offline

Void main'ers are DOOMed

Re: how to detect push buttons

Jun 18th, 2007

> void main(void)
Actually, it may be just fine as it is.

> The microcontroller i'm using is PIC18F4620.
This qualifies as a "freestanding" implementation. So long as main, or whatever the documented entry point is, is declared in a manner consistent with that implementation, then it should be good.
http://c-faq.com/ansi/voidmain.html

There's unlikely to be anything in the environment waiting for the result.