Electronic Circuits and Projects Forum

30th November 2009 05:01 AM

Hi all,

I am trying to set up a simple "if button is pressed, turn on led1 and turn off led2" and vice versa circuit. But for the life of me I can't get it to work properly.

I am using a pic16f690 chip with the lpc board and the pickit2.

What happens is RC0 led is lit unless I push the button(RA3). RA1 led stays off. I must be doing the if else statement wrong, but everything looks good.

My code looks like this:

#include <pic.h>

void init(void)
{
TRISA=0x8; // set RA3 as input
TRISC=0x00; // set PORTC as outputs
ANSEL=0; // set ports to digital
PORTC=0; // turn off all leds
}

void main(void)
{
init(); // initialize I/O ports
while(1) // loop forever
{

if(RA3==0) // if button is pressed
{RC0=1; // turn on led 0
RC1=0;} // turn off led 1

else // if button is not pressed
{RC1=1; // turn on led 1
RC0=0;} // turn off led 0

}
}

Thanks in advance

30th November 2009 05:19 AM

This may be a RMW problem. Try changing it to,

Code :

    if(RA3==0)
        PORTC=0x01;
    else
        PORTC=0x02;

Edit, you do have JP5 on don't you?

Mike.

30th November 2009 05:37 AM

Hi Pommie,

I do have JP5 on. I changed the code to your advice and the results are the same. RC0 led stays on unless I push the button. Then it turns off. RC1 never comes on.

Just to be sure I am doing things right: I wrote and built the program in mplab. I then exported with config files to a file, and loaded that file with the pickit2 loader.

I'll also post the new code with your changes.

#include <pic.h>

void init(void)
{
TRISA=0x8; // set RA3 as input
TRISC=0x00; // set PORTC as outputs
ANSEL=0; // set ports to digital
PORTC=0; // turn off all leds
}

void main(void)
{
init(); // initialize I/O ports
while(1) // loop forever
{
if(RA3==0)
{PORTC=0x01;}
else
{PORTC=0x02;}

}
}

30th November 2009 06:22 AM

If I change it to:

if(RA3==1)
{PORTC=0x01;}
else
{PORTC=0x02;}

then RA1 led comes on, unless I push the button.

Any help is most appreciated,

Edit: I'm also getting a warning when I build, is this a concern?

Executing: "C:\Program Files\HI-TECH Software\PICC\PRO\9.65\bin\picc.exe" -q -g --asmlist --chip=16F690 "--errformat=Error [%n] %f; %l.%c %s" "--msgformat=Advisory[%n] %s" "--warnformat=Warning [%n] %f; %l.%c %s" -P --char=unsigned --pass1 "C:\Program Files\Microchip\Lessons\c test\ok.c"
Executing: "C:\Program Files\HI-TECH Software\PICC\PRO\9.65\bin\picc.exe" -q -g --asmlist --chip=16F690 "--errformat=Error [%n] %f; %l.%c %s" "--msgformat=Advisory[%n] %s" "--warnformat=Warning [%n] %f; %l.%c %s" -P --char=unsigned -ook1.cof -mok1.map ok.p1

30th November 2009 06:28 AM

Do you have JP1 and JP2 on as well? If you do then I have now idea why it's not working. Maybe someone with an LPC board could help.

Mike.

30th November 2009 07:05 AM

I do have JP1 and JP2 installed.

I don't understand. With the following code, why is RC1 on when the switch isn't pressed? And off when it is?

if(RA3==1)
{PORTC=0x01;}
else
{PORTC=0x02;}

30th November 2009 07:11 AM

The instruction if(RA3==1) will be true if the button isn't pressed as the pin is tied to 5V via a resistor. So when the button isn't pressed the PORTC=0x01 should be executed, so, RC0 should be on and RC1 should be off.

Are you able to use a debugger?

Mike.

30th November 2009 08:34 AM

shouldnt it be something like PORTA.RA3 ?

30th November 2009 09:58 AM

Originally Posted by treefort

Hi Pommie,

I do have JP5 on. I changed the code to your advice and the results are the same. RC0 led stays on unless I push the button. Then it turns off. RC1 never comes on.

Just to be sure I am doing things right: I wrote and built the program in mplab. I then exported with config files to a file, and loaded that file with the pickit2 loader.

I'll also post the new code with your changes.

Edit: Also, do you have MCLRDIS in your __CONFIG statement?

#include <pic.h>

void init(void)
{
TRISA=0x8; // set RA3 as input
TRISC=0x00; // set PORTC as outputs
ANSEL=0; // set ports to digital
PORTC=0; // turn off all leds
}

void main(void)
{
init(); // initialize I/O ports
while(1) // loop forever
{
if(RA3==0)
{PORTC=0x01;}
else
{PORTC=0x02;}

}
}

I would suggest you turn off the comparators on the 16F690.

30th November 2009 10:10 AM

Also, do you have MCLRDIS in your __CONFIG statement?

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