Help with code, button

[xobx]

When I give PORTA.1 +5V, LED1 dosent shine..

Whats wrong with my code?

LED1 var PORTB.1
PRESS var PORTA.1

loop:

If press = 1 then       
            high led1   
            else
            low led1   
            endif      
            goto loop   
            end

[mackrackit]

Does your PIC have ADC?
If it does...
http://www.picbasic.co.uk/forum/showthread.php?t=562

http://www.picbasic.co.uk/forum/showthread.php?t=561

[xobx]

I dont know its a PIC16F648A

[mackrackit]

According to the data sheet it has two comparators.
The above links will explain why
CMCON=7
is needed.

[xobx]

Ok, thanks.

But it still dosent work as I want it :/

@   device  pic16F648A, hs_osc, wdt_off, mclr_on, lvp_off, protect_off
DEFINE OSC 20

LED1 var PORTB.1
PRESS var PORTA.1
CMCON=7


loop:

If press=1 then       
            high led1  
            else
            low led1  
            endif      
            goto loop   
            end

When i transfer it LED1 starts to shine directly even if PortA.1 doesnt have +5V

:/

[mackrackit]

Maybe the LED is backwards

Do you have PORTA.1 tied to ground with a resistor (10K) so it is not floating?

[xobx]

Floating ?

[xobx]

Should it be like this?

[mackrackit]

Yes, that is correct.

[xobx]

I added it and it worked!

Thanks.

[xobx]

If I make the code like tis:

@   device  pic16F648A, hs_osc, wdt_off, mclr_on, lvp_off, protect_off
DEFINE OSC 20

LED1 var PORTB.1
PRESS var PORTA.1
CMCON=7


loop:

If press=0 then       
            high led1  
            else
            low led1  
            endif      
            goto loop   
            end

Should it be like this?

[mackrackit]

If I make the code like tis:

@   device  pic16F648A, hs_osc, wdt_off, mclr_on, lvp_off, protect_off
DEFINE OSC 20

LED1 var PORTB.1
PRESS var PORTA.1
CMCON=7


loop:

If press=0 then       
            high led1  
            else
            low led1  
            endif      
            goto loop   
            end

Should it be like this?

No. The first way is what you want. When the switch is open the pin is "0"LOW. When the switch is closed the pin is "1"HIGH.

If you are using push buttons, you will need to use either a normally open "NO" or a normally closed "NC".

The resistor keeps the pin LOW (no float). High resistance is used to minimize the current through the switch (just a little short).

Depending on how you look at it this is called a pull up or a pull down.