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turn high 2-3 port at the same time

 
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takumi



Joined: 07 Mar 2009
Posts: 14

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turn high 2-3 port at the same time
PostPosted: Wed Aug 04, 2010 12:37 am     Reply with quote
Code:

#define SW1 PIN_B0
#define SW2 PIN_C5
#define BUZZER PIN_D6
#define LED1 PIN_D7
#define LED2 PIN_E2
                           
void main(){
       
   while(1){   
      if(!input(SW1) && input(SW2)) output_high(LED1);
                                                     
      else if (input(SW1) && !input(SW2)) output_high(LED2);
                             
      else if(!input(SW1) & !input(SW2)){
       output_d(0b11000000);                   
       output_high(LED2);                                 
         }                       
                                       
      else {                       
         output_low(LED1); 
         output_low(LED2);           
         output_low(BUZZER);
         }
   }
                     
}

Hi all, is there any method to turn on both LED1 & Buzzer at the same time?

I have tried to use:
Code:

{
output_high(LED1); 
output_high(LED2);           
output_high(BUZZER);
}

But the simulation in Proteus shows the LED1 & BUZZER just blinking.
But if I used the code as below, both turn high:
Code:

{
output_d(0b11000000);
}

Why does this thing happen? Any idea? Please help.
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Wed Aug 04, 2010 1:54 am     Reply with quote
Search for previous threads about RMW (read-modify-write) issue.

In a short, it happens because you are overloading the pins, so that the output high level is below specified minimum input high value.
takumi



Joined: 07 Mar 2009
Posts: 14

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PostPosted: Wed Aug 04, 2010 6:11 am     Reply with quote
tq.. found the solution already. Just add 330 resistor before the LED.
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