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playing with key on PIC16F877A

 
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ccslearner



Joined: 12 Jan 2013
Posts: 10

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playing with key on PIC16F877A
PostPosted: Wed Apr 03, 2013 10:40 pm     Reply with quote
hello everyone,

I am beginner in embedded system programming, still i have been learning it. The below code is when switch is pressed --> led ON.
My question is can I modify it to get when switch is pressed --> led OFF, such as reverse of this code, and initially all the led's are ON ?
Code:

#include <trial_1.h>
#define KEY_1 0x10
#define LED_1 0x01
#define KEY_2 0x20
#define LED_2 0x02
#define KEY_3 0x40
#define LED_3 0x04
#define SET_PIN 0x70
#define LED_OFF 0x0

#use delay(crystal=4000000)

void main ()
{
int8 key_input = LED_OFF;
port_b_pullups (true);
set_tris_b (SET_PIN) ; // 0111 0000 -> configure RB0, RB1, RB2 as output
                       //           -> configure RB4, RB5, RB6 as input
output_b (LED_OFF) ;   // Initialize all to off
 

//infinite loop
while (1)
  {
   key_input = SET_PIN & ~input_b();
     
   if ( key_input==KEY_1)        //  0x10  0001 0000 configure RB4 as input RB4
      output_b (LED_1) ; // 0x01  0000 0001 configure Rb0 as output
   else if( key_input==KEY_2 )   // 0x20 0010 0000 configure RB5 as input RB5
      output_b (LED_2) ;   //0x02  0000 0010 configure RB1 as output
   else if( key_input==KEY_3)   // 0x40 0100 0000 configure RB6 as input  RB6
      output_b (LED_3) ; //0x04  0000 0100 configure RB2 as output
   }
}
 

Thanks
ezflyr



Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA

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PostPosted: Thu Apr 04, 2013 6:52 am     Reply with quote
Hi,

I'd recommend that you use the 'Input' function to test your switch, and the 'Output_toggle' function to control your LED. You should be able to accomplish what you want in 5 or 6 lines of code, and it will be much simpler and easy to read!


Code:


#define SW_Input PIN_A0
#define LED PIN_A1

main()
{

Output_high(LED);

while(1)
{

if (input(SW_Input))
output_toggle(LED);

}



Obviously, change the pin defines to match your hardware, and change the 'Output_high' statement to 'Output_low' to reverse the startup behaviour of the LED. You'll also need to add the #include for your PIC, and the correct fuses.

John (the kinder and gentler version!)
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