PIC - is there a value for RB7?

Question

I read the port RB7, and in the if a check the value. if there is output on RB7 I want that the led on my chip light up (led D1), but it burns all the time even when there is nothing connected to RB7. What i'm doing wrong? That's the PIC 18F4550 It's written in mplab v8.63 and the C18 compiler.

void main (void) 
{  
 TRISD = 0x00;            // PORTD  als uitgang 
 TRISB = 0b00110000;      // RB4 en RB5 als ingang 

 RCONbits.IPEN = 0;    // prioriteit uit 
 INTCONbits.GIE = 1;   // enable interrupt 
 INTCONbits.RBIE = 1;  // interrupt portB aan 

 TRISBbits.TRISB7 = 0; 
 TRISBbits.TRISB6 = 0; 
 TRISBbits.TRISB3 = 0; 

 while(1) 
 {  
  _asm sleep _endasm  
 } 
} 
#pragma interrupt ISR 
void ISR (void) 
{ 
 if (INTCONbits.RBIF==1) 
 {   
  if(LATBbits.LATB7 == 1)    // value on RB7 ? 
  { 
   LATDbits.LATD1 ^= 1;    // D2 togglen 
  } 
 }  
 INTCONbits.RBIF = 0; 
}

Sorry! that's the pic 18F4550, and with the c18 compiler. thanks for helping! — user001

nobody nobody · Accepted Answer · 2011-03-19T15:56:11

Three things:

The inputs are always high or low regardless of whether you have anything wired up to them. Do you have appropriate pull-up or pull-down circuitry?
You probably need to debounce that input to keep a single input from triggering multiple state changes.
It doesn't look like you ever set output D1 on startup. I wouldn't assume that it defaults to any particular state.

PIC - is there a value for RB7?

2 Answers