#define KeyEn porta.6
#define KeyEnTris trisa.6
#define KeyTris trisb

#define KeyDelay 30
#define KeyRepeat 10

#define key_none    0
#define key_back    1
#define key_up      2
#define key_dw      3
#define key_enter   4

unsigned char keys=0,previous,edges,KeyCount;

char ReadKeyPad(){
char i;
    previous=keys;              //keep copy of previous state
    option_reg.7=0;             //WPUs on
    KeyTris|=0x3c;              //B2-B6 input
    KeyEnTris=0;                //A6 output
    KeyEn=0;                    //and low
    delay_us(10);               //see text below
    keys=(portb>>2)&0x0f;       //read keys
    keys^=0x0f;                 //invert them so 1=pressed
    KeyEnTris=1;                //switch en back to input
    KeyTris&=0xc3;              //switch b2-b6 back to output
    if(keys==0)                 //if no key pressed
        return(0);              //return zero

    //now do key repeat and delay stuff
    //keys xor previous gives us a 1 if a key has changed
    //ANDing this value with the new keys pressed gives
    //keys that were 0 last time and 1 now = new presses

    if(((keys^previous)&keys)==0){  //if no new presses
                                //must be repeating key
        if(--KeyCount!=0)       //decrement key count and
            return(0);          //return zero as time not up
        KeyCount=KeyRepeat;     //reset key timer
    }else{
                                //must be new key press
        KeyCount=KeyDelay;      //set initial delay  
        edges=((keys^previous)&keys);//see above
    }
    i=0;
    while((edges&(1<<i))==0){   //change bit pattern into 1 to 3
        i++;
    }
    return (++i);               //and return it
}