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Generic keypad scan driver



///////////////////////////////////////////////////////////////////////////
//// KBD.C ////
//// Generic keypad scan driver ////
//// ////
//// kbd_init() Must be called before any other function. ////
//// ////
//// c = kbd_getc(c) Will return a key value if pressed or /0 if not ////
//// This function should be called frequently so as ////
//// not to miss a key press. ////
//// ////
//// (C) Copyright 1996,1997 Custom Computer Services ////
//// ////
///////////////////////////////////////////////////////////////////////////

////////////////// The following defines the keypad layout on port B
#byte kbd = 6 // Keypad is connected to port B (address 6)

//Keypad connection: (for example column 0 is B2)
// Bx:


#ifdef blue_keypad ///////////////////////////////////// For the blue keypad
#define COL0 (1 << 2)
#define COL1 (1 << 3)
#define COL2 (1 << 6)

#define ROW0 (1 << 4)
#define ROW1 (1 << 7)
#define ROW2 (1 << 1)
#define ROW3 (1 << 5)

#else ////////////////////////////////////////////////// For my keypad
#define COL0 (1 << 6)
#define COL1 (1 << 2)
#define COL2 (1 << 3)

#define ROW0 (1 << 4)
#define ROW1 (1 << 5)
#define ROW2 (1 << 1)
#define ROW3 (1 << 7)

#endif

#define ALL_ROWS (ROW0|ROW1|ROW2|ROW3)
#define ALL_PINS (ALL_ROWS|COL0|COL1|COL2)

// Keypad layout:
char const KEYS[4][3] = {{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'*','0','#'}};

#define KBD_DEBOUNCE_FACTOR 33 // Set this number to apx n/333 where
// n is the number of times you expect
// to call kbd_getc each second



void kbd_init() {
#ifdef __PCM__
port_b_pullups(true); // If not PCM be sure to use external pullups
#endif
}


char kbd_getc( ) {
static byte kbd_call_count;
static short int kbd_down;
static char last_key;
static byte col;

byte kchar;
byte row;

kchar='\0';
if(++kbd_call_count>KBD_DEBOUNCE_FACTOR) {
switch (col) {
case 0 : set_tris_b(ALL_PINS&~COL0);
kbd=~COL0&ALL_PINS;
break;
case 1 : set_tris_b(ALL_PINS&~COL1);
kbd=~COL1&ALL_PINS;
break;
case 2 : set_tris_b(ALL_PINS&~COL2);
kbd=~COL2&ALL_PINS;
break;
}

if(kbd_down) {
if((kbd & (ALL_ROWS))==(ALL_ROWS)) {
kbd_down=false;
kchar=last_key;
last_key='\0';
}
} else {
if((kbd & (ALL_ROWS))!=(ALL_ROWS)) {
if((kbd & ROW0)==0)
row=0;
else if((kbd & ROW1)==0)
row=1;
else if((kbd & ROW2)==0)
row=2;
else if((kbd & ROW3)==0)
row=3;
last_key =KEYS[row][col];
kbd_down = true;
} else {
++col;
if(col==3)
col=0;
}
}
kbd_call_count=0;
}
set_tris_b(ALL_PINS);
return(kchar);
}

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