6502.org

Code: Select all

 #define bitmask(bitnbr) (1 << (bitnbr))

 const char keymap[] = { '0','1','2','3',   // row 0, columns 0..3
                         '4','5','6','7',   // row 1, columns 0..3
                         '8','9','A','B',   // row 2, columns 0..3
                         'C','D','E','F',   // row 3, columns 0..3
                          0 };              // null (no switch pressed)

/********************************************
 *  Scan Keypad                             *
 ********************************************/

 char scan(void)                            // scan keypad matrix
 { char keyndx = 16;                        // null (no switch pressed)
   for(char col = 0; col < 4; col++)        // column 0..3
   { DDRD = bitmask(col);                   // set 'col' bit to output, all others inputs
     PORTD = ~(bitmask(col));               // set 'col' bit to '0', pull-up all other pins
     for(char row = 0; row < 4; row++)      // rows 0..3
     { if(PIND & bitmask(row + 4) == 0)     // if active low key press (row bit == '0')
         keyndx = row * 4 + col;            // save index, 0..15
     }                                      // next row
   }                                        // next col
   return(keymap[keyndx]);                  // return 0 or ASCII keycode
 }

Code: Select all

	// 0=input, 1=output
	
	// rows (PD pins 4-7), columns PD, pins 0-3)
	DDRD = 0b11110000;			// port D, set to 4-7 (output), 0-3 (input)
	PORTD = 0xff;				// port D, pins 4-7 output 1111, pull ups enabled for pins 0-3
	
	// VIA pins (lower nibble=PC, pins 3 to 0 (reversed), upper nibble=PB6 (bit4), PB2 (bit5), PB1 (bit6), PB0 (bit7)  
	DDRC = 0xff;				// port C, set to output
	PORTC = 0x0;				// port C, pull ups disabled
	DDRB = 0xff;				// port B, set to output
	PORTB = 0;					// port B, pull ups disabled

Code: Select all

unsigned char scanKbd(void)
{
	// ensure that 
	//PORTD = 0xff;
	unsigned char scanresult;
	
	scanresult = 0;

	for (int row=4;row<=7;row++)
	{
		KYBD_bit_set(DDRD, KYBD_bit(row));					// set row as output 
		KYBD_bit_clear(PORTD, KYBD_bit(row));
		for (int col=0;col<=3;col++)
		{
			if (KYBD_bit_get(PIND, KYBD_bit(col))==0)
			{
				KYBD_bit_set(scanresult, KYBD_bit(col));
				KYBD_bit_set(scanresult, KYBD_bit(row));
			}
		}
		KYBD_bit_set(PORTD, KYBD_bit(row));
		KYBD_bit_clear(DDRD, KYBD_bit(row));					// set row as input (disable it)
	}
	return(scanresult);
}