Hi-

I was hoping that I could do both a 4x4 kb and an LCD with only one register.
However, I do not think it is possible - although I wouldn't put it past some of
the people on this list comig up with a solution.  You need 4 outputs to scan
the kb, and 4 inputs to read the kb.  The LCD needs 4 bits data, a register
select bit, and a control bit.  As I see it, you start messing up the display if
you try to multiple use the pins.  Best I can do is  one port and one extra
line, so...

CHALLENGE: can you scna a keyboard, and run an LCD display with only 8 pins/bits
= 1 port -- without extra active hardware?

David H

Edson Brusque wrote:

> Hello Adam,
>
> > The routine can be found in this C file:
> > http://www.ubasics.com/adam/electronics/ha/ver000101/node.c
> > search for "char scankp(void)"
>
>     what I'm doing seens to be simpler. The routine on the bottom of this
> email uses a 4x4 keypad in PORTB. ROWS are on RB3:RB0 and columns on
> RB7:RB4. RB3:RB0 (outputs) is also the DB7:DB4 lines to the LCD. The code is
> below and although it's a bit BIG in C, it could be made smaller in
> Assembly.
>
>     Best regards,
>
>     Brusque
>
> -----------------------------------
> Edson Brusque
> Research and Development
> C.I.Tronics Lighting Designers Ltda
> Blumenau  -  SC  -  Brazil
> www.citronics.com.br
> Say NO to HTML mail
> -----------------------------------
>
> /* **************************************** */
> /* Sorry, no coments :)                     */
> uns8 get_key_pressed(void)
> {
>  uns8 key_buffer;
>
>  key_buffer = 0;
>
>  PORTB = 0b1110;
>  delay_cycles(5);
>  if (!PORTB.B4) key_buffer = '1';
>  if (!PORTB.B5) key_buffer = '2';
>  if (!PORTB.B6) key_buffer = '3';
>  if (!PORTB.B7) key_buffer = '4';
>
>  PORTB = 0b1101;
>  delay_cycles(5);
>  if (!PORTB.B4) key_buffer = '5';
>  if (!PORTB.B5) key_buffer = '6';
>  if (!PORTB.B6) key_buffer = '7';
>  if (!PORTB.B7) key_buffer = '8';
>
>  PORTB = 0b1011;
>  delay_cycles(5);
>  if (!PORTB.B4) key_buffer = '9';
>  if (!PORTB.B5) key_buffer = '0';
>  if (!PORTB.B6) key_buffer = 'A';
>  if (!PORTB.B7) key_buffer = 'B';
>
>  PORTB = 0b0111;
>  delay_cycles(5);
>  if (!PORTB.B4) key_buffer = 'C';
>  if (!PORTB.B5) key_buffer = 'D';
>  if (!PORTB.B6) key_buffer = 'U';
>  if (!PORTB.B7) key_buffer = 'E';
>
>  return key_buffer;
> }
>
> /* **************************************** */
> /* This is a debounce sugestion, never used */
> uns8 get_key_pressed_debounce(void)
> {
>  if (get_key_pressed()) {
>     delay_ms(50);
>     return get_key_pressed();
>  }
> }
>
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