> Hello Adam,
>
> > The routine can be found in this C file:
> > 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
> http://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();
>  }
> }
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> David Harris wrote...
>
> >CHALLENGE: can you scan a keyboard, and run an LCD display with only 8 pins/bits
> >= 1 port -- without extra active hardware?
>
> How about operating a keypad with nothing more than a single PIC A/D
> input pin?
>
> The diagram below shows how this can be done, by connecting the
> row/column lines of the keypad to resistors so that each key (the X's in
> the diagram below) results in a different resistance value.  This
> resistance is connected, along with a load resistor (the 22K shown
> below), in a voltage divider between Vcc and ground; each key gives a
> different voltage, thus a different A/D reading.
>
> I didn't dream this up on my own, BTW, so I can't take "challenge"
> credit for it; I saw it about a year ago in the Design Ideas column in
> one of the electronics rags (either EDN or Electronic Design, I forget
> which).  It should work, even if it is a little unusual...
>
>      X-------X-------X-------X----------+--Vcc
>      |       |       |       |          |
>      |       |       |       |          |
>      X-------X-------X-------X---4.7K---+
>      |       |       |       |          |
>      |       |       |       |          |
>      X-------X-------X-------X---10K----+
>      |       |       |       |          |
>      |       |       |       |          |
>      X-------X-------X-------X---15K----+
>      |       |       |       |
>      |     1.2K    2.4K    3.6K
>      |       |       |       |
>      +-------+-------+-------+--> To PIC A/D Input
>                              |
>                             22K
>                              |
>                             GND
>
> Hope this helps...
>
> Dave
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

>Hi-
>Hey this is great!  Can you push multiple keys?  That should be possible, but we
>would need a 16 bit A/D.
>David H
>
>Dave Dilatush wrote:
>
>>David Harris wrote...
>>
>>>CHALLENGE: can you scan a keyboard, and run an LCD display with only 8 pins/bits
>>>= 1 port -- without extra active hardware?
>>>
>>How about operating a keypad with nothing more than a single PIC A/D
>>input pin?
>>
>>The diagram below shows how this can be done, by connecting the
>>row/column lines of the keypad to resistors so that each key (the X's in
>>the diagram below) results in a different resistance value.  This
>>resistance is connected, along with a load resistor (the 22K shown
>>below), in a voltage divider between Vcc and ground; each key gives a
>>different voltage, thus a different A/D reading.
>>
>>I didn't dream this up on my own, BTW, so I can't take "challenge"
>>credit for it; I saw it about a year ago in the Design Ideas column in
>>one of the electronics rags (either EDN or Electronic Design, I forget
>>which).  It should work, even if it is a little unusual...
>>
>>     X-------X-------X-------X----------+--Vcc
>>     |       |       |       |          |
>>     |       |       |       |          |
>>     X-------X-------X-------X---4.7K---+
>>     |       |       |       |          |
>>     |       |       |       |          |
>>     X-------X-------X-------X---10K----+
>>     |       |       |       |          |
>>     |       |       |       |          |
>>     X-------X-------X-------X---15K----+
>>     |       |       |       |
>>     |     1.2K    2.4K    3.6K
>>     |       |       |       |
>>     +-------+-------+-------+--> To PIC A/D Input
>>                             |
>>                            22K
>>                             |
>>                            GND
>>
>>Hope this helps...
>>
>>Dave
>>
>>--
>>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
>>email EraseMElistservmitvma.mit.edu with SET PICList DIGEST in the body
>>
>
>--
>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
>email RemoveMElistservEraseMEEraseMEmitvma.mit.edu with SET PICList DIGEST in the body
>
>
>
>
>

> Hello Wouter,
>
> > - you have a pin 'left over' (or two, when you don't read). Use them all
> to
> > drive E in and-fashion (you can use a D-R and gate, I think that does not
> > count as active?)
>
>     This gave me an idea, just wait... I need to elaborate it:
>
>     Well, here we go. Sorry for attaching a 33KB bitmap on this email, but
> it's small. :)
>
>     When you're scanning the keyboard, RB3:RB0 are outputs and RB7:RB4 are
> inputs. You'll need the external pull-downs (about 10K). As we'll see below,
> the internal pull-ups wouldn't work.
>
>     Just do the keyboard scanning as usual positive-logic. When you have a
> key pressed, the corresponding input pin will go high when you put the
> corresponding output pin high.
>
>     As you can see, the LCD will ignore these signals, because you need to
> have RB1 AND RB2 HIGH for it to see a HIGH on the enable line.
>
>     I think R1-R8 can be 1K and R9 10K. The diodes can be 1N4148. This will
> make the LCD-ENA line LOW when RB1 OR RB2 are LOW. This is the normal
> keyboard scanning situation, where you turn RB0=HI, read ROW1 on RB7:RB4,
> turn RB0=LO RB1=HI, read ROW2 on RB7:RB4 and so on. You never will have both
> RB1 and RB2 HIGH when scanning the keyboard.
>
>     You can use negative logic for the keys if you invert the LCD-ENA signal
> with a transistor, but then it's not a only passive circuit anymore.
>
>     Have I won the award? So I want divide the price with Wouter. ;^)
>
>     Best regards,
>
>     Brusque
>
> -----------------------------------
> Edson Brusque
> Research and Development
> C.I.Tronics Lighting Designers Ltda
> Blumenau  -  SC  -  Brazil
> http://www.citronics.com.br
> Say NO to HTML mail
> -----------------------------------
>
>   ------------------------------------------------------------------------
>                 Name: keyb2.bmp
>    keyb2.bmp    Type: Pbrush File (image/bmp)
>             Encoding: base64

>Edson Brusque wrote...
>
> >    Let's say no keys are pressed. You've charged all the caps with current
> >passing through the diodes, then you havn't discharged any caps because no
> >key are pressed when you turned RD4 LOW. Then you have RD7:RD4 as inputs
> >reading LOW, because no current passes from the cap to the port by the keys.
> >No current also passes through the (now reversed) diodes.
> >
> >    How can this work?
>
>It doesn't.
>
>Darn it, I had pullup resistors on the port pins in this design when I
>went to bed last night.  But when I got up this morning I couldn't
>remember what the heck I'd put them in there for.  So I took them out.
>
>Now I know why they were there in the first place.
>
>Attached is the corrected design, with pullups included.
>
>Dave

> I might be blind but I don't see the big problem. The high nibble drives the
> control lines, and (via D+R) the key rows. The low nibble drives the LCD
> data pins and reads the key columns (use pull up or down R's). The only
> snatch is that to scan one row you'll have to toggle E, which can cause an
> operation on the LCD. To get around this problem:
>
> - make sure the operation is a no-op, like reading, or writing to a location
> that does not matter (maybe one of the user-defined characters)
> - reverse the operation immediately afterwards (for instance erase the char
> just written)
> - you have a pin 'left over' (or two, when you don't read). Use them all to
> drive E in and-fashion (you can use a D-R and gate, I think that does not
> count as active?)
>
> It is a pity I have no time to try this (one-hand typing with a baby in the
> other arm is difficult enough).
>
> Wouter van Ooijen
>
> Van Ooijen Technische Informatica: http://www.voti.nl
> Jal compiler for PIC uC's:  http://www.voti.nl/jal
> PICs kopen? http://www.voti.nl/shop
>
> --
> http://www.piclist.com hint: To leave the PICList
> TakeThisOuTpiclist-unsubscribe-requestKILLspamspammitvma.mit.edu