> Van: Athanasios Gogos <athanasios.gogos@NCL.AC.UK>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: HELPIC
> Datum: dinsdag 9 februari 1999 2:48
>
> Hello,

Hello Athanasios,

> I want to interface on a master PIC a 4-digit LCD display and
> a 4x4 keypad and this node to communicate with two slave
> nodes(interfaced only with a 4 digit LCD) with a two wire I2C bus.
> The problem I came up with is By using the PIC16C5X family do not hane
> enough I/O lines to do that, and also I want to keep the external
hardware
>  to a minimum.
> Any sugestions on to which PIC should I use and if I have to use
> external circuitry how that can be done?
> Thank you in advance

Use the LCD-module in 4-bit mode (using 4 data & 3 control) connected to
PortB.  Double-use the 4 outputs to the LCD-Module as outputs to your 4x4
Keypad. Use PortA.0 to 3 as inputs from your KeyPad (Pull-up's required).
Use PortA.4 as I2C Output (don't forget the Pull-up resistor !) and the
non-used line on port B as I2C Clock.

Greetz,
  Rudy Wieser

P.s.
Take care that the 4x4 KeyPad does not short-circuit the PIC-outputs when
multiple buttons are pressed ... (use Diodes in series with buttons or
driving lines)