Hello all.

I am trying to implement several remote keypads with one central master,
very similar to a home security system.  Each keypad uses a 4x4 matrix
keypad, a 16x2 backlit LCD, 3 diodes, a piezo buzzer, and 2-wire serial
communications with the master.

I have been gradually incorporating each of these into a PIC16C84, but a
rapidly running out of I/O (only 13) pins even with the use of shift
registers and a software SPI.  I eventually want to migrate this to a
cheaper chip, perhaps an 18-pin PIC16C5x or PIC16C62.

My question is:  despite their relatively low prices, the addition of the
shift registers dramatically increases the real estate and wiring.  Should
I consider the PIC16C63A with its larger size but increased I/O capability?
Then I could utilize the USART for communications and the built-in SPI.  I
think the additional cost of PIC16C63A would almost be offset by the
additional cost of the shift registers for the PIC16C5x, let alone the
reduced software complexity using the built-in USART and SPI.  Of course I
will not utilize many of the features of the PIC16C63A - but that does
leave room for possible expansion.

Any comments or suggestions?


Regards,

--John