-----Original Message-----
From: Russell McMahon <apptech@clear.net.nz>
To: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
Date: Monday, 26 June 2000 23:32
Subject: Re: Re: Relay question...


>>As an alternative I have also used the I2C bus to control output devices
(8
>>outputs) PCF8574 if I remember correctly.  Each of the devices has 4
>>addresses allowing 32 outputs from 2 control wires, in addition there is
an
>>"A" part that allows an addition 4 addresses giving the possibility of 64
>>outputs from  the 2 wire bus.
>
>


Could also use eg 4094 or similar 8 bit serial load / parallel output shift
registers  chained together as required but these often have low ish drive
and MAY need buffers as well. eg ULN2803 etc. Advantage is only 3 lines to
control the whole array (clock, data, load). Care needs be taken with ripple
carry for large arrays.




RM