expanding port using a SPI or I2C based IC

arun · Guest

Hi,

How can I expand the number of input ports using an I that uses I2C or SPI based communication, at present I am using 74151 multiplexer .

I require around 25 input ports.

cheers
arun

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

If you are asking about an I2C IO device, check out something like a Phillips PCA9554, PCA9555, PCA9556, PCA9557

Tom-H-PIC · Joined: 08 Sep 2003 Posts: 105 Location: New Castle, DE

Look at Microchips MCP23016
also TI makes a chip like this also.

dyeatman · Joined: 06 Sep 2003 Posts: 1912 Location: Norman, OK

Here is some good info from Peter Anderson on an I2C port expander:

http://www.phanderson.com/printer/8574/8574.html

Here is another that includes CCS compatible code:

http://www.phanderson.com/PIC/PICC/CCS_PCM/8574_1.html