PFC8574 4x4 keypad: correct wiring?
Ok look at this image:


I'm not sure how your keypad is layed out but if you use a probe pin to test your connections via a multimeter, you can mark which ones correspond to the image.

I am ASSUMING you are going to use the code from arduino playground.

This is the format:

Pins of keypad (IN THE IMAGE) - Pins of PFC8547

Here are the pin connections:

1 - nothing

2 - 9

3 - 4

4 - 6

5 - 7

6 - 10

7 - 11

8 - 5

Also include the pull-up resistors.
Your ABCD keys will be ignored

(This is like wiring a bomb...)