I am bogged down in this project
I am bogged down in this project
Bill,
I have a document that I produced that shows the connections from a 4 * 4 matrix keypad to the 8574 and the basic code to use it. I do not lay claim to the originally of the code as it is what I pulled together from other peoples work on the web. There are two versions of the 8574, the 'A' version has a different address range. Therefore if you really wanted you could add 8 off 8574's and 8 off 8574A's to give a total of 16 * 8 128 extra I/O on 2 wires from the Arduino!
There are variants of the keypads and there appears to be no standard for the pin outs. However it is not difficult to determine what the connections are with a multimeter. The code can then be easily changed to produce the output you want.
I could probably convert the notes I have to a PDF if you wish and sent it via email. I do not know how to add documents to my replies on this site. Actually I have never tried!
Bob
Bob;
Could you email me you notes on this project.
Do you have a library for the 8574 and a working example.
Thanks Averil
Try this, full description for using this chip with the keypad
Try this, full description for using this chip with the keypad