The JY-LKM1638 is a simple 3 wire I/O device that can be added to any Micro Controller project.  The JY-LKM1638 uses a proprietary serialized interface to allow for the use of 8 seven segment displays, 8 LEDs, and 8 push button switches. 

The Data Sheet for the module can be download Here.
The module can be ordered from Here.

Here is a link to the MBED Library that I wrote and published for this device

Here I have interfaced the I/O device to the 8051. 

This library has been specifically writted for th Atmel at89c51cc03 processor using the Keil C complier and IDE, but the functions have been written in such a way that they should be easily portable to other C or C++ platforms.  Link

Have Fun!!