Above is a simple I/O interface using an AVR microcontroller. The i/o pins are controlled by the AVR and can be used to drive LEDs, control RC servos, etc.
Using the attached relay circuit it can also be used to control relays.
The schematics also provides a programming interface.
Partlist
1 x ATTiny 2313
1 x MAX 232
1 x MAX 232
Thanks