AVR based parking system - Simple Arduino Based Automated Parking Lot System - page 32

Main board
In the main board, a ATmega16 AVR microcontroller is used to control the program. A
16x1 multiplexer is used for the16 signals that come from parking slots. So just five pins of
microcontroller (four pins are to control multiplexer and one is for multiplexer output) are
used, instead of 16 pins. The microcontroller selects a signal among the 16 signals by four
multiplexer control pins and then reads it from the multiplexer output. Also, two shift re-
gisters are used to have a lot of serially output for microcontroller just using three pins of
microcontroller. The needed pushbutton and a LCD to display useful information are con-
sidered in this board. You can see the PCB layout of this board ( Figure 1.13 ) with Altium
Designer ® , which is a registered trademark of Altiume Company . In addition, you can
see its source file in attendant CD.