AVR based parking system - Simple Arduino Based Automated Parking Lot System - page 21

write_outputs() function
The all microcontroller outputs are sent serially by two shift registers. The following
items are considered for microcontroller outputs.
1. Turn a motor to lift the exit arm gate down.
2. Turn a motor to lift the exit arm gate up.
3. Turn a motor to lift the entrance arm gate down
4. Turn a motor to lift the entrance arm gate up
5. Green LED
6. Red LED
7. First 7segment
8. Second 7segment.