EIE373 Microcontroller Systems and Interface Laboratory Exercise 2: AVR Timer/Counter ProgrammingR

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EIE373 Microcontroller Systems and Interface

Laboratory Exercise 2: AVR Timer/Counter Programming

(Deadline: Check the course information)

Objective:

1. To develop C programs with timers under the Arduino platform.

2. To develop a C program with a counter under the Arduino platform.

Introduction:

This experiment introduces the use of timers and a counter inside the AVR microcontroller. Students MUST use the AVR timers in the delay function to finish this lab. Using simple loops only without timers to count the delay or built-in functions is not acceptable.

Equipment:

Atmel Studio

The Arduino Starter Kit

Procedure:

Section A: Write a C Program to toggle an LED by using a timer

1. Write a C program to toggle an LED connected to PB0 (you should connect the LED to PB0 with a resistor) every second. Use the timer with Normal mode to generate a one- second time delay. Note that the clock frequency of the Arduino Start Kit is 16 MHz.

2. Repeat Step 1, but the timer is in CTC mode this time.

DO NOT skip Section A and goto Section B directly. You must finish the laboratory exercise step by step; otherwise, you will find that it is not easy to follow.

Section B: Write a C Program to simulate the traffic lights

1. Write a C program to simulate the traffic lights using different pins. You should use a timer in Normal mode. Note that the Arduino Start Kit's clock frequency is 16 MHz.

A set of traffic lights for cars (Light 3): PB0, PB1, PB2 (3 LEDs) A set of traffic lights for cars (Light 2): PB3, PB4, PB5 (3 LEDs) A set of traffic lights for pedestrians (Light 1): PC4, PC5 (2 LEDs)

Implement the following pattern:

Current state	Light 1	Light 2	Light 3	Time duration	Next state
1	Red	Green	Red	5 seconds	2
2	Red	Yellow	Red	1 second	3
3	Red	Red	Red	1 second EIE373 Microcontroller Systems and Interface Laboratory Exercise 2: AVR Timer/Counter ProgrammingR	4
4	Red	Red	Red + Yellow	1 second	5
5	Green	Red	Green	5 seconds	6
6	Green Blinking	Red	Yellow	1 second	7
7	Red	Red	Red	1 second	8
8	Red	Red + Yellow	Red	1 second	1

2. Repeat Step 1, but the timer is in CTC mode this time.

Section C: Write a C program to count a switch

Connect a switch to pin T0 (PD4, Counter 0) or T1 (PD5, Counter 1) and a LED to PC0. There are two states in the switch: State 0 and 1. When it is in State 0, the LED is off. When it is in State 1, the LED is on. At the beginning, the switch is in State 0. When the switch is pressed three times and in State 0, it goes to State 1. When the switch is pressed three times and in State 1, it goes to State 0. You should use counter programming in CTC mode to implement this application.

You may find that sometimes the state may change, but you do not press the switch three times. It is because of the bouncing effect of the switch. Please google “bouncing switch” to understand the bouncing effect and “debouncing switch” to find a solution to reduce the bouncing effect.

Demonstrate Sections B and C to our student helpers.