Microcontorller Tutorial

Microcontorller Tutorial#

Ben Manning, Purdue University

Last Modified: 2025-12-04

Overview#

In this lab, you will reverse-engineer and replicate key components of a basic appliance using an Arduino Nano. The goal is to explore common functionalities like sensor inputs, data display, and motor control, which are often found in consumer appliances. Each task includes wiring diagrams, sample code, and exercises to apply your knowledge. This hands-on approach simulates real-world reverse engineering, where you must modify existing systems and overcome limitations.

Learning Objectives#

Interface with GPIO to control inputs and outputs.
Implement digital and analog sensors to simulate user input.
Display information using I2C displays.
Communicate with multiple devices using I2C and UART protocols.
Control DC brushed motors and servos using PWM.
Understand the limitations of the Arduino Nano in reverse-engineering contexts.

Materials Needed#

Arduino Nano
Breadboard and jumper wires
Resistors (\(10k\Omega\), \(220\Omega\))
Push button
Potentiometer
7-segment display
I2C LCD display (16x2)
DC motor (brushed)
L298N motor driver module
Servo motor
Ultrasonic sensor (HC-SR04)
Power supply (5V)

Disclosure#

This lab is designed in the assumption that the learner has a general knowledge set of electronics and programming. The learner does not need to know the formatting needed for an Arduino or C specifically, but should be familiar with how functions are designed in programming.

Schematics are not generally provided in this document. While there is a wiring guide to state what pins are used where, the user is assumed to know generally how standard devices are attached in a circuit. For example, a potentiometer will need to have an input voltage and common ground attached to outside pins for it to operate as a voltage divider.

Introduction to Arduino#

Arduino is an open-source electronics platform that simplifies the process of building and controlling electronics. The Arduino Nano, used in this lab, is a small, versatile board that includes digital and analog pins, PWM outputs, and communication protocols like I2C and UART. It is widely used in prototyping and reverse-engineering tasks due to its low cost and simplicity.

General information on an Arduino and using the Arduino IDE#

If you do not have the Arduino IDE already, please download and install the environment. The Arduino IDE can be downloaded at not cost from Arduino LLC at https://www.arduino.cc/software.

Functionally, an Arduino has two primary functions that must be inside of every program that is uploaded to it. The setup() function runs once and is used to initialize different parts of the microcontroller. After the setup() function, the loop() function runs essentially as a loop initialized with while(0==0), meaning that the program will run indefinitely until it is halted by turning the device off, or it runs into an error that causes it to crash.

Inside of the Arduino IDE, there are a variety of examples and libraries that come pre-installed to assist you with your project at hand. https://www.arduino.cc also has a community tab with a forum and project hub that can likely assist with whatever issues you may have.

Advanced Microcontroller systems (AVRs)#

The main processor for the Arduino an Atmel ATMEGA328 chip which is in the AVR family of microprocessors. You can use the processor independently using more traditional programming similar to what you will experience in ECE362 at Purdue. This opens up the processor to a variety of other functions and applications that are partially limited on an Arduino due to Arduino LLC’s mission to make the microcontroller more user-friendly. There is also a lot of documentation available on programming AVRs if you wish to go down this road.

Reverse engineering plays a large role in electronics competition as a way to spin off a competitor’s product. Using an inexpensive microcrontroller can often allow for a competitor to cut costs by limiting the amount of analog electronics needed to make a system by simulating the analog nature of some devices. Recreating the device using a microcontroller can also assist you with understanding the process that a device goes through to complete a task.

Your primary task for this lab is to create a functional replica of the thermostat that was reverse engineered in the beginning of the course using an Arduino Nano along with assorted sensors and switches. Document your processes and findings in your journal like you would any other lab.

Below you will find a variety exercises that will introduce you to different functions of the Arduino Nano and assist you with some sample code to get moving on the primary task at hand. Use the exercises as you see fit to complete your task, and then as a resource in the future as you replicate other products.

GPIO and Digital Sensors/Buttons#

Objective#

Interface with basic digital sensors to simulate appliance control, such as buttons and indicators.

Wiring Diagram#

Connect a push button to digital pin D2 and an LED to pin D13. Pull the button LOW with a 10K\(\Omega\) resistor. Use a 220\(\Omega\) resistor in series with the LED. Ensure that there is proper voltage and ground attached to all components.

Sample Code#

const int buttonPin = 2;
const int ledPin = 13;
int buttonState = 0;

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  buttonState = digitalRead(buttonPin);
  if (buttonState == HIGH) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
}

Exercise#

Modify the code so that the LED toggles on and off with each button press, staying on after one press and turning off after another.

Analog Sensors for Control#

Objective#

Use an analog sensor to simulate variable control, such as temperature adjustment or speed control.

Wiring Diagram#

Connect the center pin of a potentiometer to pin A0 and an LED to pin D9. Use a 220\(\Omega\) resistor in series with the LED. Make sure the outside pins of the potentiometer are attached to 5V and GND of the Arduino.

Sample Code#

const int potPin = A0;
const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int sensorValue = analogRead(potPin);
  int outputValue = map(sensorValue, 0, 1023, 0, 255);
  analogWrite(ledPin, outputValue);
}

Exercise#

Modify the code to control the frequency of a buzzer using the potentiometer instead of controlling an LED.

7-Segment Display#

Objective#

Display numeric data, such as temperature or time, on a 7-segment display. Ensure that there is proper voltage and ground attached to all components.

Wiring Diagram#

Connect the 7-segment display to pins D2 through D8 using 220\(\Omega\) resistors.

Sample Code#

const int segments[] = {2, 3, 4, 5, 6, 7, 8};

const byte digitPatterns[10] = {
  B00111111, B00000110, B01011011, B01001111, B01100110,
  B01101101, B01111101, B00000111, B01111111, B01101111
};

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(segments[i], OUTPUT);
  }
}

void loop() {
  displayDigit(3);  // Display number 3
  delay(1000);
}

void displayDigit(int digit) {
  byte pattern = digitPatterns[digit];
  for (int i = 0; i < 7; i++) {
    digitalWrite(segments[i], bitRead(pattern, i));
  }
}

Exercise#

Modify the code to cycle through digits 0 to 9 on the 7-segment display every second.

I2C LCD Display#

Objective#

Display information on an I2C LCD (16x2).

Wiring Diagram#

Connect the I2C LCD to the Arduino Nano’s SDA (pin A4) and SCL (pin A5). Ensure that there is proper voltage and ground attached to all components.

Sample Code#

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);  // LCD address 0x27

void setup() {
  lcd.begin();
  lcd.backlight();
  lcd.print("Hello, World!");
}

void loop() {}

Exercise#

Modify the code to display “Appliance ON” when a button is pressed and “Appliance OFF” when the button is released.

DC Motor Control Using PWM#

Objective#

Control the speed and direction of a DC motor using PWM signals.

Wiring Diagram#

Connect the motor to an L298N motor driver, and use pins D9, D10, and D11 for control. Ensure that there is proper voltage and ground attached to all components.

Sample Code#

const int in1Pin = 9;
const int in2Pin = 10;
const int enablePin = 11;

void setup() {
  pinMode(in1Pin, OUTPUT);
  pinMode(in2Pin, OUTPUT);
  pinMode(enablePin, OUTPUT);
}

void loop() {
  digitalWrite(in1Pin, HIGH);
  digitalWrite(in2Pin, LOW);
  analogWrite(enablePin, 128);  // Set motor speed
  delay(2000);

  analogWrite(enablePin, 0);  // Stop motor
  delay(1000);
}

Exercise#

Modify the code so that the motor speed is controlled by a potentiometer connected to pin A0.

Servo Control Using PWM#

Objective#

Control a servo motor to move parts, like dials or levers, in an appliance.

Wiring Diagram#

Connect the servo motor’s signal wire to pin D9. Ensure that there is proper voltage and ground attached to all components.

Sample Code#

#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(9);
}

void loop() {
  myServo.write(0);  // Rotate servo to 0 degrees
  delay(1000);
  myServo.write(90);  // Rotate to 90 degrees
  delay(1000);
}

Exercise#

Modify the code to control the servo position using a potentiometer connected to pin A0.

Advanced Exercise#

Modify the code to control the servo WITHOUT the servo library.

Limitations of the Arduino Nano in Reverse Engineering#

Memory: The Nano’s 2KB SRAM may limit the complexity of the operations or number of libraries you can run simultaneously.
Processing Power: The 16 MHz clock speed may not suffice for real-time data processing or handling multiple sensor inputs concurrently.
Pin Count: The limited number of I/O pins (14 digital) restricts how many devices you can connect simultaneously.
No Native Wireless Communication: Wireless communication, such as Bluetooth or Wi-Fi, is not built-in and requires external modules.

Another Disclosure: Use other Microcontrollers in the future!#

As you may be aware, there are a wide variety of other microcontollers out there that vary in size, functionality, and usability. Explore your options to better fit your applications. Below are some of the major micorcontrollers that are commercially available quite regularly.

Arduino (AVRs, Arudino Uno, Nano, Micro, Mega …)
Pros:
- Open-source
- Simple to use
- Wide variety of models and styles
- Large hobby community
Cons:
- Limited in functionality unless used as AVR
- Argued to be outdated compared to newer microcontrollers
ESP (ESP32, ESP8266)
Pros:
- Open-source
- A lot of embedded functionality such as Wi-Fi and Bluetooth
- Large hobby community
Cons:
- Main board is more difficult to solder than other controllers
- Limited anlaog pins- need to use an external mux to get more functionality
STM (STM8, STM32)
Pros:
- Used a lot in commercial products
- Very large functionality
Cons:
- Proprietary
- Need licence to program properly
Raspberry Pi Pico (RP2040)
Pros:
- New
- Inexpensive
- Developing user base
- New versions being released with a lot of different functionality
- Ideally, this page will also have Pico tutorials too.
Cons:
- Proprietary
- New
Raspberry Pi (mini-computer)
While not a microcontroller, a Raspberry Pi can be programmed with much of the same functions as the above microcrontollers with a lot more memory and power.
Pros:
- Inexpensive
- strong user base
- Full Linux OS support
- WiFi, HDMI, USB, Ethernet, Camera input ready to go.
Cons:
- Proprietary
- Needs OS installed
- Takes longer to setup, but can streamline in the future.

Microcontorller Tutorial

Contents

Microcontorller Tutorial#

Overview#

Learning Objectives#

Materials Needed#

Disclosure#

Introduction to Arduino#

General information on an Arduino and using the Arduino IDE#

Advanced Microcontroller systems (AVRs)#

GPIO and Digital Sensors/Buttons#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

Analog Sensors for Control#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

7-Segment Display#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

I2C LCD Display#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

DC Motor Control Using PWM#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

Servo Control Using PWM#

Objective#

Wiring Diagram#

Sample Code#

Exercise#

Advanced Exercise#

Limitations of the Arduino Nano in Reverse Engineering#

Another Disclosure: Use other Microcontrollers in the future!#