Output Devices Using ESP32-C3: Servo, OLED, and Buzzer Control

Objective

The goal of this project is to demonstrate the use of multiple output devices — a SG90 servo motor, an SSD1306 OLED display, and a buzzer — using the Seeed Studio XIAO ESP32-C3 microcontroller. This setup showcases how mechanical movement, visual feedback, and audio indication can be combined to create an interactive embedded system.

Components Used

1. ESP32-C3 XIAO

• Ultra-compact microcontroller based on ESP32-C3 chip
  
• Supports Wi-Fi and Bluetooth
  
• Operates on 3.3V logic
  
• Small form factor with USB-C, perfect for wearable and IoT projects
  

2. SG90 Servo Motor

• Micro servo motor used for small mechanical actuation
  
• Controlled using PWM signal
  
• Operates on 5V power
  
• Rotation range: 0° to 180°, typically used for angles like 0°, 90°, 180°
  

3. SSD1306 OLED Display (128x64)

• Monochrome graphical display
  
• Uses I2C communication
  
• Address: 0x3C
  
• Used to display text status of servo position
  

4. Buzzer

• Active buzzer that beeps when given a HIGH signal
  
• Used to provide audio feedback when the servo changes position
  

5. Other Tools

• Breadboard
  
• Jumper wires
  
• External 5V power supply (for servo)
  
• USB-C cable (for programming ESP32-C3 XIAO)
  

Circuit Diagram

Important: The servo must be powered externally, not from the 3.3V ESP32 pin. Ensure GND is common between ESP and the power source.

How It Works

• The servo rotates between 0° and 90° every second.
  
• The OLED shows the current servo position text, centered on screen.
  
• A buzzer beeps each time the servo changes position.
  

Code

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <ESP32Servo.h>

// OLED display setup

#define SCREEN_WIDTH 128

#define SCREEN_HEIGHT 64

#define OLED_RESET -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Pin Definitions

#define BUZZ D7

#define SERVO_PIN D3

Servo myServo;

void setup() {

  Serial.begin(115200);

  pinMode(BUZZ, OUTPUT);

  digitalWrite(BUZZ, LOW);

  // Attach servo

  myServo.attach(SERVO_PIN);

  myServo.write(0); // Start at 0 degrees

  // OLED setup

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

    Serial.println("OLED init failed");

    while (true);

  }

  display.clearDisplay();

  display.setTextSize(2);

  display.setTextColor(SSD1306_WHITE);

  centerText("Servo + Buzzer", 0);

}

void loop() {

  // Move to 0°

  myServo.write(0);

  buzzBeep();

  updateDisplay("0 deg");

  delay(1000);

  // Move to 90°

  myServo.write(90);

  buzzBeep();

  updateDisplay("90 deg");

  delay(1000);

}

// Play a beep

void buzzBeep() {

  digitalWrite(BUZZ, HIGH);

  delay(150);

  digitalWrite(BUZZ, LOW);

}

// Update the display text

void updateDisplay(const char* text) {

  display.fillRect(0, 30, SCREEN_WIDTH, 20, BLACK); // Clear area

  centerText(text, 30);

}

// Center text function

void centerText(const char* text, int y) {

  int16_t x1, y1;

  uint16_t w, h;

  display.getTextBounds(text, 0, y, &x1, &y1, &w, &h);

  int x = (SCREEN_WIDTH - w) / 2;

  display.setCursor(x, y);

  display.print(text);

  display.display();

}



Code Explanation

Servo myServo;

Uses the ESP32Servo library to control a PWM signal for the SG90.

display.getTextBounds()

Calculates the width/height of the text to allow horizontal centering.

buzzBeep()

Turn the buzzer on and off for a short time to create a beep sound.

updateDisplay()

Clears a specific portion of the OLED and writes updated text.

Demo

This code has been implemented and successfully tested on the XIAO ESP32-C3 board, images08 were taken on both the 0° and 90° turn of the servo, with indication of buzzer. The Working video is also given in this link.

Challenges and Learnings

• Power Management: The servo motor can draw more current than the ESP32-C3 can safely supply. It’s essential to use an external 5V power source and share GND.
  
• Timing Sync: Managing the display update and servo movement with delays works, but in more complex cases you might want to use non-blocking timers.
  
• OLED Centering: Centering text on the OLED requires pixel math, but using getTextBounds() simplifies it.
  

Conclusion

This project helped in understanding how to:

• Use PWM to control servos
  
• Display dynamic content on an OLED using I2C
  
• Integrate a buzzer for simple sound feedback
  
• Coordinate multiple output devices through simple logic and timing
  

Possible Extensions

• Use button input to change servo angle interactively.
  
• Add sensor input (e.g., light or motion sensor) to trigger servo movement.
  
• Connect it to Wi-Fi or Bluetooth to control remotely via a phone app or web page.