Servo Motor Control for ESP32 (Arduino Framework)

Generate complete servo motor control code for ESP32 using the Arduino framework.

Quick Start

When user requests servo control, generate code that:

•Uses ESP32Servo library (not standard Servo.h)
•Selects appropriate PWM-capable pin
•Configures LEDC peripheral correctly
•Implements requested behavior (sweep, position, interactive)

Platform Requirements

Refer to esp32 platform skill for:

•Complete GPIO specifications
•Hardware constraints and strapping pins
•Power requirements (3.3V logic)
•ADC, DAC, and communication interface details

Key constraints for servo (from ESP32 platform):

•✅ All GPIO pins support PWM via LEDC peripheral
•❌ Avoid input-only pins (34, 35, 36, 39) - cannot be used as outputs
•❌ Avoid strapping pins if possible (0, 2, 5, 12, 15) - affect boot mode
•⚠️ Operating voltage: 3.3V logic (not 5V tolerant)
•⚠️ Max current per GPIO: 40 mA (recommended 20 mA)

Arduino Framework Basics

Program Structure

cpp

void setup() {
  // Runs once at startup
  // Initialize pins, Serial, servo, etc.
}

void loop() {
  // Runs repeatedly after setup()
  // Main program logic
}

Serial Communication

cpp

Serial.begin(115200);         // Initialize Serial (typical ESP32 baud rate)
Serial.println("Hello");      // Print with newline
Serial.print(value);          // Print without newline

Timing Functions

cpp

delay(1000);                  // Delay 1000ms (blocking)
delayMicroseconds(100);       // Delay 100μs (blocking)
unsigned long ms = millis();  // Milliseconds since boot
unsigned long us = micros();  // Microseconds since boot

ESP32-Specific: LEDC PWM

Critical for servo: ESP32 uses LEDC (LED Control) peripheral, not traditional PWM timers.

LEDC Features

•16 independent channels (0-15)
•Frequency range: 1 Hz to 40 MHz
•Resolution: 1-16 bits (configurable)
•Any GPIO pin can be assigned to any channel

Why This Matters for Servo

The ESP32Servo library abstracts LEDC complexity, but understanding the underlying mechanism helps:

•Servo signals require precise 50Hz PWM
•Pulse width controls servo position (typically 500-2400μs)
•LEDC automatically manages the timing

You don't need to configure LEDC manually - the ESP32Servo library handles it!

Pin Selection

Recommended Servo Pins

Best choices: 16, 17, 18, 19, 21, 22, 23, 25, 26, 27 Avoid:

•0, 2, 5, 12, 15 (strapping pins - affect boot)
•34, 35, 36, 39 (input-only pins)
•6-11 (connected to flash memory)
•1, 3 (UART0 - USB serial)

Default Pin

If user doesn't specify: Use GPIO 18

Code Generation

Basic Servo Sweep Example

cpp

#include <ESP32Servo.h>

Servo myServo;

// Pin configuration
const int servoPin = 18;  // PWM-capable pin

void setup() {
  Serial.begin(115200);

  // ESP32Servo specific configuration
  myServo.setPeriodHertz(50);           // Standard 50Hz servo
  myServo.attach(servoPin, 500, 2400);  // Attach with pulse width range

  // Move to center position
  myServo.write(90);
  delay(500);

  Serial.println("Servo initialized");
}

void loop() {
  // Sweep from 0 to 180 degrees
  Serial.println("Sweeping 0 -> 180");
  for (int pos = 0; pos <= 180; pos++) {
    myServo.write(pos);
    delay(15);  // 15ms delay for smooth movement
  }

  delay(500);

  // Sweep from 180 to 0 degrees
  Serial.println("Sweeping 180 -> 0");
  for (int pos = 180; pos >= 0; pos--) {
    myServo.write(pos);
    delay(15);
  }

  delay(500);
}

Fixed Position Example

cpp

#include <ESP32Servo.h>

Servo myServo;
const int servoPin = 18;

void setup() {
  Serial.begin(115200);

  myServo.setPeriodHertz(50);
  myServo.attach(servoPin, 500, 2400);

  // Set to specific position (0-180 degrees)
  myServo.write(90);  // Center position

  Serial.println("Servo at 90 degrees");
}

void loop() {
  // Servo holds position
  // No need to continuously write
}

Interactive Control (Serial Input)

cpp

#include <ESP32Servo.h>

Servo myServo;
const int servoPin = 18;

void setup() {
  Serial.begin(115200);

  myServo.setPeriodHertz(50);
  myServo.attach(servoPin, 500, 2400);
  myServo.write(90);

  Serial.println("Servo Control Ready");
  Serial.println("Enter angle (0-180):");
}

void loop() {
  if (Serial.available() > 0) {
    int angle = Serial.parseInt();

    // Validate range
    if (angle >= 0 && angle <= 180) {
      myServo.write(angle);
      Serial.print("Servo moved to: ");
      Serial.println(angle);
    } else {
      Serial.println("Invalid angle. Enter 0-180.");
    }

    // Clear remaining input
    while (Serial.available() > 0) {
      Serial.read();
    }
  }
}

Multiple Servos

cpp

#include <ESP32Servo.h>

Servo servo1;
Servo servo2;

const int servo1Pin = 18;
const int servo2Pin = 19;

void setup() {
  Serial.begin(115200);

  // Initialize servos on different LEDC channels (automatic)
  servo1.setPeriodHertz(50);
  servo1.attach(servo1Pin, 500, 2400);

  servo2.setPeriodHertz(50);
  servo2.attach(servo2Pin, 500, 2400);

  // Different positions
  servo1.write(45);
  servo2.write(135);

  Serial.println("Multiple servos initialized");
}

void loop() {
  // Synchronized movement
  for (int pos = 0; pos <= 180; pos++) {
    servo1.write(pos);
    servo2.write(180 - pos);  // Mirror movement
    delay(15);
  }
  delay(1000);
}

Important ESP32Servo Library Details

Library Installation

code

// Arduino IDE: Tools > Manage Libraries > Search "ESP32Servo"
// PlatformIO: lib_deps = ESP32Servo

Key Differences from Standard Servo Library

•

Must call setPeriodHertz() before attach()

cpp

myServo.setPeriodHertz(50);  // 50Hz for standard servos

•

Attach with pulse width range

cpp

myServo.attach(pin, minUs, maxUs);
// minUs: min pulse width (default 544, standard 500-1000)
// maxUs: max pulse width (default 2400, standard 2000-2400)

•
Uses LEDC channels automatically
- •ESP32Servo manages LEDC channels internally
- •Supports up to 16 servos (16 LEDC channels)

Typical Servo Pulse Widths

Servo Type	Min (0°)	Max (180°)
Standard	1000μs	2000μs
Extended	500μs	2400μs
Continuous	1000μs	2000μs

Recommended: Use attach(pin, 500, 2400) for maximum range

Continuous Rotation Servos

cpp

myServo.setPeriodHertz(50);
myServo.attach(servoPin, 1000, 2000);

// Continuous servos use position as speed
myServo.write(90);   // Stop
myServo.write(0);    // Full speed one direction
myServo.write(180);  // Full speed other direction

Wiring

Standard Servo Wiring

code

Servo Motor    ESP32
-----------    -----
Signal (Orange/Yellow) → GPIO [PIN] (e.g., 18)
VCC (Red)      → 5V (external power recommended)
GND (Brown/Black) → GND

Power Considerations

⚠️ Important Power Notes:

•
Small servos (SG90, 9g micro): Can power from ESP32 5V pin if:
- •Only 1-2 servos
- •Not under heavy load
- •ESP32 powered via USB (500mA available)
•
Standard servos (SG5010, MG996R): MUST use external power
- •Draw 100-500mA under load
- •Can damage ESP32 if powered from board
- •Use external 5V power supply (1-2A)
- •Connect grounds together (ESP32 GND to external PSU GND)

•

Proper external power setup:

code

External 5V PSU
├─ VCC → Servo VCC (Red)
└─ GND → Servo GND (Brown) AND ESP32 GND (common ground)

ESP32
└─ GPIO 18 → Servo Signal (Orange)

Code Patterns

Smooth Acceleration

cpp

void moveServoSmooth(Servo &servo, int targetPos, int currentPos) {
  int step = (targetPos > currentPos) ? 1 : -1;

  for (int pos = currentPos; pos != targetPos; pos += step) {
    servo.write(pos);
    delay(10);  // Adjust for speed
  }
}

// Usage
int currentPosition = 90;
moveServoSmooth(myServo, 180, currentPosition);
currentPosition = 180;

Non-blocking Movement

cpp

int targetPosition = 90;
int currentPosition = 90;
unsigned long lastMoveTime = 0;
const int moveInterval = 15;  // ms between steps

void loop() {
  unsigned long currentTime = millis();

  if (currentTime - lastMoveTime >= moveInterval) {
    if (currentPosition < targetPosition) {
      currentPosition++;
      myServo.write(currentPosition);
    } else if (currentPosition > targetPosition) {
      currentPosition--;
      myServo.write(currentPosition);
    }
    lastMoveTime = currentTime;
  }

  // Other code runs without blocking
}

Detach to Save Power

cpp

void setup() {
  myServo.attach(servoPin);
  myServo.write(90);
  delay(500);  // Wait for servo to reach position
  myServo.detach();  // Saves power, servo stops holding position
}

Required Libraries

cpp

#include <ESP32Servo.h>  // ESP32-specific servo library

Installation:

•Arduino IDE: Library Manager → "ESP32Servo" by Kevin Harrington
•
PlatformIO: Add to platformio.ini:
ini
```
lib_deps = ESP32Servo
```

Troubleshooting

Servo Jitters or Doesn't Move Smoothly

•Ensure stable power supply (use external 5V for standard servos)
•Check for loose wiring
•Add 100-470μF capacitor across servo power and ground
•Ensure common ground between ESP32 and external power

Servo Position Inaccurate

•Calibrate pulse width: Try different values in attach(pin, min, max)
•Standard servos: attach(pin, 1000, 2000)
•Extended range: attach(pin, 500, 2400)

Multiple Servos Interfere

•ESP32Servo automatically manages LEDC channels
•Ensure each servo uses different GPIO pin
•Use external power for multiple servos

Servo Draws Too Much Current

•Never power multiple servos from ESP32 5V pin
•Use external 5V power supply (1-2A minimum)
•Connect ESP32 GND to external PSU GND (common ground required)

Additional Resources

See resources/templates/ for more examples.