Analog Feedback Servos

by Bill Earl

published August 24, 2013, last edited January 22, 2025
last major update March 05, 2023

posted in Adafruit Products

Beginner

Skill guide

Servos as Input Devices

Another neat feature of feedback servos is that they can be used as an input device too! The Servo Record/Play Demo lets you record a series of servo movements, then it will replay them back for you! The recorded positions are saved in EEPROM, so they will be remembered even after resetting or powering down the Arduino

To run this demo, first wire up your Servo as in the Fritzing diagram below:

Components used:

Arduino Uno
Feedback Servo
2x pushbuttons
LED (most any 3 or 5mm led will work)
220 ohm resistor
Misc. jumpers
Breadboard

Next, download the example sketch from Github using this button:

Download File

Copy Code

// SPDX-FileCopyrightText: 2018 Limor Fried for Adafruit Industries
//
// SPDX-License-Identifier: MIT

// Example code for recording and playing back servo motion with a 
// analog feedback servo
// http://www.adafruit.com/products/1404


#include <Servo.h>
#include <EEPROM.h>

#define CALIB_MAX 512
#define CALIB_MIN 100
#define SAMPLE_DELAY 25 // in ms, 50ms seems good

uint8_t recordButtonPin = 12;
uint8_t playButtonPin = 7;
uint8_t servoPin = 9;
uint8_t feedbackPin = A0;
uint8_t ledPin = 13;

Servo myServo;  
  
void setup() {
  Serial.begin(9600);
  pinMode(recordButtonPin, INPUT);
  digitalWrite(recordButtonPin, HIGH);
  pinMode(playButtonPin, INPUT);
  digitalWrite(playButtonPin, HIGH);
  pinMode(ledPin, OUTPUT);
  
  Serial.println("Servo RecordPlay");
}

void loop() {
 if (! digitalRead(recordButtonPin)) {
   delay(10);
   // wait for released
   while (! digitalRead(recordButtonPin));
   delay(20);
   // OK released!
   recordServo(servoPin, feedbackPin, recordButtonPin);
 }
 
  if (! digitalRead(playButtonPin)) {
   delay(10);
   // wait for released
   while (! digitalRead(playButtonPin));
   delay(20);
   // OK released!
   playServo(servoPin, playButtonPin);
 }
}

void playServo(uint8_t servoPin, uint8_t buttonPin) {
  uint16_t addr = 0;
  Serial.println("Playing");


  myServo.attach(servoPin);
  while (digitalRead(buttonPin)) {    
    uint8_t x = EEPROM.read(addr);
    Serial.print("Read EE: "); Serial.print(x);
    if (x == 255) break;
    // map to 0-180 degrees
    x = map(x, 0, 254, 0, 180);
    Serial.print(" -> "); Serial.println(x);
    myServo.write(x);
    delay(SAMPLE_DELAY);
    addr++;
    if (addr == 512) break;
  }
  Serial.println("Done");
  myServo.detach();
  delay(250);  
}

void recordServo(uint8_t servoPin, uint8_t analogPin, uint8_t buttonPin) {
  uint16_t addr = 0;
  
  Serial.println("Recording");
  digitalWrite(ledPin, HIGH);
  


  
  pinMode(analogPin, INPUT); 
  while (digitalRead(buttonPin)) {
     uint16_t a = analogRead(analogPin);
     
     Serial.print("Read analog: "); Serial.print(a);
     if (a < CALIB_MIN) a = CALIB_MIN;
     if (a > CALIB_MAX) a = CALIB_MAX;
     a = map(a, CALIB_MIN, CALIB_MAX, 0, 254);
     Serial.print(" -> "); Serial.println(a);
     EEPROM.write(addr, a);
     addr++;
     if (addr == 512) break;
     delay(SAMPLE_DELAY);
  }
  if (addr != 512) EEPROM.write(addr, 255);

  digitalWrite(ledPin, LOW);

  Serial.println("Done");
  delay(250);
}

// SPDX-FileCopyrightText: 2018 Limor Fried for Adafruit Industries
//
// SPDX-License-Identifier: MIT

// Example code for recording and playing back servo motion with a 
// analog feedback servo
// http://www.adafruit.com/products/1404


#include <Servo.h>
#include <EEPROM.h>

#define CALIB_MAX 512
#define CALIB_MIN 100
#define SAMPLE_DELAY 25 // in ms, 50ms seems good

uint8_t recordButtonPin = 12;
uint8_t playButtonPin = 7;
uint8_t servoPin = 9;
uint8_t feedbackPin = A0;
uint8_t ledPin = 13;

Servo myServo;  
  
void setup() {
  Serial.begin(9600);
  pinMode(recordButtonPin, INPUT);
  digitalWrite(recordButtonPin, HIGH);
  pinMode(playButtonPin, INPUT);
  digitalWrite(playButtonPin, HIGH);
  pinMode(ledPin, OUTPUT);
  
  Serial.println("Servo RecordPlay");
}

void loop() {
 if (! digitalRead(recordButtonPin)) {
   delay(10);
   // wait for released
   while (! digitalRead(recordButtonPin));
   delay(20);
   // OK released!
   recordServo(servoPin, feedbackPin, recordButtonPin);
 }
 
  if (! digitalRead(playButtonPin)) {
   delay(10);
   // wait for released
   while (! digitalRead(playButtonPin));
   delay(20);
   // OK released!
   playServo(servoPin, playButtonPin);
 }
}

void playServo(uint8_t servoPin, uint8_t buttonPin) {
  uint16_t addr = 0;
  Serial.println("Playing");


  myServo.attach(servoPin);
  while (digitalRead(buttonPin)) {    
    uint8_t x = EEPROM.read(addr);
    Serial.print("Read EE: "); Serial.print(x);
    if (x == 255) break;
    // map to 0-180 degrees
    x = map(x, 0, 254, 0, 180);
    Serial.print(" -> "); Serial.println(x);
    myServo.write(x);
    delay(SAMPLE_DELAY);
    addr++;
    if (addr == 512) break;
  }
  Serial.println("Done");
  myServo.detach();
  delay(250);  
}

void recordServo(uint8_t servoPin, uint8_t analogPin, uint8_t buttonPin) {
  uint16_t addr = 0;
  
  Serial.println("Recording");
  digitalWrite(ledPin, HIGH);
  


  
  pinMode(analogPin, INPUT); 
  while (digitalRead(buttonPin)) {
     uint16_t a = analogRead(analogPin);
     
     Serial.print("Read analog: "); Serial.print(a);
     if (a < CALIB_MIN) a = CALIB_MIN;
     if (a > CALIB_MAX) a = CALIB_MAX;
     a = map(a, CALIB_MIN, CALIB_MAX, 0, 254);
     Serial.print(" -> "); Serial.println(a);
     EEPROM.write(addr, a);
     addr++;
     if (addr == 512) break;
     delay(SAMPLE_DELAY);
  }
  if (addr != 512) EEPROM.write(addr, 255);

  digitalWrite(ledPin, LOW);

  Serial.println("Done");
  delay(250);
}