Knob.ino

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/*
 Controlling a servo position using a potentiometer (variable resistor)
 by Michal Rinott <http://people.interaction-ivrea.it/m.rinott>

 modified on 8 Nov 2013
 by Scott Fitzgerald

 modified for the ESP32 on March 2017
 by John Bennett
 
 see  http://www.arduino.cc/en/Tutorial/Knob for a description of the original code

 * Different servos require different pulse widths to vary servo angle, but the range is 
 * an approximately 500-2500 microsecond pulse every 20ms (50Hz). In general, hobbyist servos
 * sweep 180 degrees, so the lowest number in the published range for a particular servo
 * represents an angle of 0 degrees, the middle of the range represents 90 degrees, and the top
 * of the range represents 180 degrees. So for example, if the range is 1000us to 2000us,
 * 1000us would equal an angle of 0, 1500us would equal 90 degrees, and 2000us would equal 1800
 * degrees.
 * 
 * Circuit: (using an ESP32 Thing from Sparkfun)
 * Servo motors have three wires: power, ground, and signal. The power wire is typically red,
 * the ground wire is typically black or brown, and the signal wire is typically yellow,
 * orange or white. Since the ESP32 can supply limited current at only 3.3V, and servos draw
 * considerable power, we will connect servo power to the VBat pin of the ESP32 (located
 * near the USB connector). THIS IS ONLY APPROPRIATE FOR SMALL SERVOS. 
 * 
 * We could also connect servo power to a separate external
 * power source (as long as we connect all of the grounds (ESP32, servo, and external power).
 * In this example, we just connect ESP32 ground to servo ground. The servo signal pins
 * connect to any available GPIO pins on the ESP32 (in this example, we use pin 18.
 * 
 * In this example, we assume a Tower Pro SG90 small servo connected to VBat.
 * The published min and max for this servo are 500 and 2400, respectively.
 * These values actually drive the servos a little past 0 and 180, so
 * if you are particular, adjust the min and max values to match your needs.
 */

// Include the ESP32 Arduino Servo Library instead of the original Arduino Servo Library
#include <ESP32Servo.h> 

Servo myservo;  // create servo object to control a servo

// Possible PWM GPIO pins on the ESP32: 0(used by on-board button),2,4,5(used by on-board LED),12-19,21-23,25-27,32-33 
int servoPin = 18;      // GPIO pin used to connect the servo control (digital out)
// Possible ADC pins on the ESP32: 0,2,4,12-15,32-39; 34-39 are recommended for analog input
int potPin = 34;        // GPIO pin used to connect the potentiometer (analog in)
int ADC_Max = 4096;     // This is the default ADC max value on the ESP32 (12 bit ADC width);
                        // this width can be set (in low-level oode) from 9-12 bits, for a
                        // a range of max values of 512-4096
  
int val;    // variable to read the value from the analog pin

void setup()
{
    // Allow allocation of all timers
    ESP32PWM::allocateTimer(0);
    ESP32PWM::allocateTimer(1);
    ESP32PWM::allocateTimer(2);
    ESP32PWM::allocateTimer(3);
  myservo.setPeriodHertz(50);// Standard 50hz servo
  myservo.attach(servoPin, 500, 2400);   // attaches the servo on pin 18 to the servo object
                                         // using SG90 servo min/max of 500us and 2400us
                                         // for MG995 large servo, use 1000us and 2000us,
                                         // which are the defaults, so this line could be
                                         // "myservo.attach(servoPin);"
}

void loop() {
  val = analogRead(potPin);            // read the value of the potentiometer (value between 0 and 1023)
  val = map(val, 0, ADC_Max, 0, 180);     // scale it to use it with the servo (value between 0 and 180)
  myservo.write(val);                  // set the servo position according to the scaled value
  delay(200);                          // wait for the servo to get there
}