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arduino-cli/libraries/ESP32Servo/examples/Knob/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 <ESP32_Servo.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()
+{
+  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
+}
+