70 lines
3.7 KiB
C++
70 lines
3.7 KiB
C++
/*
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Controlling a servo position using a potentiometer (variable resistor)
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by Michal Rinott <http://people.interaction-ivrea.it/m.rinott>
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modified on 8 Nov 2013
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by Scott Fitzgerald
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modified for the ESP32 on March 2017
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by John Bennett
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see http://www.arduino.cc/en/Tutorial/Knob for a description of the original code
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* Different servos require different pulse widths to vary servo angle, but the range is
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* an approximately 500-2500 microsecond pulse every 20ms (50Hz). In general, hobbyist servos
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* sweep 180 degrees, so the lowest number in the published range for a particular servo
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* represents an angle of 0 degrees, the middle of the range represents 90 degrees, and the top
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* of the range represents 180 degrees. So for example, if the range is 1000us to 2000us,
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* 1000us would equal an angle of 0, 1500us would equal 90 degrees, and 2000us would equal 1800
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* degrees.
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*
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* Circuit: (using an ESP32 Thing from Sparkfun)
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* Servo motors have three wires: power, ground, and signal. The power wire is typically red,
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* the ground wire is typically black or brown, and the signal wire is typically yellow,
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* orange or white. Since the ESP32 can supply limited current at only 3.3V, and servos draw
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* considerable power, we will connect servo power to the VBat pin of the ESP32 (located
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* near the USB connector). THIS IS ONLY APPROPRIATE FOR SMALL SERVOS.
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*
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* We could also connect servo power to a separate external
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* power source (as long as we connect all of the grounds (ESP32, servo, and external power).
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* In this example, we just connect ESP32 ground to servo ground. The servo signal pins
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* connect to any available GPIO pins on the ESP32 (in this example, we use pin 18.
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*
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* In this example, we assume a Tower Pro SG90 small servo connected to VBat.
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* The published min and max for this servo are 500 and 2400, respectively.
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* These values actually drive the servos a little past 0 and 180, so
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* if you are particular, adjust the min and max values to match your needs.
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*/
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// Include the ESP32 Arduino Servo Library instead of the original Arduino Servo Library
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#include <ESP32Servo.h>
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Servo myservo; // create servo object to control a servo
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// 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
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int servoPin = 18; // GPIO pin used to connect the servo control (digital out)
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// Possible ADC pins on the ESP32: 0,2,4,12-15,32-39; 34-39 are recommended for analog input
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int potPin = 34; // GPIO pin used to connect the potentiometer (analog in)
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int ADC_Max = 4096; // This is the default ADC max value on the ESP32 (12 bit ADC width);
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// this width can be set (in low-level oode) from 9-12 bits, for a
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// a range of max values of 512-4096
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int val; // variable to read the value from the analog pin
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void setup()
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{
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myservo.attach(servoPin, 500, 2400); // attaches the servo on pin 18 to the servo object
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// using SG90 servo min/max of 500us and 2400us
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// for MG995 large servo, use 1000us and 2000us,
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// which are the defaults, so this line could be
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// "myservo.attach(servoPin);"
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}
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void loop() {
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val = analogRead(potPin); // read the value of the potentiometer (value between 0 and 1023)
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val = map(val, 0, ADC_Max, 0, 180); // scale it to use it with the servo (value between 0 and 180)
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myservo.write(val); // set the servo position according to the scaled value
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delay(200); // wait for the servo to get there
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}
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