SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 - Joystick - Servo Motor

In this tutorial, we are going to learn how to use ESP32 and a joystick to control two servo motors or a pan-tilt kit with servos.

A joystick has two built-in potentiometers square with each other (called X-axis and Y-axis). These potentiometers output the analog values (called X-value and Y-value) on VRX and VRY pins. We will use these analog values to control two servo motors independently: X-value controls servo #1 and Y-value controls servo #2. In the case of the pan-tilt kit, the movement of two servo motors creates 3-D movement.

There are two application use cases:

Use case 1: The servo motors rotate according to the movement of the joystick's thump:

The angles of servo motors are in proportion to the values of the joystick's X-value and Y-value.
When we release the joystick's thump ⇒ all values returns back to the center values ⇒ servo motors automatically returns back to the center position

Use case 2: use the joystick to command servo motors (up/down/left/right commands)

When joystick's thump is pushed to the left, move the servo motor #1 in a clockwise direction step-by-step
When joystick's thump is pushed to the right, move the servo motor #1 in an anti-clockwise direction step-by-step
When joystick's thump is pushed up, move the servo motor #2 in clockwise direction step-by-step
When joystick's thump is pushed down, move the servo motor #2 in an anti-clockwise direction step-by-step
When we release the joystick's thump ⇒ the servo motors will not return to the center position
If the joystick is pressed (push button), The servo motors will return to the center position

We will explore the code for both use cases in the next parts.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Joystick
2	×	Servo Motor
2	×	(Optional) Pan-tilt kit with servo motor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32
1	×	(Recommended) Power Splitter For ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links in this section are Amazon affiliate links, meaning we may earn a commission at no additional cost to you if you make a purchase through them. Additionally, some links direct you to products from our own brand, DIYables.

Introduction to Joystick and Servo Motor

If you do not know about joystick and servo motor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

How to connect ESP32 with joystick and servo motor using breadboard

This image is created using Fritzing. Click to enlarge image

How to connect ESP32 with joystick and servo motor using screw terminal block breakout board

How to connect ESP32 with joystick and servo motor

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code

ESP32 Code - The servo motors rotate according to the movement of the joystick's thump

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Connect the joystick and servo motor to the ESP32 board as above the wiring diagram.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Type ServoESP32 on the search box, then look for the servo library by Jaroslav Paral. Please be aware that both version 1.1.1 and 1.1.0 are affected by bugs. Kindly choose a different version.
Click Install button to install servo motor library for ESP32.

Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP32

Open Serial Monitor
Push the joystick in some direction
See the servo motor's rotation
See the result on Serial Monitor

COM6

Send

Coming soon

Autoscroll Show timestamp

Clear output

9600 baud

Newline

You may have noticed that the servo motor does not move proportionally to the joystick movement. This issue is not due to the joystick or the servo motor itself, but rather the ADC of the ESP32. The end of this tutorial will explain why this happens.

ESP32 Code - Use the joystick to command servo motors

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-joystick-servo-motor */ #include <Servo.h> #include <ezButton.h> #define VRX_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to VRX pin #define VRY_PIN 39 // ESP32 pin GPIO39 (ADC0) connected to VRY pin #define SW_PIN 23 // ESP32 pin GPIO23 connected to SW pin #define SERVO_X_PIN 13 // ESP32 pin GPIO13 connected to Servo motor 1 #define SERVO_Y_PIN 25 // ESP32 pin GPIO25 connected to Servo motor 2 #define COMMAND_NO 0x00 #define COMMAND_LEFT 0x01 #define COMMAND_RIGHT 0x02 #define COMMAND_UP 0x04 #define COMMAND_DOWN 0x08 #define LEFT_THRESHOLD 1000 #define RIGHT_THRESHOLD 3000 #define UP_THRESHOLD 1000 #define DOWN_THRESHOLD 3000 #define UPDATE_INTERVAL 100 // 100ms ezButton button(SW_PIN); Servo xServo; // create servo object to control a servo 1 Servo yServo; // create servo object to control a servo 2 int valueX = 0 ; // to store the X-axis value int valueY = 0 ; // to store the Y-axis value int xAngle = 90; // the center position of servo #1 int yAngle = 90; // the center position of servo #2 int command = COMMAND_NO; unsigned long lastUpdateTime = 0; void setup() { Serial.begin(9600); // Set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); xServo.attach(SERVO_X_PIN); yServo.attach(SERVO_Y_PIN); button.setDebounceTime(50); // set debounce time to 50 milliseconds } void loop() { button.loop(); // MUST call the loop() function first if (millis() - lastUpdateTime > UPDATE_INTERVAL) { lastUpdateTime = millis() ; // read X and Y analog values valueX = analogRead(VRX_PIN); valueY = analogRead(VRY_PIN); // converts the analog value to commands // reset commands command = COMMAND_NO; // check left/right commands if (valueX < LEFT_THRESHOLD) command = command | COMMAND_LEFT; else if (valueX > RIGHT_THRESHOLD) command = command | COMMAND_RIGHT; // check up/down commands if (valueY < UP_THRESHOLD) command = command | COMMAND_UP; else if (valueY > DOWN_THRESHOLD) command = command | COMMAND_DOWN; // NOTE: AT A TIME, THERE MAY BE NO COMMAND, ONE COMMAND OR TWO COMMANDS // print command to serial and process command if (command & COMMAND_LEFT) { Serial.println("COMMAND LEFT"); xAngle--; } if (command & COMMAND_RIGHT) { Serial.println("COMMAND RIGHT"); xAngle++; } if (command & COMMAND_UP) { Serial.println("COMMAND UP"); yAngle--; } if (command & COMMAND_DOWN) { Serial.println("COMMAND DOWN"); yAngle++; } } if (button.isPressed()) { Serial.println("The button is pressed"); xAngle = 90; // the center position of servo #1 yAngle = 90; // the center position of servo #2 } xServo.write(xAngle); // rotate servo motor 1 yServo.write(yAngle); // rotate servo motor 2 // print data to Serial Monitor on Arduino IDE Serial.print("Servo Motor's Angle: "); Serial.print(xAngle); Serial.print("°, "); Serial.print(xAngle); Serial.println("°"); }

Quick Instructions

Click to the Libraries icon on the left bar of the Arduino IDE.
Search “ezButton”, then find the button library by ArduinoGetStarted.com
Click Install button to install ezButton library.

Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP32
Open Serial Monitor
Push the joystick in some direction
See the servo motor's rotation
See the result on Serial Monitor

COM6

Send

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Code Explanation

Read the line-by-line explanation in comment lines of source code!

※ NOTE THAT:

This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a joystick. The ESP32 ADC is good for projects that do NOT need high accuracy. However, for projects that need precise measurements, please note:

The ESP32 ADC is not perfectly accurate and might need calibration for correct results. Each ESP32 board can be a bit different, so you need to calibrate the ADC for each individual board.
Calibration can be difficult, especially for beginners, and might not always give the exact results you want.

For projects that need high precision, consider using an external ADC (e.g ADS1115) with the ESP32 or using an Arduino, which has a more reliable ADC. If you still want to calibrate the ESP32 ADC, refer to ESP32 ADC Calibration Driver

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Function References

Learn More

ESP32 - Joystick

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