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4.1 Reading Values from a Joystick

In this lesson, we’ll learn how to use a joystick with the Raspberry Pi Pico 2 W to read analog values and detect button presses. A joystick is a common input device that allows you to control movement along two axes (X and Y) and often includes a button when pressed down (Z-axis).

Joystick Module

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	PURCHASE LINK
Pico 2 W Starter Kit	450+	Pico 2 W Kit

You can also buy them separately from the links below.

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Getting to Know Pico 2 W	1
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	Resistor	1(10KΩ)	BUY
6	Joystick Module	1

Understanding the Joystick

A typical joystick module consists of two potentiometers positioned at right angles to each other:

X-axis potentiometer: Measures left-right movement.
Y-axis potentiometer: Measures up-down movement.
Z-axis (Switch): A digital button activated when you press down on the joystick.

By reading the analog values from the X and Y axes, you can determine the position of the joystick. The Z-axis button allows you to detect when the joystick is pressed down.

Schematic

sch_joystick

The SW pin is connected to a 10K pull-up resistor, the reason is to be able to get a stable high level on the SW pin (Z axis) when the joystick is not pressed; otherwise the SW is in a suspended state and the output value may vary between 0/1.

Wiring

wiring_joystick

Writing the Code

Note

You can open the file 4.1_toggle_the_joyostick.ino under the path of pico-2w-kit-main/arduino/4.1_toggle_the_joyostick.
Or copy this code into Arduino IDE.
Don’t forget to select the board(Raspberry Pi Pico) and the correct port before clicking the Upload button.

// Define the pins
const int joystickX = 26;  // GP26 (ADC0) connected to VRx
const int joystickY = 27;  // GP27 (ADC1) connected to VRy
const int joystickSW = 22; // GP22 connected to SW (button)

void setup() {
  // Initialize serial communication at 115200 baud
  Serial.begin(115200);

  // Initialize the joystick switch pin as input
  pinMode(joystickSW, INPUT_PULLUP);

}

void loop() {
  // Read analog values from the joystick
  int xValue = analogRead(joystickX);
  int yValue = analogRead(joystickY);

  // Read the joystick button state
  int buttonState = digitalRead(joystickSW);

  // Print the joystick values to the Serial Monitor
  Serial.print("X: ");
  Serial.print(xValue);
  Serial.print(" | Y: ");
  Serial.print(yValue);
  Serial.print(" | Button: ");
  Serial.println(buttonState == LOW ? "Pressed" : "Released");

  delay(500); // Wait for half a second before the next reading
}

When the code is running and the Serial Monitor is open:

Move the joystick in different directions (left, right, up, down) and observe the X and Y values changing accordingly in the Serial Monitor.
Press the joystick button (Z-axis) and observe the button state changing from “Released” to “Pressed”.

Understanding the Code

Defining Pins:
- joystickX and joystickY: Analog pins connected to the joystick’s X and Y axes.
- joystickSW: Digital pin connected to the joystick’s button (Z-axis).

Setup Function:

Initializes serial communication for debugging and monitoring.
Sets the joystick button pin as input with an internal pull-up resistor to stabilize the input.

void setup() {
  Serial.begin(115200); // Initialize serial communication at 115200 baud
  pinMode(joystickSW, INPUT_PULLUP); // Set joystick button as input with pull-up resistor
}

loop() Function:
- Reading Analog Values:
  
  Reads the current position of the joystick along the X and Y axes. The values range from 0 to 1023, corresponding to the analog voltage levels.
```
int xValue = analogRead(joystickX);
int yValue = analogRead(joystickY);
```
- Reading Button State:
  
  Reads the state of the joystick’s button. LOW indicates pressed, and HIGH indicates released.
```
int buttonState = digitalRead(joystickSW);
```
- Printing to Serial Monitor:
  
  Outputs the current joystick position and button state to the Serial Monitor for debugging and monitoring.
```
Serial.print("X: ");
Serial.print(xValue);
Serial.print(" | Y: ");
Serial.print(yValue);
Serial.print(" | Button: ");
Serial.println(buttonState == LOW ? "Pressed" : "Released");
```

Further Exploration

Mapping Analog Values to Actions:
- Use the joystick’s position to control servos, LEDs, or other actuators based on movement direction and magnitude.
Dead Zone Implementation:
- Implement a dead zone around the center position to prevent unintentional movements due to slight joystick fluctuations.
Combining with Other Sensors:
- Integrate the joystick with other sensors (e.g., accelerometers, distance sensors) to create more complex interactions.
Creating a Game Controller:
- Use multiple joysticks and buttons to build a custom game controller for simple games or robotic control.

Conclusion

In this lesson, you’ve learned how to interface a joystick with the Raspberry Pi Pico to read analog values from the X and Y axes and detect button presses on the Z-axis. This setup can be used as an input method for various projects, including remote controls, robotics, and interactive installations. By understanding how to read and interpret the joystick’s values, you can create responsive and dynamic applications.