The Joystick module is similar to analog joysticks found in gamepads. It is made made by mounting two potentiometers at a 90 degrees angle. The potentiometers are connected to a short stick centered by springs.

Code example:

*
  Analog input, analog output, serial output

 Reads two analog input pins; a T000030 Jopystick Module Analog Sensor connected to I0 and I1, maps the result to a range from 0 to 255
 and uses the result to set the pulsewidth modulation (PWM) two T010111 LED Module connected on O0 and O1.
 Also prints the results to the serial monitor.

 created  7 dec 2010
 by Davide Gomba

 This example code is in the public domain.

 */

 #define O0 11
 #define O1 10
 #define O2 9
 #define O3 6
 #define O4 5
 #define O5 3
 #define I0 A0
 #define I1 A1
 #define I2 A2
 #define I3 A3
 #define I4 A4
 #define I5 A5

// These constants won't change.  They're used to give names
// to the pins used:
const int analogInPin1 = I0;  // Analog input pin that the Joystick's first pin is attached to
const int analogInPin2 = I1;  // Analog input pin that the Joystick's second pin is attached to

const int analogOutPin1= O0; // Analog output pin that the LED is attached to
const int analogOutPin2= O1; // Analog output pin that the LED is attached to

int sensorValue1 = 0;        // value read from the Joystick's first pin
int sensorValue2 = 0;        // value read from the Joystick's second pin

int outputValue1 = 0;        // value output to the PWM (analog out)
int outputValue2 = 0;        // value output to the PWM (analog out)

void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop() {
  // read the both analog in values:
  sensorValue1 = analogRead(analogInPin1);  
  sensorValue2 = analogRead(analogInPin2);  
  // map it to the range of the analog out:
  outputValue1 = map(sensorValue1, 0, 1023, 0, 255);  
  outputValue2 = map(sensorValue2, 0, 1023, 0, 255);
  // change the analog out value:
  analogWrite(analogOutPin1, outputValue1);    
  analogWrite(analogOutPin2, outputValue2);  

  // print the results to the serial monitor:
  Serial.print("Joystick X = " );                      
  Serial.print(sensorValue1);  
  Serial.print("t Joystick Y = " );                      
  Serial.print(sensorValue2);    
  Serial.print("t output 1 = ");      
  Serial.print(outputValue1);  
  Serial.print("t output 2 = ");      
  Serial.println(outputValue2);

  // wait 10 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(10);                    
}