JOYSTICKS AND HOW TO USE THEM

Analog sticks are a very common way to transfer human input into electrical signals. Xbox, PlayStation, Nintendo, and so many other game companies use analog joysticks in their game controllers. The following tutorial will go over Joystick Theory and how to correctly implement them into your project.

 

READING THE POTENTIOMETER AND PUSH BUTTONS.

Each joystick using two potentiometers and a push bottom. The potentiometer are positioned in the x and y axis to give you full 2D control like any other game controller. Each potentiometer is hooked up to 5V and ground. The signal pin is read by the Arduino and depending on the position of the joystick, the value coming out of the signal pin can vary anywhere between 5V and 0V.

The Arduino has a 10 Bit ADC, which means that it can sense 1024 different voltages ranging from 0 to 5 volts. When the Joystick is resting in the middle, the Arduino should read a value of 512 (2.5 Volts). When the Joystick is pushed up it should read 1023 (5 Volts) and when pushed down it should read 0 (0 Volts).

The following example uses the Joystick_Basic Example sketch.

The only thing we need to do in the setup function is to setup the pushbuttons for operation. The buttons are connected to pins 4 and 5, and when pressed, they connect the pins to ground. To read when this happens, we need to make pins 4 and 5 an OUTPUT, and then write the pins HIGH to 5 Volts.

pinMode(5, OUTPUT);
pinMode(4, OUTPUT);
digitalWrite(5, HIGH);
digitalWrite(4, HIGH);

The joystick axis’s are very easy to read, as they require no setup and only need the analogRead() function. The left joystick uses A3 and A2, while the right joystick uses A1 and A0. To see if the button on the joystick is pressed, we use the digitalRead() function. Since the pin is set to high, the value will be 1 when the button is not pressed. When the button is pressed, the pin will be connected to ground, and the value will be 0.

 Serial.print("Joystick L: ");
 Serial.print(analogRead(A2)); //Read the Joystick value
 Serial.print("\t");
 Serial.print(analogRead(A3)); //Read the Joystick value
 Serial.print("\t");
 Serial.print(digitalRead(4)); //Read the Button value
 Serial.print("\t");
 
 Serial.print("Joystick R: "); //Read the Joystick value
 Serial.print(analogRead(A0));
 Serial.print("\t");
 Serial.print(analogRead(A1)); //Read the Joystick value
 Serial.print("\t");
 Serial.print(digitalRead(5)); //Read the Button value
 Serial.print("\t");

The values for the analog sticks will range from 0-1023 depending on where you push the stick. When the sticks are resting, the value should read around 512.

You can download the full code from our Downloads page or at the link above.

OFFSET

When you first power up your Pilot RC, the Joystick will most likely not read a value of 512. This is because they are not perfect, but we can compensate for this with software. When the Arduino first starts up, the initial value of the Joysticks should be read so the Arduino knows what the “center” position of the joystick is.


DEADSTICK

The Joysticks have springs that return the center stick to the middle when let go. Unfortunately, this does not mean that the joysticks will return exactly to an analog value of 512. To compensate for this, we add something called deadstick. This is a certain percentage value that if that joystick moves, it will still read the value as no movement. For most cases 5% deadstick is enough, but play around with the value to see what works best with your joysticks.

To see this in action, download our Joystick_Advanced example sketch.