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Fall 2020

Circuitry Components In Gaming Controllers: How do video game controllers measure user inputs?

David Engstrom

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Circuitry Components In Gaming Controllers:

How do video game controllers measure user inputs?

Video games rely upon gaming controllers in order to function properly. For a user to interact with a game as intended, each input must be measured and transmitted to the gaming system accurately. There are three main types of gaming controller inputs: standard push buttons, pressure sensitive buttons, and analog sticks. Each type of input requires unique circuitry to be measured and transmitted accurately.

The push button is the most common input on most gaming controllers, and it is also the simplest to measure. Underneath each button is an open circuit. When a button is pressed, it closes the corresponding circuit and allows current to flow through. The buttons are set up in parallel, and each button has a corresponding resistor set up in series with it (Fig.1). A micro- controller inside the game controller measures the current flowing through each resistor [2]. It essentially acts like an ammeter for each input circuit. If any current flows through a resistor, the microcontroller detects it, interprets that the button in series with that resistor is pressed, and 1. Push Buttons in Parallel sends the information to the game. Source: Adapted from [1]

Unlike push buttons, pressure sensitive buttons are analog inputs. Instead of simply determining whether the button is pressed or not, the microcontroller must determine how much pressure is being applied to the button. When a pressure sensitive button is pushed, it applies a force to a pressure sensitive resistor [2]. As the user applies more force to the button, the resistance decreases, and more current flows through the circuit. The microcontroller again acts as an ammeter to measure the current that flows through this resistor, interprets how hard the button is pressed, and sends this information to the game.

2. Analog Stick and Boundary 3. Analog Stick 4. Potentiometer Source: [3] and Potentiometers Source: [5] Source: [4]

The third type of input on a game controller is an analog stick. The user can rotate the analog stick to any location within the circle that bounds it (Fig. 2). In order to measure the location of the analog stick, a set of two potentiometers measures the rotation of the sphere underneath the analog stick (Fig. 3). When the user rotates the analog stick left and right (on the x-axis), it rotates a conductive material known as a wiper, which is connected to a resistive material inside of a potentiometer (Fig. 4). When the wiper rotates to the left, it shortens the effective length of the resistor between the ground pin and the output pin, which decreases the resistance in the circuit. As a result, when the analog stick moves to the left, the current flowing through the potentiometer increases. The microcontroller measures this current like an ammeter to determine the location of the analog stick on the x-axis, and measures the current flowing through the y-axis potentiometer in the same way. It then uses these two currents to transmit the exact location of the analog stick to the game.

Each of these circuits is reliable when it is not interfered with, which is why the way game controllers measure user inputs has remained the same from generation to generation. When the circuits fail, it is typically because dust, grease, or food crumbs get into the controller and interfere with the circuitry. If this gets between a push button and its corresponding circuit, the button stops working. Dust and grease in the analog stick can also prevent the potentiometer circuits from detecting the correct location of the analog stick. Since analog sticks are particularly prone to the problem of dust interference, the PS5 controller casing covers up a larger portion of the sphere under the analog stick, which decreases the likelihood of something getting stuck inside it. This outside interference with interior circuits is still an inherent problem in gaming controllers, however, particularly when they are used for a long time.

A standard controller button sends current through a circuit when it is pushed, acting as a switch. Pressure sensitive buttons put pressure on a force sensitive resistor so that more current flows through the circuit when more pressure is applied. The analog stick rotates two potentiometers, changing their effective resistances and thus changing how much current flows through each circuit. Ultimately, each input acts as its own circuit, and the amount of current that flows through that circuit acts as a measurement of that input, which the game then responds to. Few changes have been made to the input circuits in controllers, because they are effective and reliable. Gaming controller changes typically have more to do with layout and ease of use than the input circuits, but developers must still find ways to ensure that the circuits inside the controller are protected from outside interference during each redesign.

References

[1] Chris. The Perfect Multi-Button Input Resistor Ladder, Ignorant of Things, 1 Jul. 2018. Accessed on: Nov. 17, 2020. www.ignorantofthings.com/2018/07/the-perfect-multi-button-input-resistor.html.

[2] Branch Education. How do Video Game Controllers Work? || Exploring a PS4 Game Controller, Aug. 11, 2020. Accessed on: Nov. 17, 2020. [Video file]. Available: https://www.youtube.com/watch?v=vQesgAtr2e4

[3] Dziura, A. The Gamecube Controller Analog Stick, Wikipedia, 21 Jun. 2006. Accessed on: Nov. 17, 2020. https://en.wikipedia.org/wiki/File:GameCube_Analog_Stick.jpg

[4] Last Minute Engineers. How 2-Axis Joystick Works & Interface with Arduino + Processing, 2020. Accessed on: Nov. 17, 2020. https://lastminuteengineers.com/joystick-interfacing-arduino-processing/

[5] Santos, Rui. Electr onics Basics - How a Potentiometer Works, Jul. 2019. Accessed on: Nov. 17, 2020. Random Nerd Tutorials. https://randomnerdtutorials.com/electronics-basics-how-a-potentiometer-works/