page_title: Atari joystick port
section_title: Paddles
hierarchical_section_title: Atari joystick port / Description / Paddles
caption_attribution_description: The paddle controller for the Atari 2600 video game console. Packed-in with most variants, this controller features a dial versus a joystick, and was mainly meant for Pong-style games. Two paddles were attached to one controller input cable.
context_page_description: The Atari joystick port is a computer port used to connect various gaming controllers to game console and home computer systems in the 1970s to the 1990s. It was originally introduced on the Atari 2600 in 1977 and then used on the Atari 400 and 800 in 1979. It went cross-platform with the Commodore VIC-20 of 1981, and was then used on many following machines from both companies, as well as a growing list of 3rd party machines like the MSX platform and various Sega consoles.
  The port, based on the inexpensive 9-pin D-connector, became a de facto standard through the 1980s and into the 1990s, supported by a wide variety of joysticks and other devices, most commonly paddle controllers, light pens and computer mice. The standard was so engrained that it led to devices like the Kempston Interface that allowed Atari joysticks to be used on the ZX Spectrum. The port was also used for all sorts of non-gaming roles, including the AtariLab interface, modems, numeric keypads, and even a video expansion card.
  By the mid-1990s, the last home computer and game console models using Atari ports - often for both joystick and mouse - were exiting from the markets.
context_section_description: Paddles are analog devices normally used to control horizontal positioning of the player on the screen. On the Atari systems, the paddles were connected in pairs, allowing up to four people to play together on a two-port system.
  The paddles worked by connecting the +5 V line through a potentiometer (pot) and then back into pins 5 and 9, one for each paddle in the pair. Those pins were connected to a capacitor, slowly charging it at a rate set by the position of the pot. When the voltage in the capacitor reached a threshold value, it caused an interrupt in the OS that copied the value of the color clock value from the video hardware. Normally this produced a value from 0 to 228 which was stored as an 8-bit value in the appropriate POT shadow register.
  One advantage to this system was the color clock values provided by the paddle controllers were the same numbers that controlled the horizontal location of sprites, meaning that the programmer could simply copy the value of the pot shadow register into the sprite's horizontal position register and it would appear at the appropriate location on-screen.
caption: Atari paddle controllers were fairly common, although never as widespread as their joysticks.
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