Editing Atari interface (section)

==Light pens and light guns==
Atari 2600, 7800 and 8-bit computers and Commodore's C64 and Amiga support [[light pen]]s and [[light gun]]s through a line in one port connected to the video chip.

A light pen has a pressure-switch at the tip to tell the host when to read the screen position where as a light gun used a finger-operated trigger for the same purpose.
The light sensor shared the same pin as a joystick's button, so the pressure had to use a different pin and that differed a bit between devices.

Light pens and light guns for the Atari 8-bit computers grounded pin 1 (up)
<ref>Atari HQ: [http://www.atarihq.com/atcomp/xegs.html ATARI XEGS INFORMATION].</ref>
For the Commodore 64, most light pens also used pin 1 <ref name="c64wikilightpen">C64 Wiki — [https://www.c64-wiki.com/wiki/Light_pen Light pen]. Dated 2017-05-26. Retrieved 2018-05-24</ref> but the most popular light guns shorted pin 5 (POTY) to +5V.<ref>Projects of Jan Derogee—[http://home.kpn.nl/bderogee1980/projects/lightgun/Magnum_light_phaser.html C64 Lightguns/Magnum light phaser ( and compatible models )]. Retrieved 2018-06-11</ref>
Stack's ''light rifle'' grounded pin 3 (left)<ref>Projects of Jan Derogee—[http://home.kpn.nl/bderogee1980/projects/lightgun/StackLightRifle.html C64 Lightguns/Stack light rifle]. Retrieved 2018-06-11</ref>.
Devices for the Amiga were supposed to use pin 5<ref name="elowaradcd"/>.

<!-- TODO: Check if Datel light pen and Inkwell Light Pen comply to these...-->

Sega ''lightphasers'' had a different pinout but could be used with an adaptor or mod.<ref>64HDD—[http://www.64hdd.com/projects/c64-proj3.html#lightgun Commodore™ C64 Hardware Projects: Light gun]. Nicholas Coplin.</ref>

The ''Gun stick'' light gun for the C64 instead worked like the light gun on the Nintendo Entertainment System: when the trigger was pressed, the screen would turn black except for a white field for ''one'' valid target at a time.<ref>Projects of Jan Derogee—[http://home.kpn.nl/bderogee1980/projects/lightgun/Gun_stick.html C64 Lightguns/Gun stick]. Retrived 2018-06-11</ref>