Editing Atari interface (section)

==Mice and trackballs==
Typical ball-mice and trackballs have [[opto-mechanical sensor]]s for the X and Y axes, each producing two pulse trains that are 90 degrees out of phase with one-another. (The same as a 2-bit Gray code, also called "quadrature encoding")

===8-bit machines===
It was problematic for an 8-bit machine with no dedicated hardware to read quadrature code fast enough and still have time for other processing.

Atari's ''Trak-Ball'' controllers for the Atari 2600 converted the quadrature code into either joystick input or into direction and motion pulses.<ref>AtariMania — [http://www.atarimania.com/documents/Atari-CX22-Trakball-Field-Service-Manual.pdf Atari CX22 Trakball Field Service Manual]. Rev 01. Nov 1983. Retrieved 2018-06-05.</ref>
The latter signalling meant that a missed reading would only cause failing to move one (or more) steps instead of moving in the wrong direction.
Mice and trackballs for Atari's 8-bit home computers used the same type of signalling.

[[File:Amiga Mouse.jpg|thumb|175px|right|First iteration of Commodore Amiga mouse, styled the same as the mice for the Commodore 64]]
Commodore's own mice either emulated a joystick or used potentiometers (like [[#Paddles|paddles]]) that wrapped around.

Mice for J-PC machines have instead internal logic for reading the encoders, with the obvious drawback that they were more expensive. The mouse presents X and Y byte-counters as nybbles on pins 1-4 in alternating order, but the other pins follow the J-PC pinout which does not work with the Atari-standard without an adaptor. 
The ''NEOS Mouse'' for the Commodore 64 was in essence a J-PC mouse, with the pinout changed to work with the Commodore 64.
<ref>C64 Wiki—[https://www.c64-wiki.com/wiki/NEOS_Mouse NEOS Mouse]. Dated 2017-05-09. Retrieved 2018-06-07</ref>

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===Atari ST and Amiga===
Mice for both the [[Commodore Amiga|Amiga]] and [[Atari ST]] are [[Bus mouse|Bus mice]] which produce quadrature signals and buttons to different pins.
Some third-party mice have support for both systems, selected via a switch that only changes which pins the quadrature signals go to.
The left mouse button is wired the same as a joystick's Fire button and the other button(s)s also short to ground.

On the Amiga, signals are interpreted by circuitry in its custom chipset and there is hardware support for a mouse in each port. A second Amiga mouse can be used only in some two-player games, however.
On the Atari, one mouse can be plugged into a dedicated mouse/joystick port on the keyboard, which is interpreted by the keyboard's microcontroller. A curious detail is that the Atari ST's right mouse-button is wired to and read as the other port's Fire button.

Amigas typically have two-button mice. Commodore made a three-button mouse only for the Amiga 3000UX that ran Amiga [[UNIX]] but many third-party Amiga mice also came with middle-button.
In the late 1990s, there appeared third-party Amiga mice with [[scroll wheel]]s, using varying current on the POTX line (pin 5) for input which required a special driver. The third button is represented in a new way.<ref name="micromysv3">Micromys.de—[http://micromys.de/Amiga_devel.htm Micromys support page - Amiga mouse mode with wheel support]. Dated 2000. Retrieved 2019-03-24</ref>

The Amiga's operating system provides (when booted into Workbench) also [[mouse keys]] as combinations together with the [[Amiga key]]s.

===PC bus mouse===
When Atari and Commodore started offering [[IBM Personal Computer|IBM]]-compatible PCs with built-in mouse support, they reused their mice and ports from the Atari ST and Amiga respectively as [[Bus mouse|bus mice]].
Atari's "STM1" mouse got relabelled as "PCM1" for use with Atari PCs.<ref name="ataripcnetpc3">AtariPC.net—[http://www.ataripc.net/pc3-8088/ PC3 8088]. Retrieved 2019-03-24</ref>.
The Atari PC's mouse ports support a third (middle) mouse button
<ref name="ataripcom">Atari PC Owner's manual [http://www.ataripc.net/files/documents/archives/ownersmanual/Atari%20PC%20Owners%20Manual%20-%20English.pdf Scan on ataripc.net]. Page 65. Dated 1987. Retrieved 2019-03-24</ref>, whereas the Atari ST does not.
Amiga-compatible mouse ports were standard (on the motherboard) on the Commodore PC10-III and PC20-III.<ref>Ancient Electronics blog—[https://ancientelectronics.wordpress.com/2015/06/17/commodore-colt-commodore-pc10-iii-pc20-iii/ Commodore Colt (Commodore PC10-III, PC20-III)</ref>

Amstrad PC-1512<ref name="amstradpc1512">[http://www.seasip.info/AmstradXT/1512tech/section1.html Amstrad PC1512 Technical Reference Manual]. Copy on John Elliott's homepage, retrieved 2019-03-29</ref>, PC-1640<ref name="amstradpc1640">[http://www.seasip.info/AmstradXT/1640tech/section1.html AMSTRAD PC1640 TECHNICAL MANUAL]. Copy on John Elliott's homepage, retrieved 2019-03-29</ref> and Sinclair PC-200<ref name="sinclairpc200">The Vintage Computer Club Malta—[https://web.computersmuseum.com/collection/sinclair/sinclair-pc-200/ SINCLAIR PC 200]. Retrieved 2019-03-26</ref> (made by Amstrad) got a dedicated 9-pin port for a [[bus mouse]]. They use almost the Atari ST pinout except that the horizontal axis is flipped. A curious detail is that the two mouse buttons' lines were fed to the keyboard and reported by it as key codes.

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