View source for Serial RS232 Mouse

Serial RS232 mice could be connected to RS232 interfaces, such like the [[Amstrad Serial Interface]], or to other (in-)compatible Serial interfaces (see [[Peripherals]] for a complete list of known Serial interfaces).

With their hardware based motion-counters, these mice would give much better resolution than the [[AMX Mouse]]. Another approach to use a RS232 mouse would be a mouse interface like the [[AMX Kit]], though that'd cripple the resolution to the AMX level.

== Standard Serial Mouse (most common) ==
A serial mouse should be read at 1200 bauds, 7 data bits, no parity, 1 stop bit (7N1) with DTR and RTS on. For best compatibility, the mouse should output 2 stop bits (so it could be alternately also read as 7N2 or 8N1). When the mouse gets moved, or when a button gets pressed/released, the mouse sends 3 or 4 characters:

  __First Character____________________
  6    First Character Flag (1)
  5    Left Button  (1=Pressed)
  4    Right Button (1=Pressed)
  2-3  Upper 2bit of Vertical Motion
  0-1  Upper 2bit of Horizontal Motion
  __Second Character___________________
  6    Non-first Character Flag (0)
  5-0  Lower 6bit of Horizontal Motion
  __Third Character____________________
  6    Non-first Character Flag (0)
  5-0  Lower 6bit of Vertical Motion
  __Fourth Character (if any)__________
  6    Non-first Character Flag (0)
  5    Middle Button (1=Pressed)
  4    Unused ???
  3-0  Wheel  ???

Additionally, the mouse outputs a detection character (when switching RTS (or DTR?) off and on:

  "M" = Two-Button Mouse (aka "Microsoft" mouse)
  "3" = Three-Button Mouse (aka "Logitech" mouse)
  "Z" = Mouse-Wheel

Normally, the detection response consist of a single character (usually "M"), though some mice have the "M" followed by 11 additional characters of garbage or version information (these extra characters have bit6=0, so after detection, one should ignore all characters until receiving the first data character with bit6=1).

== Mouse Systems Serial Mouse (rare) ==
Accessed at 1200 bauds, just like standard serial mouse, but with 8N1 instead 7N1, and with different data bytes.

  __First Byte_________________________
  7-3  First Byte Code (10000b)
  2    Left? Button   (0=Pressed)
  1    Middle? Button (0=Pressed)
  0    Right? Button  (0=Pressed)
  __Second Byte________________________
  7-0  Horizontal Motion (X1)
  __Third Byte_________________________
  7-0  Vertical Motion   (Y1)
  __Fourth Byte________________________
  7-0  Horizontal Motion (X2)
  __Fifth Byte_________________________
  7-0  Vertical Motion   (Y2)

The strange duplicated 8bit motion values are usually simply added together, ie. X=X1+X2 and Y=Y1+Y2, producing 9bit motion values.

== Notes ==

Mice do return raw mickeys, so effects like double speed threshold must (should) be implemented by software.