Difference between revisions of "Kempston Mouse"
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bit 1: Left Button (active low) | bit 1: Left Button (active low) | ||
bit 2..7: not used. report as high (1) | bit 2..7: not used. report as high (1) | ||
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+ | Number of supported mouse buttons is unknown. It is believed to be 2. The mouse that comes with the interface has two. | ||
== Review (German) == | == Review (German) == |
Revision as of 13:38, 1 October 2015
This mouse is supported by The OCP Art Studio, The Advanced OCP Art Studio and Carrier Command.
Pictures
Technical
The interface described here was loaned to arnoldemu by yoshi.doshi.
PCB has a 50-way edge connector. There is no through connector. The mouse connects via a 9-pin female D-sub (standard joystick socket) which is on the PCB.
The board is labelled "(C) KEMPSTON MICRO AMSTRAD MOUSE I/F" and "ISS B".
The ICs are labelled and are:
IC1 DM74LS00N QUAD 2-INPUT NAND IC2 DM74LS191N SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL (4-bit binary counter) IC3 DM74LS191N SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL (4-bit binary counter) IC4 74LS125APC QUAD 3-STATE BUFFER IC5 DM74LS191N SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL (4-bit binary counter) IC6 DM74LS191N SYNCHRONOUS UP/DOWN COUNTERS WITH DOWN/UP MODE CONTROL (4-bit binary counter) IC7 DM74LS138N 1-OF-8 DECODER/DEMULTIPLEXER IC8 DM74LS257BN 3-STATE QUAD 2-DATA SELECTORS/MULTIPLEXERS IC9 DM74LS257BN 3-STATE QUAD 2-DATA SELECTORS/MULTIPLEXERS
The mouse that comes with the interface has 2 buttons. It is a ball mouse. Unknown brand. Green label reads "Q.C. PASSED. MADE IN TAIWAN. R. O. C.". Mouse has 9-pin DIN like a joystick. Unknown if compatible with Atari ST or Amiga or neither.
The schematics and PCB are 90% the same as the Spectrum's. They differ in the port decoding.
Port decoding to be confirmed.
FBEE is xxxx x0x1 xxx0 xxx0 FBEF is xxxx x0x1 xxx0 xxx1 FAEF is xxxx x0x0 xxx0 xxxx
In Spectrum interface A10 chooses X,Y. On CPC interface A0 chooses X,Y. In Spectrum interface A8 chooses buttons or directions. On CPC interface A8 also chooses this.
Position:
Port FBEEh READ: Kempston Mouse 8 bit X position (left: -ve, right: +ve) Port FBEFh READ: Kempston Mouse 8 bit Y position (up: +ve, down: -ve)
NOTE:
- The position values aren't reset after reading.
- The position values do not change if the mouse doesn't move in that
- Position values wrap around e.g. when moving left with movement speed of 1, 0 wraps around to ff (0-1 -> ff)
and when moving right with movement speed of 1, ff wraps around to 0 (ff+1->0)
To calculated the distance moved since last read subtract the new value read from the previous value read and AND with ff. The value is the amount of movement. 0 means no movement. -ve means moving left/down, +ve means right/up.
dist=new-old, old=new whereas, dist=00h : no move dist=+01h..+7Fh moved right/up dist=-01h..-80h moved left/down
Buttons:
Port FAEFh READ: Kempston Mouse Buttons bit 0: Right Button (active low) bit 1: Left Button (active low) bit 2..7: not used. report as high (1)
Number of supported mouse buttons is unknown. It is believed to be 2. The mouse that comes with the interface has two.
Review (German)
From an article about the "Amstrad Consumer Show" in German magazine "Happy Computer 12/1986":
- "Bewundern Sie auch die Maussteuerung eines Atari ST oder eines Schneider PC? Bei Kempston gibt es für 69,95 Pfund auch für Ihren CPC oder Joyce so eine komfortable Benutzeroberfläche. Die Maus entspricht dabei völlig dem Standard mit zwei unabhängigen Tasten. Das mitgelieferte Desktop-Programm braucht sich vor den Brüdern auf 16-Bit-Computern nicht zu verstecken."
Get mouse position on screen
Calculating the mouse position from the information given on the Kempston mouse ports is easy.
We will proceed in 2 steps:
1. Calculate mouse pointer location on a virtual screen that has a 640*400 resolution. 2. Translate position from the virtual screen to the current CPC screen mode.
Here is the algorithm in pseudo-code:
// initMouse initializes variables and centers the mouse pointer on screen function initMouse() { maxX = 639; maxY = 399; // centering the mouse pointer on the screen virtualX = maxX >> 1; // virtualX = maxX/2 virtualY = maxY >> 1; // virtualY = maxY/2 // store raw mouse values oldX = inp(&FBEE); oldY = inp(&FBEF); // get mouse pointer position refreshMouse(); }
// refreshMouse has to be called before you redraw the mouse pointer (and ideally on every frame) function refreshMouse() { // get raw mouse values rawX = inp(&FBEE); rawY = inp(&FBEF); // get the relative mouse displacement since last call deltaX = rawX - oldX; deltaY = rawY - oldY; // store raw mouse values oldX = rawX; oldY = rawY; // calculate new unclipped virtual position virtualX = virtualX + deltaX; virtualY = virtualY - deltaY; // Kempston mouse Y-axis is inverted compared to screen coordinates! // perform clipping if (virtualX < 0) then virtualX = 0; else if (virtualX > maxX) then virtualX = maxX; if (virtualY < 0) then virtualY = 0; else if (virtualY > maxY) then virtualY = maxY; // now we translate position from the virtual screen to the current CPC screen mode mouseY = virtualY >> 1; // mouseY = virtualY/2 if (mode2) then mouseX = virtualX; else if (mode1) then mouseX = virtualX >> 1; // mouseX = virtualX/2 else if (mode0) then mouseX = virtualX >> 2; // mouseX = virtualX/4 }