git.sur5r.net Git - cc65/blob - libsrc/atari5200/joy/atr5200std.s

   1 ;
   2 ; Standard joystick driver for the Atari 5200.
   3 ;
   4 ; Christian Groessler, 2014-05-28
   5 ;
   6
   7         .include        "zeropage.inc"
   8
   9         .include        "joy-kernel.inc"
  10         .include        "joy-error.inc"
  11         .include        "atari5200.inc"
  12
  13         .macpack        module
  14
  15
  16 ; ------------------------------------------------------------------------
  17 ; Header. Includes jump table
  18
  19         module_header   _atr5200std_joy
  20
  21 ; Driver signature
  22
  23         .byte   $6A, $6F, $79           ; "joy"
  24         .byte   JOY_API_VERSION         ; Driver API version number
  25
  26 ; Library reference
  27
  28         .addr   $0000
  29
  30 ; Jump table.
  31
  32         .addr   INSTALL
  33         .addr   UNINSTALL
  34         .addr   COUNT
  35         .addr   READJOY
  36
  37 .code
  38
  39 ; ------------------------------------------------------------------------
  40 ; INSTALL routine. Is called after the driver is loaded into memory. If
  41 ; possible, check if the hardware is present and determine the amount of
  42 ; memory available.
  43 ; Must return an JOY_ERR_xx code in a/x.
  44 ;
  45
  46 INSTALL:
  47         lda     #$04            ; enable POT input from the joystick ports, see section "GTIA" in
  48         sta     CONSOL          ;   http://www.atarimuseum.com/videogames/consoles/5200/conv_to_5200.html
  49         lda     #JOY_ERR_OK
  50         ldx     #0
  51 ;       rts                     ; Run into UNINSTALL instead
  52
  53 ; ------------------------------------------------------------------------
  54 ; UNINSTALL routine. Is called before the driver is removed from memory.
  55 ; Can do cleanup or whatever. Must not return anything.
  56 ;
  57
  58 UNINSTALL:
  59         rts
  60
  61
  62 ; ------------------------------------------------------------------------
  63 ; COUNT: Return the total number of available joysticks in a/x.
  64 ;
  65
  66 COUNT:
  67         lda     $FD32           ; check ROM version
  68         cmp     #$E8
  69         bne     @2port
  70         lda     #4
  71         .byte   $2C             ; bit opcode, eats the next 2 bytes
  72 @2port: lda     #2
  73         ldx     #0
  74         rts
  75
  76 ; ------------------------------------------------------------------------
  77 ; READ: Read a particular joystick passed in A.
  78 ;
  79
  80 CENTER  =       228 / 2
  81 SENSIVITY       = 16
  82
  83 READJOY:
  84         and     #3              ; put joystick number in range, just in case
  85         sta     jsnum           ; remember joystick number
  86         tay
  87         asl     a
  88         tax                     ; Joystick number * 2 (0-6) into X, index into ZP shadow registers
  89
  90         lda     #0              ; Initialize return value
  91         cmp     TRIG0,y
  92         bne     @notrg
  93         ora     #$10            ; JOY_BTN
  94
  95 ; Read joystick
  96
  97 @notrg: ldy     PADDL0,x        ; get horizontal position
  98         cpy     #CENTER-SENSIVITY
  99         bcs     @chkleft
 100
 101         ora     #4              ; JOY_LEFT
 102         bne     @updown
 103
 104 @chkleft:
 105         cpy     #CENTER+SENSIVITY
 106         bcc     @updown
 107
 108         ora     #8              ; JOY_RIGHT
 109
 110 @updown:ldy     PADDL0+1,x      ; get vertical position
 111         cpy     #CENTER-SENSIVITY
 112         bcs     @chkdown
 113
 114         ora     #1              ; JOY_UP
 115         bne     @done
 116
 117 @chkdown:
 118         cpy     #CENTER+SENSIVITY
 119         bcc     @done
 120
 121         ora     #2              ; JOY_DOWN
 122
 123 @done:  ldx     #0
 124         ldy     jsnum
 125         cmp     oldval,y
 126         beq     @ret
 127         sta     oldval,y
 128         stx     ATRACT
 129 @ret:   rts
 130
 131 .bss
 132
 133 oldval:.res     4
 134 jsnum: .res     1