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Alternative joystick interface

diff --git a/libsrc/atmos/joy/atmos-ijk.s b/libsrc/atmos/joy/atmos-ijk.s
new file mode 100644 (file)
index 0000000..f59f6b9
--- /dev/null
+++ b/libsrc/atmos/joy/atmos-ijk.s
@@ -0,0 +1,146 @@
+;
+; IJK joystick driver for the Atmos
+; Can be used multiple times when statically linked to the application.
+;
+; 2002-12-20, Based on Ullrich von Bassewitz's code.
+; 2017-11-01, Stefan Haubenthal
+;
+
+        .include        "joy-kernel.inc"
+        .include        "joy-error.inc"
+        .include        "atmos.inc"
+
+        .macpack        module
+
+
+; ------------------------------------------------------------------------
+; Header. Includes jump table
+
+        module_header   _atmos_ijk_joy
+
+; Driver signature
+
+        .byte   $6A, $6F, $79           ; "joy"
+        .byte   JOY_API_VERSION         ; Driver API version number
+
+; Library reference
+
+        .addr   $0000
+
+; Button state masks (8 values)
+
+        .byte   $10                     ; JOY_UP
+        .byte   $08                     ; JOY_DOWN
+        .byte   $01                     ; JOY_LEFT
+        .byte   $02                     ; JOY_RIGHT
+        .byte   $20                     ; JOY_FIRE
+        .byte   $00                     ; Future expansion
+        .byte   $00                     ; Future expansion
+        .byte   $00                     ; Future expansion
+
+; Jump table.
+
+        .addr   INSTALL
+        .addr   UNINSTALL
+        .addr   COUNT
+        .addr   READ
+        .addr   0                       ; IRQ entry unused
+
+; ------------------------------------------------------------------------
+; Constants
+
+JOY_COUNT       = 2             ; Number of joysticks we support
+
+.code
+
+; ------------------------------------------------------------------------
+; INSTALL routine. Is called after the driver is loaded into memory. If
+; possible, check if the hardware is present and determine the amount of
+; memory available.
+; Must return an JOY_ERR_xx code in a/x.
+;
+
+INSTALL:
+        lda     #%11000000
+        sta     VIA::DDRA
+        sta     VIA::PRA
+        lda     VIA::PRA
+        and     #%00100000
+        bne     ijkPresent
+        lda     #<JOY_ERR_NO_DEVICE
+        .byte   $2C             ; Skip next opcode
+ijkPresent:
+        lda     #<JOY_ERR_OK
+        ldx     #>JOY_ERR_OK
+;       rts                     ; Run into UNINSTALL instead
+
+; ------------------------------------------------------------------------
+; UNINSTALL routine. Is called before the driver is removed from memory.
+; Can do cleanup or whatever. Must not return anything.
+;
+
+UNINSTALL:
+        rts
+
+
+; ------------------------------------------------------------------------
+; COUNT: Return the total number of available joysticks in a/x.
+;
+
+COUNT:
+        lda     #<JOY_COUNT
+        ldx     #>JOY_COUNT
+        rts
+
+; ------------------------------------------------------------------------
+; READ: Read a particular joystick passed in A.
+;
+
+READ:
+        bne     right
+
+        ; Ensure Printer Strobe is set to Output
+        lda     #%10110111
+        sta     VIA::DDRB
+        ; Set Strobe Low
+        lda     #%00000000
+        sta     VIA::PRB
+        ; Set Top two bits of PortA to Output and rest as Input
+        lda     #%11000000
+        sta     VIA::DDRA
+
+        ; Select Left Joystick
+        lda     #%01111111
+        sta     VIA::PRA
+        ; Read back Left Joystick state
+        lda     VIA::PRA
+        ; Mask out unused bits
+        and     #%00011111
+        ; Invert Bits
+        eor     #%00011111
+        ; Index table to conform to Generic Format
+        tax
+        lda     GenericIJKBits,X
+        bne     L1
+
+right:
+        ; Select Right Joystick
+        lda     #%10111111
+        sta     VIA::PRA
+        ; Read back Right Joystick state and rejig bits
+        lda     VIA::PRA
+        and     #%00011111
+        eor     #%00011111
+        tax
+        lda     GenericIJKBits,X
+
+        ; Restore VIA PortA state
+L1:     ldx     #%11111111
+        stx     VIA::DDRA
+        inx     ; x=0
+        rts
+
+.rodata
+GenericIJKBits:
+        .byte   0,2,1,3,32,34,33,0,8,10,9,0,40,42,41,0
+        .byte   16,18,17,0,48,50,49,0,0,0,0,0,0,0,0,0