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cc65/libsrc/creativision/joy/creativision-stdjoy.s

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;
; Standard joystick driver for the Creativision.
;
; 2017-03-08, Christian Groessler
; 2021-06-01, Greg King
;
.include "zeropage.inc"
.include "joy-kernel.inc"
.include "joy-error.inc"
.include "creativision.inc"
.macpack module
buttons := tmp2
; ------------------------------------------------------------------------
; Header. Includes jump table
module_header _creativisionstd_joy
; Driver signature
.byte $6A, $6F, $79 ; "joy"
.byte JOY_API_VERSION ; Driver API version number
; Library reference
.addr $0000
; Jump table.
.addr INSTALL
.addr UNINSTALL
.addr COUNT
.addr READJOY
; ------------------------------------------------------------------------
; Constants
JOY_COUNT = 2 ; Number of joysticks we support
; Symbolic names for joystick masks (similar names to the macros in joystick.h,
; with the same values as the masks in creativision.h)
JOY_UP = $10
JOY_DOWN = $04
JOY_LEFT = $20
JOY_RIGHT = $08
.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 #JOY_ERR_OK
ldx #>$0000
; rts ; Fall through
; ------------------------------------------------------------------------
; 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.
;
READJOY: lsr a ; Get joystick number
bcs READJOY_1 ; Read right joystick
; Read left joystick
ldx ZP_JOY0_DIR
lda ZP_JOY0_BUTTONS
bcc convert ; Convert joystick state to cc65 values
; Read right joystick
READJOY_1: ldx ZP_JOY1_DIR
lda ZP_JOY1_BUTTONS
lsr a
lsr a
;jmp convert ; Convert joystick state to cc65 values
; Fall thru...
; ------------------------------------------------------------------------
; convert: make runtime lib-compatible values
; inputs:
; A - buttons
; X - direction
;
convert:
; ------
; buttons:
; Port values are for the left-hand joystick (right-hand joystick
; values were shifted to the right to be identical).
; Why are there two bits indicating a pressed trigger?
; According to the "Second book of programs for the Dick Smith Wizard"
; (pg. 88ff), the left-hand button gives the value of
; %00010001 and the right-hand button gives %00100010
; Why two bits? Can there be cases that just one of those bits is set?
; Until those questions have been answered, we only use the lower two
; bits, and ignore the upper ones.
and #%00000011 ; Button status came in A, strip high bits
sta buttons
; ------
; direction:
; CV has a 16-direction joystick.
;
; Port values: (compass points)
; N - $49 - %01001001
; NNE - $48 - %01001000
; NE - $47 - %01000111
; ENE - $46 - %01000110
; E - $45 - %01000101
; ESE - $44 - %01000100
; SE - $43 - %01000011
; SSE - $42 - %01000010
; S - $41 - %01000001
; SSW - $40 - %01000000
; SW - $4F - %01001111
; WSW - $4E - %01001110
; W - $4D - %01001101
; WNW - $4C - %01001100
; NW - $4B - %01001011
; NNW - $4A - %01001010
; center - $00 - %00000000
;
; Mapping to cc65 definitions (4-direction joystick with 8 possible directions thru combinations):
; N, E, S, W -> JOY_UP, JOY_RIGHT, JOY_DOWN, JOY_LEFT
; NE, SE, SW, NW -> (JOY_UP | JOY_RIGHT), (JOY_DOWN | JOY_RIGHT), (JOY_DOWN | JOY_LEFT), (JOY_UP | JOY_LEFT)
; NNE, ENE, ESE, SSE, SSW, WSW, WNW, NNW:
; toggle between the straight and diagonal directions for each call, e.g.,
; NNE:
; call to READJOY: return JOY_UP | JOY_RIGHT
; call to READJOY: return JOY_UP
; call to READJOY: return JOY_UP | JOY_RIGHT
; call to READJOY: return JOY_UP
; call to READJOY: return JOY_UP | JOY_RIGHT
; etc.
txa ; Move direction status into A
beq done ; Center position (no bits are set), nothing to do
and #$0F ; Get rid of the "$40" bit
lsr a ; Is it "three-letter" direction (NNE, ENE, etc.)?
tax ; Create index into table
bcc special ; Yes (bit #0 was zero)
lda dirtable,x
done: ora buttons ; Include button bits
ldx #>$0000
rts
; NNE, ENE, ESE, SSE, SSW, WSW, WNW, NNW
special: lda toggle ; Toggle the flag
eor #$01
sta toggle
bne spec_1 ; Flag is 1, use spectable_1 entry
lda spectable_0,x
bne done ; Jump always
spec_1: lda spectable_1,x
bne done ; Jump always
; ------------------------------------------------------------------------
;
.rodata
; A mapping table of "port values" to "cc65 values"
; Port value had been shifted one bit to the right (range 0..7)
dirtable: .byte JOY_DOWN ; S
.byte JOY_DOWN | JOY_RIGHT ; SE
.byte JOY_RIGHT ; E
.byte JOY_UP | JOY_RIGHT ; NE
.byte JOY_UP ; N
.byte JOY_UP | JOY_LEFT ; NW
.byte JOY_LEFT ; W
.byte JOY_DOWN | JOY_LEFT ; SW
; Two "special" mapping tables for three-letter directions (NNE, etc.)
spectable_0: .byte JOY_DOWN ; SSW
.byte JOY_DOWN ; SSE
.byte JOY_RIGHT ; ESE
.byte JOY_RIGHT ; ENE
.byte JOY_UP ; NNE
.byte JOY_UP ; NNW
.byte JOY_LEFT ; WNW
.byte JOY_LEFT ; WSW
spectable_1: .byte JOY_DOWN | JOY_LEFT ; SSW
.byte JOY_DOWN | JOY_RIGHT ; SSE
.byte JOY_DOWN | JOY_RIGHT ; ESE
.byte JOY_UP | JOY_RIGHT ; ENE
.byte JOY_UP | JOY_RIGHT ; NNE
.byte JOY_UP | JOY_LEFT ; NNW
.byte JOY_UP | JOY_LEFT ; WNW
.byte JOY_DOWN | JOY_LEFT ; WSW
; ------------------------------------------------------------------------
;
.bss
toggle: .res 1
.end
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