mirror of
https://github.com/hsoft/collapseos.git
synced 2024-12-26 18:38:05 +11:00
167 lines
3.6 KiB
NASM
167 lines
3.6 KiB
NASM
; pad - read input from MD controller
|
|
;
|
|
; Conveniently expose an API to read the status of a MD pad A. Moreover,
|
|
; implement a mechanism to input arbitrary characters from it. It goes as
|
|
; follow:
|
|
;
|
|
; * Direction pad select characters. Up/Down move by one, Left/Right move by 5\
|
|
; * Start acts like Return
|
|
; * A acts like Backspace
|
|
; * B changes "character class": lowercase, uppercase, numbers, special chars.
|
|
; The space character is the first among special chars.
|
|
; * C confirms letter selection
|
|
;
|
|
; *** Consts ***
|
|
;
|
|
.equ PAD_CTLPORT 0x3f
|
|
.equ PAD_D1PORT 0xdc
|
|
|
|
.equ PAD_UP 0
|
|
.equ PAD_DOWN 1
|
|
.equ PAD_LEFT 2
|
|
.equ PAD_RIGHT 3
|
|
.equ PAD_BUTB 4
|
|
.equ PAD_BUTC 5
|
|
.equ PAD_BUTA 6
|
|
.equ PAD_START 7
|
|
|
|
; *** Variables ***
|
|
;
|
|
; Button status of last padUpdateSel call. Used for debouncing.
|
|
.equ PAD_SELSTAT PAD_RAMSTART
|
|
; Button status of last padGetC call.
|
|
.equ PAD_GETCSTAT PAD_SELSTAT+1
|
|
; Current selection "class". 0 = lowcase, 1 = upcase, 2 = num, 3 = symbols
|
|
.equ PAD_SELCLASS PAD_GETCSTAT+1
|
|
; Current selected character
|
|
.equ PAD_SELCHR PAD_SELCLASS+1
|
|
; Whether current sel is "new", that is, that its value has never been fetched
|
|
; though padUpdateSel. This flag is set when "avancing" in GetC and also on
|
|
; module init.
|
|
.equ PAD_SELNEW PAD_SELCHR+1
|
|
.equ PAD_RAMEND PAD_SELNEW+1
|
|
|
|
; *** Code ***
|
|
|
|
padInit:
|
|
ld a, 0xff
|
|
ld (PAD_SELSTAT), a
|
|
ld (PAD_GETCSTAT), a
|
|
ld (PAD_SELNEW), a
|
|
xor a
|
|
ld (PAD_SELCLASS), a
|
|
ld a, 'a'
|
|
ld (PAD_SELCHR), a
|
|
ret
|
|
|
|
; Put status for port A in register A. Bits, from MSB to LSB:
|
|
; Start - A - C - B - Right - Left - Down - Up
|
|
; Each bit is high when button is unpressed and low if button is pressed. For
|
|
; example, when no button is pressed, 0xff is returned.
|
|
padStatus:
|
|
; This logic below is for the Genesis controller, which is modal. TH is
|
|
; an output pin that swiches the meaning of TL and TR. When TH is high
|
|
; (unselected), TL = Button B and TR = Button C. When TH is low
|
|
; (selected), TL = Button A and TR = Start.
|
|
push bc
|
|
ld a, 0b11111101 ; TH output, unselected
|
|
out (PAD_CTLPORT), a
|
|
in a, (PAD_D1PORT)
|
|
and 0x3f ; low 6 bits are good
|
|
ld b, a ; let's store them
|
|
; Start and A are returned when TH is selected, in bits 5 and 4. Well
|
|
; get them, left-shift them and integrate them to B.
|
|
ld a, 0b11011101 ; TH output, selected
|
|
out (PAD_CTLPORT), a
|
|
in a, (PAD_D1PORT)
|
|
and 0b00110000
|
|
sla a
|
|
sla a
|
|
or b
|
|
pop bc
|
|
ret
|
|
|
|
; From a pad status in A, update current char selection and return it.
|
|
; Returns the same Z as padStatus: set if unchanged, unset if changed
|
|
padUpdateSel:
|
|
; special case: when selnew is set, always return current sel and
|
|
; disable selnew
|
|
ld a, (PAD_SELNEW)
|
|
or a
|
|
jr z, .notnew
|
|
; selection is new, return it
|
|
xor a
|
|
ld (PAD_SELNEW), a
|
|
ld a, (PAD_SELCHR)
|
|
jp unsetZ
|
|
.notnew:
|
|
call padStatus
|
|
push hl
|
|
ld hl, PAD_SELSTAT
|
|
cp (hl)
|
|
ld (hl), a
|
|
pop hl
|
|
jr z, .nothing ; nothing changed
|
|
bit PAD_UP, a
|
|
jr z, .up
|
|
bit PAD_DOWN, a
|
|
jr z, .down
|
|
bit PAD_LEFT, a
|
|
jr z, .left
|
|
bit PAD_RIGHT, a
|
|
jr z, .right
|
|
jr .nothing
|
|
.up:
|
|
ld a, (PAD_SELCHR)
|
|
inc a
|
|
jr .setchr
|
|
.down:
|
|
ld a, (PAD_SELCHR)
|
|
dec a
|
|
jr .setchr
|
|
.left:
|
|
ld a, (PAD_SELCHR)
|
|
dec a \ dec a \ dec a \ dec a \ dec a
|
|
jr .setchr
|
|
.right:
|
|
ld a, (PAD_SELCHR)
|
|
inc a \ inc a \ inc a \ inc a \ inc a
|
|
jr .setchr
|
|
.setchr:
|
|
ld (PAD_SELCHR), a
|
|
jp unsetZ
|
|
.nothing:
|
|
cp a ; ensure Z
|
|
ld a, (PAD_SELCHR)
|
|
ret
|
|
|
|
padGetC:
|
|
call padStatus
|
|
push hl
|
|
ld hl, PAD_GETCSTAT
|
|
cp (hl)
|
|
ld (hl), a
|
|
pop hl
|
|
jp z, unsetZ ; nothing changed
|
|
bit PAD_BUTC, a
|
|
jr z, .advance
|
|
bit PAD_BUTA, a
|
|
jr z, .backspace
|
|
bit PAD_START, a
|
|
jr z, .return
|
|
jp unsetZ
|
|
.advance:
|
|
ld a, 1
|
|
ld (PAD_SELNEW), a
|
|
ld a, (PAD_SELCHR)
|
|
cp a
|
|
ret
|
|
.backspace:
|
|
ld a, ASCII_BS
|
|
cp a
|
|
ret
|
|
.return:
|
|
ld a, ASCII_LF
|
|
cp a
|
|
ret
|