collapseos/kernel/ti/kbd.asm
2019-11-08 20:27:43 -05:00

153 lines
3.7 KiB
NASM

; kbd
;
; Control TI-84+'s keyboard.
;
; *** Constants ***
.equ KBD_PORT 0x01
; Keys that have a special meaning in GetC. All >= 0x80. They are interpreted
; by GetC directly and are never returned as-is.
.equ KBD_KEY_ALPHA 0x80
.equ KBD_KEY_2ND 0x81
; *** Variables ***
; active long-term modifiers, such as a-lock
; bit 0: A-Lock
.equ KBD_MODS KBD_RAMSTART
.equ KBD_RAMEND @+1
; *** Code ***
kbdInit:
xor a
ld (KBD_MODS), a
ret
; Wait for a digit to be pressed and sets the A register ASCII value
; corresponding to that key press.
;
; This routine waits for a key to be pressed, but before that, it waits for
; all keys to be de-pressed. It does that to ensure that two calls to
; waitForKey only go through after two actual key presses (otherwise, the user
; doesn't have enough time to de-press the button before the next waitForKey
; routine registers the same key press as a second one).
;
; Sending 0xff to the port resets the keyboard, and then we have to send groups
; we want to "listen" to, with a 0 in the group bit. Thus, to know if *any* key
; is pressed, we send 0xff to reset the keypad, then 0x00 to select all groups,
; if the result isn't 0xff, at least one key is pressed.
kbdGetC:
push bc
push hl
; During this GetC loop, register C holds the modificators
; bit 0: Alpha
; bit 1: 2nd
; Initial value should be zero, but if A-Lock is on, it's 1
ld a, (KBD_MODS)
and 1
ld c, a
; loop until a digit is pressed
.loop:
ld hl, .dtbl
; we go through the 7 rows of the table
ld b, 7
; is alpha mod enabled?
bit 0, c
jr z, .inner ; unset? skip next
ld hl, .atbl ; set? we're in alpha mode
.inner:
ld a, (hl) ; group mask
call .get
cp 0xff
jr nz, .something
; nothing for that group, let's scan the next group
ld a, 9
call addHL ; go to next row
djnz .inner
; found nothing, loop
jr .loop
.something:
; We have something on that row! Let's find out which char. Register A
; currently contains a mask with the pressed char bit unset.
ld b, 8
inc hl
.findchar:
rrca ; is next bit unset?
jr nc, .gotit ; yes? we have our char!
inc hl
djnz .findchar
.gotit:
ld a, (hl)
or a ; is char 0?
jr z, .loop ; yes? unsupported. loop.
call .debounce
cp KBD_KEY_ALPHA
jr c, .end ; A < 0x80? valid char, return it.
jr z, .handleAlpha
cp KBD_KEY_2ND
jr z, .handle2nd
jp .loop
.handleAlpha:
set 0, c
bit 1, c ; 2nd set?
jp z, .loop ; unset? loop
; we've just hit Alpha with 2nd set. Toggle A-Lock and set Alpha to
; the value A-Lock has.
ld a, (KBD_MODS)
xor 1
ld (KBD_MODS), a
ld c, a
jp .loop
.handle2nd:
set 1, c
jp .loop
.end:
pop hl
pop bc
ret
.get:
ex af, af'
ld a, 0xff
di
out (KBD_PORT), a
ex af, af'
out (KBD_PORT), a
in a, (KBD_PORT)
ei
ret
.debounce:
; wait until all keys are de-pressed
push af ; --> lvl 1
.wait:
xor a
call .get
inc a ; if a was 0xff, will become 0 (nz test)
jr nz, .wait ; non-zero? something is pressed
pop af ; <-- lvl 1
ret
; digits table. each row represents a group. first item is group mask.
; 0 means unsupported. no group 7 because it has no keys.
.dtbl:
.db 0xfe, 0, 0, 0, 0, 0, 0, 0, 0
.db 0xfd, 0x0d, '+' ,'-' ,'*', '/', '^', 0, 0
.db 0xfb, 0, '3', '6', '9', ')', 0, 0, 0
.db 0xf7, '.', '2', '5', '8', '(', 0, 0, 0
.db 0xef, '0', '1', '4', '7', ',', 0, 0, 0
.db 0xdf, 0, 0, 0, 0, 0, 0, 0, KBD_KEY_ALPHA
.db 0xbf, 0, 0, 0, 0, 0, KBD_KEY_2ND, 0, 0x7f
; alpha table. same as .dtbl, for when we're in alpha mode.
.atbl:
.db 0xfe, 0, 0, 0, 0, 0, 0, 0, 0
.db 0xfd, 0x0d, '"' ,'W' ,'R', 'M', 'H', 0, 0
.db 0xfb, '?', 0, 'V', 'Q', 'L', 'G', 0, 0
.db 0xf7, ':', 'Z', 'U', 'P', 'K', 'F', 'C', 0
.db 0xef, '_', 'Y', 'T', 'O', 'J', 'E', 'B', 0
.db 0xdf, 0, 'X', 'S', 'N', 'I', 'D', 'A', KBD_KEY_ALPHA
.db 0xbf, 0, 0, 0, 0, 0, KBD_KEY_2ND, 0, 0x7f