92 lines
2.3 KiB
NASM
92 lines
2.3 KiB
NASM
; kbd
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;
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; Control TI-84+'s keyboard.
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;
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; *** Constants ***
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.equ KBD_PORT 0x01
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; *** Code ***
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; Wait for a digit to be pressed and sets the A register ASCII value
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; corresponding to that key press.
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;
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; This routine waits for a key to be pressed, but before that, it waits for
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; all keys to be de-pressed. It does that to ensure that two calls to
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; waitForKey only go through after two actual key presses (otherwise, the user
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; doesn't have enough time to de-press the button before the next waitForKey
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; routine registers the same key press as a second one).
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;
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; Sending 0xff to the port resets the keyboard, and then we have to send groups
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; we want to "listen" to, with a 0 in the group bit. Thus, to know if *any* key
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; is pressed, we send 0xff to reset the keypad, then 0x00 to select all groups,
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; if the result isn't 0xff, at least one key is pressed.
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kbdGetC:
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push bc
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push hl
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; loop until a digit is pressed
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.loop:
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ld hl, .dtbl
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; we go through the 7 rows of the table
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ld b, 7
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.inner:
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ld a, (hl) ; group mask
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call .get
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cp 0xff
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jr nz, .something
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; nothing for that group, let's scan the next group
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ld a, 9
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call addHL ; go to next row
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djnz .inner
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; found nothing, loop
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jr .loop
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.something:
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; We have something on that row! Let's find out which char. Register A
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; currently contains a mask with the pressed char bit unset.
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ld b, 8
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inc hl
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.findchar:
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rrca ; is next bit unset?
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jr nc, .gotit ; yes? we have our char!
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inc hl
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djnz .findchar
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.gotit:
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ld a, (hl)
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or a ; is char 0?
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jr z, .loop ; yes? unsupported. loop.
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; wait until all keys are de-pressed
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push af ; --> lvl 1
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.wait:
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xor a
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call .get
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inc a ; if a was 0xff, will become 0 (nz test)
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jr nz, .wait ; non-zero? something is pressed
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pop af ; <-- lvl 1
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pop hl
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pop bc
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ret
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.get:
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ex af, af'
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ld a, 0xff
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di
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out (KBD_PORT), a
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ex af, af'
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out (KBD_PORT), a
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in a, (KBD_PORT)
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ei
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ret
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; digits table. each row represents a group. first item is group mask.
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; 0 means unsupported. no group 7 because it has no keys.
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.dtbl:
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.db 0xfe, 0, 0, 0, 0, 0, 0, 0, 0
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.db 0xfd, 0x0d, '+' ,'-' ,'*', '/', '^', 0, 0
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.db 0xfb, 0, '3', '6', '9', ')', 0, 0, 0
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.db 0xf7, '.', '2', '5', '8', '(', 0, 0, 0
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.db 0xef, '0', '1', '4', '7', ',', 0, 0, 0
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.db 0xdf, 0, 0, 0, 0, 0, 0, 0, 0
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.db 0xbf, 0, 0, 0, 0, 0, 0, 0, 0x7f
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