collapseos/kernel/kbd.asm

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; kbd - implement GetC for PS/2 keyboard
;
; It reads raw key codes from a FetchKC routine and returns, if appropriate,
; a proper ASCII char to type. See recipes rc2014/ps2 and sms/kbd.
;
; *** Defines ***
; Pointer to a routine that fetches the last typed keyword in A. Should return
; 0 when nothing was typed.
; KBD_FETCHKC
; *** Variables ***
.equ KBD_SKIP_NEXT KBD_RAMSTART
; Pointer to a routine that fetches the last typed keyword in A. Should return
; 0 when nothing was typed.
.equ KBD_RAMEND KBD_SKIP_NEXT+1
kbdInit:
xor a
ld (KBD_SKIP_NEXT), a
ret
kbdGetC:
call KBD_FETCHKC
or a
jr z, .nothing
; scan code not zero, maybe we have something.
; Do we need to skip it?
push af ; <|
ld a, (KBD_SKIP_NEXT) ;|
or a ; |
jr nz, .skip ; |
pop af ; <|
cp 0x80
jr nc, .outOfBounds
; No need to skip, code within bounds, we have something! Let's see if
; there's a ASCII code associated to it.
push hl ; <|
ld hl, kbdScanCodes ; |
call addHL ; |
ld a, (hl) ; |
pop hl ; <|
or a
jp z, unsetZ ; no code. Keep A at 0, but unset Z
; We have something!
cp a ; ensure Z
ret
.outOfBounds:
; A scan code over 0x80 is out of bounds. Ignore.
; If F0 (break code) or E0 (extended code), we also skip the next code
cp 0xf0
jr z, .skipNext
cp 0xe0
jr z, .skipNext
xor a
jp unsetZ
.skipNext:
ld (KBD_SKIP_NEXT), a
xor a
jp unsetZ
.skip:
pop af ; equilibrate stack
xor a
ld (KBD_SKIP_NEXT), a
jp unsetZ
.nothing:
; We have nothing. Before we go further, we'll wait a bit to give our
; device the time to "breathe". When we're in a "nothing" loop, the z80
; hammers the device really fast and continuously generates interrupts
; on it and it interferes with its other task of reading the keyboard.
push bc
ld b, 0
.wait:
nop
djnz .wait
pop bc
jp unsetZ
; A list of the values associated with the 0x80 possible scan codes of the set
; 2 of the PS/2 keyboard specs. 0 means no value. That value is a character than
; can be read in a GetC routine. No make code in the PS/2 set 2 reaches 0x80.
kbdScanCodes:
; 0x00 1 2 3 4 5 6 7 8 9 a b c d e f
.db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9,'`', 0
; 0x10 9 = TAB
.db 0, 0, 0, 0, 0,'q','1', 0, 0, 0,'z','s','a','w','2', 0
; 0x20 32 = SPACE
.db 0,'c','x','d','e','4','3', 0, 0, 32,'v','f','t','r','5', 0
; 0x30
.db 0,'n','b','h','g','y','6', 0, 0, 0,'m','j','u','7','8', 0
; 0x40 59 = ;
.db 0,',','k','i','o','0','9', 0, 0,'.','/','l', 59,'p','-', 0
; 0x50 13 = RETURN 39 = '
.db 0, 0, 39, 0,'[','=', 0, 0, 0, 0, 13,']', 0,'\', 0, 0
; 0x60 8 = BKSP
.db 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0
; 0x70 27 = ESC
.db 0, 0, 0, 0, 0, 0, 27, 0, 0, 0, 0, 0, 0, 0, 0, 0