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- ; first draft keyboard reading routine to replace some BASIC
- ;
- ; Kempston mouse and joystick not implemented yet
- ; DEBUG CODE - PRESS 0 TO RETURN TO BASIC
- ; Q,A,O,P move cursor
- ; SPACE, ENTER, 1 and 0 are detected and indicated
- ; K and J alter cursor speed
- ;
- org 30000 ; everyone has to start somewhere
- jp _init ; for ease of use in BASIC, we're going to keep
- ; our variables at the start of the routine, so
- ; jump up out of the way, this is probably sub-optimal
- ;
- action defb 0 ; we store our 'action' indicator
- xpos defb 128, 0 ; have 2 bytes to make BC printing easy for now
- ypos defb 88, 0 ; have 2 bytes to make BC printing easy for now
- speed defb 1, 0 ; have 2 bytes to make BC printing easy for now
- ;
- ;
- ; screen init code
- ; ================
- _init : ld a, 71 ; black paper, white ink
- ld (23693), a ; save attribs
- xor a ; a = 0
- call 8859 ; clear the screen
- call 3503 ; setup channel 2
- ;
- ;
- ; main code
- ; =========
- _mainloop: xor a ; a = 0
- ld (action), a ; reset our action indicator
- ld bc, 57342 ; keyrow for Y-P
- in a,(c) ; get value
- push af ; save it so we don't need to re-read in a moment
- cp 190 ; P key pressed?
- call z, moveright ; move cursor right
- pop af ; get action back
- cp 189 ; O key pressed?
- call z, moveleft ; move cursor left
- ld bc, 64510 ; keyrow for Q-T
- in a,(c) ; get value
- cp 190 ; Q key pressed?
- call z, movedown ; move cursor down (towards origin)
- ld bc, 65022 ; keyrow for A-G
- in a,(c) ; get value
- cp 190 ; A key pressed?
- call z, moveup ; move cursor up
- ; ideally the following keys would be debounced
- ; or whatever, so there was no auto-repeat going on
- ; or at least there was a delay between repeats
- ld bc, 32766 ; keyrow for B-SPACE
- in a,(c) ; get value
- cp 190 ; SPACE key pressed?
- call z, spacehit ; update action
- ld bc, 63486 ; keyrow for 1-5
- in a,(c) ; get value
- cp 190 ; 1 key pressed?
- call z, onehit ; update action
- ld bc, 61438 ; keyrow for 6-0
- in a,(c) ; get value
- cp 190 ; 0 key pressed?
- call z, zerohit ; update action
- ld bc, 49150 ; keyrow for H-ENTER
- in a,(c) ; get value
- push af ; save it
- cp 190 ; ENTER key pressed?
- call z, enterhit ; update action
- pop af ; get it back
- push af ; and save it again
- cp 187 ; K key pressed? (+) symbol
- call z, speedup ; speed up cursor
- pop af ; get action value again
- cp 183 ; J key pressed? (-) symbol
- call z, speeddown ; slow down cursor
- ;
- ; start debug code
- ; ================
- ; debugging - in final routine, we'd loop around
- ; until the action code!=0, at which point we'd RET
- ; to let BASIC handle things. But for now we're just
- ; blindy plotting, printing to the screen and looping forever
- ; until 0 key is pressed
- ;
- _plot ld a, (ypos) ; crappy hack to easily plot the pixel
- ld b, a ;
- ld a, (xpos) ;
- ld c, a ;
- call 8937 ; ROM PLOT - not the entry point, assumes BC setup
- ;
- _print: ld a, 22 ; now print at 0, 0
- rst 16 ;
- ld a, 0 ;
- rst 16 ;
- ld a, 0 ;
- rst 16 ;
- ld bc, (xpos) ; get the xpos value (xpos in C, B is 0)
- call 6683 ; print BC
- ld a, 44 ; and a comma
- rst 16 ;
- ld bc, (ypos) ; get the ypos value (ypos in C, B is 0)
- call 6683 ; print BC
- ld a, 32 ; and print 2 trailing spaces
- rst 16 ;
- ld a, 32 ;
- rst 16 ;
- ld a, 22 ; now, print at 1, 0
- rst 16 ;
- ld a, 1 ;
- rst 16 ;
- ld a, 0 ;
- rst 16 ;
- ld bc, (speed) ; get the speed value (speed in C, B is 0)
- call 6683 ; print BC
- ld a, 32 ; and print a trailing space
- rst 16 ;
- ld a, 22 ; print at 2, 0
- rst 16 ;
- ld a, 2 ;
- rst 16 ;
- ld a, 0 ;
- rst 16 ;
- ld a, (action) ; get the action value
- add a, 48 ; normalise it (0='0', 1='1' etc)
- rst 16 ; print it
- ;
- ld a, (action) ; get the action value
- cp 6 ; if it was 6 (zero pressed)
- ret z ; then we return to basic
- ; otherwise
- halt ; wait for an interrupt
- jp _mainloop ; go back to the top
- ;
- ; end debug code
- ; ==============
- ;
- ;
- ; subroutines
- ; ===========
- ;
- speeddown: ld a, (speed) ; fetch the speed
- dec a ; subtract 1
- jr nz, savespeed ; if this is still >0, we're good to save it
- ret
- speedup: ld a, (speed) ; fetch the speec
- inc a ; add 1
- cp 11 ; we're good as long as its <=10
- jr nz, savespeed ; so save it
- ret
- savespeed: ld (speed), a ; save A back into the speed var
- ld a, 2 ; action code = 2
- ld (action), a ; save action code
- ret
- enterhit: ld a, 3 ; action code = 3
- ld (action), a ; save action code
- ret
- spacehit: ld a, 4 ; action code = 4
- ld (action), a ; save action code
- ret
- onehit: ld a, 5 ; action code = 5
- ld (action), a ; save action code
- ret
- zerohit: ld a, 6 ; action code = 6
- ld (action), a ; save action code
- ret
- moveright: ld a, (xpos) ; fetch the current xpos in A
- ld hl, speed ; get speed address into HL
- ld c, (hl) ; load C with speed
- add a, c ; add C to A
- jr nc, savex ; if it's not overflowed, we're good to save
- ret ; ignore event
- moveleft: ld a, (xpos) ; fetch current xpos in A
- ld hl, speed ; get speed address into HL
- ld c, (hl) ; load C with speed
- sub c ; subtract C from A
- jr nc, savex ; if not underflow, we're good to save
- ret ; ignore event
- moveup: ld a, (ypos) ; get ypos into A
- ld hl, speed ; get speed address in HL
- ld c, (hl) ; get speed in C
- sub c ; subtract C from A
- jr nc, savey ; if no underflow, we're good to save
- ret ; ignore event
- movedown: ld a, (ypos) ; get ypos into A
- ld hl, speed ; and get speed adddress in HL
- ld c, (hl) ; get speed into C
- add a, c ; add C to A
- cp 176 ; compare 176
- jr c, savey ; if A <176 we can save it
- ret ; ignore event
- savey: ld (ypos), a ; save A back into ypos
- jr commoncur ; go and save it etc
- savex: ld (xpos), a ; save A back into xpos
- ; drop thru into commoncur code
- commoncur: ld a, 7 ; action code for cursor move = 7
- ld (action), a ; update action code
- ret
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