Lightgun techdemo

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Lightgun techdemo
by atari2600a on 2007-09-20 (#27097)
Well I thought it necessary to break my previous thread off into a more organized one. I will be updating this post as necessary, & hopefully this game'll turn out to be worth downloading.

ROM & Source: http://mtac.profusehost.net/misc/NES/

Code:
   *=$C000

   !cpu 6502

   !to "gameprg.bin", plain

   sprdma=$00      ;set here do avoid annoying ACME warning



;=============================Init===========================================



reset   CLC         ;clear crap

   LDA #0

   STA scrstat

   

vb1   LDA $2002

   BPL vb1

vb2   LDA $2002

   BPL vb2



   SEI

   LDX #$ff

   TXS

   LDA #0

   STA $2000      ;kill PPU

   STA $2001



   LDA #$20

   LDX #0

   LDY #0

nt1wrt   STA $2006

   STX $2006

   STY $2007

   INX

   CPY #00

   BNE nt1wrt

   CMP #$24

   ADC #1

   BNE nt1wrt



   LDA #$3F

   LDX #$00

   STA $2006

   STX $2006

pal1wrt   LDY bgpal,x

   STY $2007

   INX

   CPX #$20

   BNE pal1wrt

   

   LDX #0

sprwrt   LDA spr1,x

   STA sprdma

   INX

   CPX #4

   BNE sprwrt

   LDA #$00

   STA $4014

   

   

   LDA #%10001000      ;Enable graphics

   STA $2000

   STA ppu0

   LDA #%00011110

   STA $2001

   STA ppu1

   CLI

   

   

loop   JMP loop





;==========================vblank=======================================



vblank

   INC sprdma+3

   LDA sprdma+3      ;NOTE TO SELF:  Find out why Y cord write

   ;CMP #0         ;is causing sprite to dissapear

   ;BNE scrchk

   ;INC sprdma

   

scrchk   LDA scrstat

   CMP #1

   BEQ blkchk

   CMP #2

   BEQ whtchk



gunchk      

   LDA $4016

   AND #%00010000      ;check for trigger status

   CMP #%00010000

   BEQ shoot



dmaset   LDA $00

   STA $4014

   

noshoot

   RTI



shoot   LDA #%00000110      ;kill PPU

   STA $2001

   INC scrstat

   JMP dmaset

   

blkchk   LDA $4016

   AND #%00001000      ;check for black

   CMP #%00000000

   BNE usuck

   LDA #1         ;Don't increment so trigger can be held

   STA scrstat

   STA sprdma+1

   LDA #%00010110

   STA $2001

   JMP dmaset

   

whtchk   LDA $4016      ;check for white

   AND #%00001000

   CMP #%00001000

   BNE usuck

   INC p1scr

   LDA #0         ;reset scrstat

   STA scrstat

   STA sprdma

   LDA ppu1

   STA $2001

   INC p1scr

   LDA p1scr

   LDX #$24

   LDY #$00

   STX $2006

   STY $2006

   STA $2007

   JMP dmaset

   

usuck   LDA #$20

   LDX #$00      ;write text to upper-left corner

suck1   LDY sucktxt,X

   STA $2006

   STX $2006

   STY $2007

   INX

   CPY "*"

   BNE suck1

   LDA ppu1

   STA $2001

   RTI

   

irq   RTI

   

;==========================Data=========================================



bgpal   !byte $0F,$2A,$2B,$2C,$34,$35,$36,$37

   !byte $38,$39,$3A,$3B,$3C,$3D,$3E,$3F



sprpal   !byte $00,$14,$15,$16,$04,$05,$06,$07

   !byte $08,$09,$0A,$0B,$0C,$0D,$0E,$0F



spr1   !byte %00001000,%00000000,%00000011,%00001000



sucktxt   !text "YOU SUCK*"





;==========================Interrupts===================================



   !align $FFFA, $FFFA, $00

   !word vblank      ;

   !word reset      ;

   !word irq      ;IRQ vector currently set to nothing



;==========================Labels=======================================



ppu0=$0200

ppu1=$0201

scrstat=$0202

p1scr=$0203


Code:
   *=$0000

   !CPU 6502

   !to "gamechr.bin", plain

   ;

   !byte %00000010   ;2222223.

   !byte %00000010   ;2222223.

   !byte %00000010   ;2222223.

   !byte %00000010   ;2222223.

   !byte %00000010   ;2222223.

   !byte %00000010   ;2222223.

   !byte %11111110   ;1111113.

   !byte %00000000   ;........

   ;

   !byte %11111110   ;

   !byte %11111110   ;

   !byte %11111110   ;

   !byte %11111110   ;

   !byte %11111110   ;

   !byte %11111110   ;

   !byte %00000010   ;

   !byte %00000000   ;

   ;

   ;

   !align $0200,$0200,$00

   ;

   ;STOLEN C64 ASCII SET, remember to replace w/ tight-ass custom oldskool compy font

   !byte $00,$00,$00,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 32

   !byte $18,$18,$18,$18,$00,$00,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 33

   !byte $66,$66,$66,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 34

   !byte $66,$66,$FF,$66,$FF,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 35

   !byte $18,$3E,$60,$3C,$06,$7C,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 36

   !byte $62,$66,$0C,$18,$30,$66,$46,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 37

   !byte $3C,$66,$3C,$38,$67,$66,$3F,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 38

   !byte $06,$0C,$18,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 39

   !byte $0C,$18,$30,$30,$30,$18,$0C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 40

   !byte $30,$18,$0C,$0C,$0C,$18,$30,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 41

   !byte $00,$66,$3C,$FF,$3C,$66,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 42

   !byte $00,$18,$18,$7E,$18,$18,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 43

   !byte $00,$00,$00,$00,$00,$18,$18,$30,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 44

   !byte $00,$00,$00,$7E,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 45

   !byte $00,$00,$00,$00,$00,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 46

   !byte $00,$03,$06,$0C,$18,$30,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 47

   !byte $3C,$66,$6E,$76,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 48

   !byte $18,$18,$38,$18,$18,$18,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 49

   !byte $3C,$66,$06,$0C,$30,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 50

   !byte $3C,$66,$06,$1C,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 51

   !byte $06,$0E,$1E,$66,$7F,$06,$06,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 52

   !byte $7E,$60,$7C,$06,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 53

   !byte $3C,$66,$60,$7C,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 54

   !byte $7E,$66,$0C,$18,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 55

   !byte $3C,$66,$66,$3C,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 56

   !byte $3C,$66,$66,$3E,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 57

   !byte $00,$00,$18,$00,$00,$18,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 58

   !byte $00,$00,$18,$00,$00,$18,$18,$30,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 59

   !byte $0E,$18,$30,$60,$30,$18,$0E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 60

   !byte $00,$00,$7E,$00,$7E,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 61

   !byte $70,$18,$0C,$06,$0C,$18,$70,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 62

   !byte $3C,$66,$06,$0C,$18,$00,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 63

   !byte $3C,$66,$6E,$6E,$60,$62,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 64

   !byte $18,$3C,$66,$7E,$66,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 65

   !byte $7C,$66,$66,$7C,$66,$66,$7C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 66

   !byte $3C,$66,$60,$60,$60,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 67

   !byte $78,$6C,$66,$66,$66,$6C,$78,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 68

   !byte $7E,$60,$60,$78,$60,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 69

   !byte $7E,$60,$60,$78,$60,$60,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 70

   !byte $3C,$66,$60,$6E,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 71

   !byte $66,$66,$66,$7E,$66,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 72

   !byte $3C,$18,$18,$18,$18,$18,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 73

   !byte $1E,$0C,$0C,$0C,$0C,$6C,$38,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 74

   !byte $66,$6C,$78,$70,$78,$6C,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 75

   !byte $60,$60,$60,$60,$60,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 76

   !byte $63,$77,$7F,$6B,$63,$63,$63,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 77

   !byte $66,$76,$7E,$7E,$6E,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 78

   !byte $3C,$66,$66,$66,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 79

   !byte $7C,$66,$66,$7C,$60,$60,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 80

   !byte $3C,$66,$66,$66,$66,$3C,$0E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 81

   !byte $7C,$66,$66,$7C,$78,$6C,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 82

   !byte $3C,$66,$60,$3C,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 83

   !byte $7E,$18,$18,$18,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 84

   !byte $66,$66,$66,$66,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 85

   !byte $66,$66,$66,$66,$66,$3C,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 86

   !byte $63,$63,$63,$6B,$7F,$77,$63,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 87

   !byte $66,$66,$3C,$18,$3C,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 88

   !byte $66,$66,$66,$3C,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 89

   !byte $7E,$06,$0C,$18,$30,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 90

   !byte $3C,$30,$30,$30,$30,$30,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 91

   !byte $0C,$12,$30,$7C,$30,$62,$FC,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 92

   !byte $3C,$0C,$0C,$0C,$0C,$0C,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 93

   !byte $00,$18,$3C,$7E,$18,$18,$18,$18,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 94

   !byte $00,$10,$30,$7F,$7F,$30,$10,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 95

   ;

   ;

   ;

   !align $1000, $1000, $00

   ;

   ;

   !byte %00000000   ;........

   !byte %00011000   ;...33...

   !byte %00111100   ;..3331..

   !byte %01110010   ;.333221.

   !byte %01100010   ;.332221.

   !byte %00000100   ;..2221..

   !byte %00011000   ;...11...

   !byte %00000000   ;........

   ;

   !byte %00000000   ;

   !byte %00011000   ;

   !byte %00111000   ;

   !byte %01111100   ;

   !byte %01111100   ;

   !byte %00111000   ;

   !byte %00000000   ;

   !byte %00000000   ;

   ;

   !byte %11111111   ;33333333

   !byte %11111111   ;33333333

   !byte %11111111   ;33333333

   !byte %11111111   ;33333333

   !byte %11111111   ;33333333

   !byte %11111111 ;33333333

   !byte %11111111   ;33333333

   !byte %11111111   ;33333333

   ;

   !byte %11111111

   !byte %11111111

   !byte %11111111

   !byte %11111111

   !byte %11111111

   !byte %11111111

   !byte %11111111

   

   





   ;

   !align $2000,$2000, $00

   !eof


Code:
   *=$000000

   !to "techdemo.nes", plain

   

   ;====================iNES Header Begin====================

   

   ; iNES identifier

   

   !text "NES"

   !byte $1A

   

   ; Number of PRG-ROM blocks

   

   !byte $01

   

   ;

   ; Number of CHR-ROM blocks

   

   !byte $01

   

   ;   

   ; ROM control bytes: Horizontal mirroring, no SRAM

   ; or trainer, Mapper #0

   

   !byte %00000000, %00000000

   

   ;

   ; Filler

   

   !byte $00,$00,$00,$00,$00,$00,$00,$00

   

   ;====================iNES Header End======================

   ;

   ;=====================Program Start=======================

   !bin "gameprg.bin"

   !bin "gamechr.bin"

   !eof

by atari2600a on 2007-09-20 (#27098)
Anyways, I can't get the screen to turn black on the trigger being pulled, under the 'shoot' label. (Also I've noticed the Nesdevwiki info on the Zapper conflicts w/ the nestech.txt info) Can anybody see why?

Oh, & I know the sprite isn't moving. I'm still tweaking that code, & I can't really fix it on this computer right now as it's runing Ubuntu linux & I'd have to run Wine to compile each time for each file, w/o the BAT file I have set up.

by atari2600a on 2007-09-24 (#27204)
Right now I'm stuck on getting the screen to blank on the shoot routine. I'm reading the trigger fine now but for some reason somewhere along the line writing #0 to $2001 isn't clearing the screen. Should I use a bitwise instruction on it (& by it, I mean the buffer in memory I'm using) instead?

by tepples on 2007-09-25 (#27209)
atari2600a wrote:
but for some reason somewhere along the line writing #0 to $2001 isn't clearing the screen.

Clearing CPU $2001 to 0 fills the screen with the color in palette entry 0. Do you also set palette entry 0 (PPU $3F00) to #$0F?

by atari2600a on 2007-09-25 (#27226)
tepples wrote:
atari2600a wrote:
but for some reason somewhere along the line writing #0 to $2001 isn't clearing the screen.

Clearing CPU $2001 to 0 fills the screen with the color in palette entry 0. Do you also set palette entry 0 (PPU $3F00) to #$0F?


So THAT'S what bg palette #0 does! Damn I really wish the NES was as well documented as 6502 computers!:P

Well anyways I'm getting this odd scrolling effect. The effect is *completely* unintentional, but the effect looks awesome nonetheless. I should *really* start uploading my *.NES ROM to one of my servers...

by Disch on 2007-09-26 (#27231)
The address you set with $2006 is the same address that the PPU uses for its scrolling. So whenever you draw stuff to $2007, you're unintentionally mucking up the scroll. Therefore, in VBlank, after you're done drawing, you should always reset the scroll with a write to $2000 (to set the NT bits) and dual writes to $2005 (to set the X,Y scroll). Once you set the scroll in that manner, do not mess with $2006 or $2007 any more or else the scroll will get mucked up again

by atari2600a on 2007-09-26 (#27235)
Hmm...that would *kinda* explain it. The $2006/$2007 code in usuck was put there when it started acting up, but it shouldn't even be executed unless the trigger was pulled away from the screen or an IRQ was executed...I'll have to look more into this...

by Disch on 2007-09-26 (#27236)
Something else it might be:

If you turn the PPU on too late (after rendering has started), you'll miss the scroll reset (which the PPU does at the start of the frame -- but only if the PPU is on). If you're turning off the PPU during VBlank, be sure you're turning it back on before VBlank is over (or don't turn it off at all -- you don't need to have the PPU off if you finish all your drawing in VBlank)

by tokumaru on 2007-09-26 (#27237)
Disch wrote:
If you're turning off the PPU during VBlank, be sure you're turning it back on before VBlank is over (or don't turn it off at all -- you don't need to have the PPU off if you finish all your drawing in VBlank)

IMO, "good" VBlank code should always end before VBlank is over. If it doesn't, turning the PPU off or not, you get visual glitches. Sure, the effects are much worse when the PPU is on, because not only you'll get currupt graphics for that frame, but you may end up corrupting the name tables and so on, affecting future frames. If you have rendering off, when you turn it back on the screen will just be misplaced, and the image will appear to "jump" because of that one frame.

Anyway, always do your best to keep your VBlank code within VBlank time. If you need more than that time, you'll either have to turn rendering off early, or turn it on late, but always at the same time, by means of IRQ's, sprite 0 hits or timed code, so that the image does not "jump".

by atari2600a on 2007-10-23 (#27789)
Wow, it's been a while since I last updated this thread! :P

Anyways, now it just stalls somewhere after blkchk, & I can't seem to find out why...can anyone help me on this?

Also added link to ROM to first post...