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For about a month I have been studying a little bit of Assembly through the great material gathered on the Random Terrain website. (https://www.randomterrain.com/atari-2600-memories.html#assembly_language) Although I managed to create my own kernel, several parts of it I still don't understand. And instead of spending effort with such deep learning, I researched if it was possible to simply create a kernel for batariBasic and continue programming in bB. I found this post which presents a way to use a custom kernel. With some modifications I got to this version below. It's a 2LK and I'm trying to use the same variables as bB to control the players, but this is the problem: I can't (I don't have enough knowledge) use the players pointer correctly. Could anyone clarify my ideas? Player0Draw = $A4 ; I'm not using the vars (0-47) Player1Draw = $A5 BackgroundPtr = $A6 ; $A7 .customdrawscreen custom_eat_overscan ;bB code runs during overscan. We wait for overscan to finish so the ;frame timing doesn't get screwed up. lda INTIM bmi custom_eat_overscan custom_do_vertical_sync ;just a standard vsync lda #2 sta WSYNC ;one line with VSYNC sta VSYNC ;enable VSYNC sta WSYNC ;one line with VSYNC sta WSYNC ;one line with VSYNC lda #0 sta WSYNC ;one line with VSYNC sta VSYNC ;turn off VSYNC custom_setup_vblank_timing ;use bB timing variables so it should work with both PAL and NTSC ifnconst vblank_time lda #42+128 else lda #vblank_time+128 endif sta TIM64T ; feel free to throw useful pre-kernel code in here, so long as it ; completes before vblank is over. custom_eat_vblank ;wait for vblank to complete lda INTIM bmi custom_eat_vblank lda #0 sta WSYNC sta VBLANK custom_setup_visible_timing ;my preference is to use TIM64T to ensure a full screen is drawn. lda #230 sta TIM64T ;------------------------------------------------------------------------------ ; Desenha a parte superior da tela ; 192 - 22 scanlines = 192 - (11*2) = 170 lda #$02 ; Cor cinza no PF sta COLUPF ; COR no PF lda #1 ; sta CTRLPF ; Liga o REFLECT ldx #11 UpperSection: sta WSYNC lda customPFPattern,x sta PF0 sta PF1 sta PF2 lda customPFColor,x sta COLUBK sta WSYNC dex bne UpperSection stx PF0 stx PF1 stx PF2 ; y position lda #80 adc player0height sbc player0y sta Player0Draw ;------------------------------------------------------------------------------ ;-- AREA DE JOGO ;------------------------------------------------------------------------------ ; Desenha a área de jogo ; 170 - 160 scanlines = 170 - (80*2) = 10 (base ... not implemented) ldy #80 ; Carrega o y com o tamanho da área de jogo KernelLoop: ; 15 - todal de 15 ciclos, vindos do bne KernelLoop ; Continuação da segunda linha do 2LK ; precalcula os dados usados na primeiralinha do 2LK lda player0height ; 2 17 - altura do Player0 - IMPORTANTE!! este valor deve ser altura-1 dcp Player0Draw ; 5 22 - Decrementa Player0Draw e compara com a altura bcs DoDrawGrp0 ; 2 24 - (3 25) se o Carry estiver setado, player0 está na scanline atual lda #0 ; 2 27 - caso contrário, desliga o player0 .byte $2C ; 4 31 - $2C = BIT with absolute addressing, trick that ; causes the lda (HumanPtr),y to be skipped DoDrawGrp0: ; 25 - 25 ciclos do pior caso na linha bcs DoDrawGrp0 lda (player0pointer),y ; 5 30 - carrega o formato do player0 <<----------------------------- It's not working sta WSYNC ; 3 33 - Aguarda o fim da scanline ;------------------------------------------------- ; começo da primeira linha do 2LK sta GRP0 ; 3 3 - @ 0-22, desenha o player0 efetivamente (entre os ciclos 0 e 22) lda (BackgroundPtr),y ; 5 8 - Atualizo a linha do BG sta COLUBK ; 3 11 - guardo o valor do BG no resitrador COLUPF lda (player0color),y ; 5 16 - Pega a cor do Player0 sta COLUP0 ; 3 19 - seta a cor do Player0 ; todo esse código acima precisa estar entre o ciclo 0 e 22 ; para adicionar mais alguma coisa neste scanline, é preciso liberar algo acima ; sobraram apenas 3 ciclos ... é possível ainda colocar algum padrão de PF em PF1 e PF2 ;-------------------------------------------------- ; pre calcula os dados necessáriso para a segunda linha do 2LK ; lda player1height ; 2 21 - altura do Player0 - IMPORTANTE!! este valor deve ser altura-1 ; dcp player1y ; 5 26 - Decrementa Player1Draw e compara com a altura ; bcs DoDrawGrp1 ; 2 28 - (3 18) se o Carry estiver setado, player1 está na scanline atual ; lda #0 ; 2 31 - caso contrário, use 0 para desligar o player1 ; .byte $2C ; 4 35 - $2C = BIT with absolute addressing, trick that ; causes the lda (BoxPtr),y to be skipped DoDrawGrp1: ; 28 - 28 ciclos vindo do bcs DoDrawGRP1 ; lda (player1pointer),y ; 5 32 - Carrega a aparencia do player1 sta WSYNC ; 3 35 - Aguarda o inicio de uma nova scanline ;--------------------------------------- ; inicio da segunda linha do 2LK ; sta GRP1 ; 3 3 - @0-22, desenha o player1 efetivamente (entre os ciclos 0 e 22) ; lda (player1color),y ; 5 8 - Pega a cor do Player1 ; sta COLUP1 ; 3 11 - seta a cor do Player1 ; todo o codigo acima precisa estar entre os ciclos 0 e 22. ; ainda há 11 ciclos sobrando, talvez um playfield ou ball, ou missile ; possa entrar aqui neste ponto. dey ; 2 13 - decrementa o y bne KernelLoop ; 2 15 - se não for igual a zero, pula plá pra cima ;------------------------------------------------------------------------------ ;------------------------------------------------------------------------------ ;------------------------------------------------------------------------------ sty COLUBK custom_eat_visible ;wait for the visible display to complete lda INTIM bne custom_eat_visible custom_setup_overscan_timing ifnconst overscan_time lda #35+128 else lda #overscan_time+128-3-1 endif sta TIM64T lda #%11000010 sta WSYNC sta VBLANK ;bB macro to return from a bank-switch gosub or from a regular gosub. RETURN customPFPattern .byte %11011001 .byte %11111111 .byte %11011001 .byte %11001001 .byte %11011111 .byte %11011001 .byte %11011001 .byte %11001001 .byte %01001001 .byte %01001001 .byte %01001001 .byte %01001001 .byte %11001001 .byte %00001000 .byte %00001000 .byte %11001001 .byte %11011001 customPFColor: .byte $00, $AA, $00, $AA, $00, $AA, $00, $AA, $00, $AA, $00, $AA, $00 Thanks in advance.

(STANDARD KERNEL - NOT DPC+) When using both playercolor kernels with the playfield colors kernel, RT's Batari page says there is a known issue with a stairstep/rolling lines effect on the left side of the screen. Is there any workaround to this? Some bit of code to be inserted however sloppy that could eliminate this? I am not trying to learn how to write another kernel right now. Also; Can any of those kernels run in VBLANK? Would it help?