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dsv101 · Post by **dsv101** » Tue Jun 28, 2011 10:58 pm

ok cool, i think i got this

dsv101 · Post by **dsv101** » Tue Jun 28, 2011 11:27 pm

since a byte = 8 bits, how do i access each individual bit if i want to?

Post by **Memblers** » Tue Jun 28, 2011 11:54 pm

In short, you use AND to clear bits, ORA to set bits, and EOR to invert bits.

You can also use ASL/LSR/ROL/ROR to move a bit into the carry flag and check the carry flag (BCC/BCS), and using BPL/BMI is a common trick to check the state of the highest bit (even without any other operation, after an LDA is fine, such as you see with the common LDA $2002 / BPL loop)

dsv101 · Post by **dsv101** » Wed Jun 29, 2011 12:06 am

ok man

dsv101 · Post by **dsv101** » Sat Jul 16, 2011 9:22 pm

Some sprites wont show, and i dont see why.
The second set of 6 wont show, is my compiler screwing up, or am I an idiot?

Code: Select all

sprites:                    ; y tile atr x

  .db $10, $00, $01, $10    ; $0200-$0203 Ship left half
  .db $10, $01, $01, $18    ; $0204-$0207 Shtp Second Half

  .db $10, $03, $01, $20    ; $0208-$020B Bullet
  .db $10, $03, $01, $28    ; $020C-$020F Bullet
  .db $10, $03, $01, $30    ; $0210-$0213 Bullet
  .db $10, $02, $01, $38    ; $0214-$0217 Bullet
  .db $10, $02, $01, $40    ; $0218-$021B Bullet
  .db $10, $02, $01, $48    ; $021C-$021F Bullet

  .db $20, $03, $01, $20    ; $0220-$0223 Bullet
  .db $20, $03, $01, $28    ; $0224-$0227 Bullet
  .db $20, $03, $01, $30    ; $0228-$022B Bullet
  .db $20, $02, $01, $38    ; $022C-$022F Bullet
  .db $20, $02, $01, $40    ; $0230-$0233 Bullet
  .db $20, $02, $01, $48    ; $0234-$0237 Bullet

cpow · Post by **cpow** » Sat Jul 16, 2011 9:28 pm

dsv101 wrote:Some sprites wont show, and i dont see why.
The second set of 6 wont show, is my compiler screwing up, or am I an idiot?

The data looks OK to me, how about pasting the code that's putting it in RAM and DMAing (or copying via $2003/$2004 perhaps) it to the PPU?

thefox · Post by **thefox** » Sat Jul 16, 2011 10:08 pm

Open the ROM in Nintendulator (or some other debugger with PPU viewer) and see if the sprites appear in the sprite list. If not, single step through your code to find out why.

3gengames · Post by **3gengames** » Sat Jul 16, 2011 10:16 pm

Are you enabling rendering, loading the palettes, and such?

dsv101 · Post by **dsv101** » Sun Jul 17, 2011 1:08 pm

Code: Select all

LoadPalettes:
  LDA $2002
  LDA #$3F
  STA $2006
  LDA #$00
  STA $2006
  LDX #$00
LoadPalettesLoop:
  LDA palette, x
  STA $2007
  INX
  CPX #$20
  BNE LoadPalettesLoop



LoadSprites:
  LDX #$00
LoadSpritesLoop:
  LDA sprites, x
  STA $0200, x
  INX
  CPX #$20
  BNE LoadSpritesLoop

  LDA #%10000000
  STA $2000

  LDA #%00010000
  STA $2001

3gengames · Post by **3gengames** » Sun Jul 17, 2011 1:13 pm

Are the sprites in the 1st graphics table? Other than that, looks perfectly fine to me.

cpow · Post by **cpow** » Sun Jul 17, 2011 1:24 pm

Where's the:

Code: Select all

   lda #2
   sta $4014

There's only code there to set up the sprite RAM area. Not that that is the problem...it's just hard to tell what might be wrong with only snippets.

EDIT: Nevermind in this case the problem is obvious after looking again:

Code: Select all

LoadSpritesLoop:
  LDA sprites, x
  STA $0200, x
  INX
  CPX #$20
  BNE LoadSpritesLoop

You have way more than 32 bytes of sprite data...so you're cutting off the copy loop too early.

qbradq · Post by **qbradq** » Sun Jul 17, 2011 1:26 pm

Do you see the "cpx #$20" line? That controls how many bytes you are loading into your sprite RAM. $20 is 32 in decimal, or 8 sprite's worth of data. You have 56 bytes of data for 14 sprites. So change the "cpx #$20" to "cpx #56" and it should all work.

Each time you add or remove sprites from that table you'll need to change that line. Sounds like a great use for an EQU statment.

Example:

Code: Select all

.equ sprite_data_length 56
; 56 bytes of sprite data

; ...In your loading loop...
cpx #sprite_data_length

That way you'll only have to change the EQU line and not have to go hunting through your code.

Got ninja'ed, but yea

3gengames · Post by **3gengames** » Sun Jul 17, 2011 1:31 pm

Damn, didn't think that was the problem. Sorry dude. But anyway, CPX compares X to a number, you go that right? When the INX and it ups it by 1, you compare to find the end. That makes sense right?

dsv101 · Post by **dsv101** » Sun Jul 17, 2011 3:53 pm

yes 3gen, i know what that does. I didnt cacy that #$20 in there like i should have, thanks guys.

3gengames · Post by **3gengames** » Sun Jul 17, 2011 5:09 pm

Okay, just wanted to make sure you understood that. Is it working now okay?

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Some sprites wont show

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