I'm trying to compress my code for loading/moving paddle sprites. I'm using 6 tiles for each paddle.
In my code to move the paddles, I've made it so I run a subroutine to take care of the middle paddle sprites.
I'm using a 4 byte variable for the middle sprites, I have 2 separate variables for the top and bottom sprites which I use for collision detection with the border.
This is my current move paddle up code:

MovePaddleUp:
    LDX #$00
;;if up button pressed
    LDA buttons1 ; 3rd bit is up. Don't care about other bits.
    AND #%00001000 ; if it isn't pressed the zero flag is set so we skip.
    BEQ MovePaddleUpDone ; Up button wasn't pressed skip code.
TopPaddle
    LDA paddle1ytop
    SEC
    SBC #$01
    STA paddle1ytop

    JSR UpPaddleNext ; jump to subroutine for the inbetween paddles.

    LDA paddle1ybot
    SEC
    SBC #$01
    STA paddle1ybot
BottomPaddle
;; if paddle top > top wall
;; move paddle top and bottom up
MovePaddleUpDone:

Here is the subroutine:
    LDX #$00
UpPaddleNext:
    LDA paddle1ynext,x
    SEC
    SBC #$01
    STA paddle1ynext,x
    INX ; go to next byte in paddle1ynext?
    CPX $03
    BNE UpPaddleNext
RTS
I think the problem lies in my subroutine or my initialising of variables which is below, is it possible to access the next byte of memory stored in my variable with the above syntax?

I initialise the variables in the 4 byte variable as follows:

  LDA #$68
  STA paddle1ynext

  LDA #$70
  STA paddle1ynext+1

  LDA #$78
  STA paddle1ynext+2

  LDA #$80
  STA paddle1ynext+3

Is that correct syntax? I thought I've seen it somewhere.

Basically what is happening on screen is that some of the paddle sprite appears at the top and bottom of the screen, not a full tile just a small section. Then it goes completely offscreen, then the full paddle comes together for a second and I can move it together as I intend. But if I keep moving it up the top sprite of the paddle goes above all the rest creating a gap. Could this be related to Vblank time?

A few things: What are "TopPaddle" and "BottomPaddle"? Variables, labels? Nothing seems to be happening with them, no reference elsewhere. Maybe I don't know of an alternate syntax for what you use them for because I would think those would throw compiler errors.

Secondly, I assume you have a block of code that takes the values stored in paddle1ytop, paddle1ybot, paddle1ynext, +1, +2, +3 and then puts them into the sprite memory (i.e. at $0204, $0208, etc.) otherwise changing these variables wouldn't be helping change what is on the screen.

Lastly, and I think this is the issue - LDX #$00 should come after the UpPaddleNext: label in your subroutine. Otherwise it never clears the X register out because the JSR goes right to the label, and whatever happens to be in X is whatever you use as your starting index from there onward. I think that is what is causing the weird behavior.

Dan

There's something very wrong with your sprites page writes it looks like, look at it in the hex editor. Good luck finding it.

Should it be CPX #$03 and not CPX $03?

Good call KHAN. Also I was wrong about the LDX comment. It does need to be cleared before looping but shouldn't be under the label you have. Rather you should be jumping to a label above the LDX #$00 instruction, then once the loop is started you loop to the label you currently have in your code.

You guys are so awesome

TopPaddle and BottomPaddle were just old labels I had, I've gotten rid of them now.

I update all the sprites elsewhere in my code, exactly how you mentioned.

Good point about LDX, I'm lucky that works because X is put to #$00 before I enter that subroutine, so the way I wrote it above the label serves no purpose as you mentioned. I'll make another label there for more defensive programming, thanks for pointing that out.

Changing the compare fixed it straight away!, awesome spot! I've been caught out with that before, I'll be much more careful in the future. Thanks again guys!

go glenn gooo! Make awesome pong and then....something even more awesome!

Hmm, now I have a collision issue,I'm certain this time it's just a syntax thing. Am I using CMP correctly with variables? I'm sure my logic is right, because if ballx < paddle1x in my first check, the code executes as I want.

CheckPaddleCollision:
  ;;if ball x < paddle1x
  LDA ballx   
  CMP #PADDLE1X
  BCS CheckPaddleCollisionDone ; PADDLE1X=PADDLE1X-ballx, if ballx
  ;;if bally > paddleytop
  LDA bally
  CMP #paddle1ytop
  BCC CheckPaddleCollisionDone ; paddle1ytop=paddle1ytop-bally, if bally>paddletop then carry so execute code. If bally
  ;;if bally < paddleybot
  LDA bally
  CMP #paddle1ybot            
  BCS CheckPaddleCollisionDone ; paddleybot=paddleybot-bally, if bally
  ;;Bounce ball now.
  LDA #$01
  STA ballright             ; ball now moves right on next NMI.
  LDA #$00
  STA ballleft         ;;bounce, ball now moving right
CheckPaddleCollisionDone:

*EDIT*
I think I've got my subtracts around the wrong way in my comments, CMP performs a SUB the same way except it isn't stored in memory, I've thought of it back-to-front that may be the problem.

*EDIT*
Fixed!! That damn CMP got me again! I should be using CMP "varname" not CMP # "varname"

Remove the # sign and you'll be all set. It will substitute the value at that memory address for the variable, not the address of the variable itself.

Your exactly right muffins, I just realised that around a minute ago!

Sup all just want to say first that those tutorials are amazing!! thanks alot!

Now i have a couple of questions so far..

1. How can you clear the sprites?? when i come back to the title screen after any players have 15 points, the sprites are still on the screen with the title screen since i only updated the title background...

2. Now when players have 15 points, i enter the gameover state in which i just stop moving the sprites and wait for a player the press A, and in the title screen waiting to press START. The problem is if i put both Gameover and Title state to press Start.. even if you press quickly (lol) it will pass both state.. is there a way to keep START button for both screen but not passing over the title screen. Something like making sur the buttons are unpressed before you pressed START again.

Thanks!

Question 1: Use 2 kinds of game states, one for the logic in the infinite loop, and one for the NMI, say you call them TitleLogic/TitleNMI, PlayingLogic/PlayingNMI e.t.c.
Then you just don't transfer the sprites with DMA in the game states you don't want sprites in.

Question 2: http://www.nintendoage.com/forum/...
Nothing about it in the tutorial, but look in the source code how he handle input there.

1:
LDX #$00
Loop:
LDA #$FF
STA $0300,x (or wherever your sprites are)
INX
CPX #$FF (or however many sprites you're using)
BNE Loop
RTS

2. Just create a flag in the zero page and set it to 1 when a button is pressed. If the flag is still 1, skip the controller reading routine. When you release the button, set the flag to 0.

1: if i understand well... putting the four settings of a sprites at $0200, x to $FF will "clear/delete" the sprites?

2: i havent looked yet at the code but i will soon.
Even with a fully working pong i dont know what is a flag :S

ty for quick reply

Yes.  Actually, technically you only need to set the sprites' Y coordinate values to a high value so they will be offscreen.  But it's common to write #$FE or whatever to all sprite attributes because it's not worth the trouble to isolate every 4th index.

ohhh great to know!!

and i have looked at the code for the joypad and basicly you just skip the instruction if you are pressing the same button as the previous frame.

Ive got an other question!
Let's say i want to make a game with a gun, the gun would shoot 1 bullet (sprite) every half second if i hold the A button... how do i do that?
I've read that their is 60 frame per second so basicly it reads the code 60 times per second??
So could i do a counter and just fire everytime the counter hit 30 then reset the count blablabla.
Or am I completly misunderstanding the situation here lol

No, you're right on.

;;A Held? JSR Routine

Routine:
LDA Timer
CMP #$30
BCS .Shoot
INC Timer
RTS
.Shoot:
;;shoot code
LDA #$00
STA Timer
RTS

it was inevitable but here I am asking for help again. I'm trying to map my controller to move sprites for the paddles. I can get a sprite to move but with the wrong button.
MovePaddleUp:
LDA buttons1
AND #$00001000 <--------- this is supposed to be the up button but NESASM throws an error at me when I do this
BEQ MovePaddleUpDone ; but if I change it to #$00000010, or #$00000001 it works but with start
LDA $0204 ; and right respectively is there something else I need to do to get this to work correctly before hand?
SEC
SBC #$01 ; if up button pressed
CMP #TOPWALL
STA $0204 ; if paddle top > top wall ; move paddle top and bottom up

-----EDIT----

figured it out  #$00001000 is supposed to be #%00001000. got the $ and the % mixed up.

After a game over the game shortly plays and crashes. I can't get the collision date to work either.

http://pastebin.com/5X1Us01D...

Help please.

It would really help if you provided a ROM just so we could see what is going on rather than trying to figure out what "after a game over the game shortly plays and crashes" means.

Ok

http://depositfiles.com/files/7gv...

Another person caught the freezing problem. The Nmi was filling up the stack. New code:

http://pastebin.com/uL1vFmDL
The collision data fails to work I can't figure out why :/.The code to make the ball bounce seems to work.

I suck at fixing other people's code. Typically it doesn't work because you mess up a BCS or BCC. Like get them backwards. It helps to draw it out.

If NMI fills up the stack, you have an open JSR/RTS loop somewhere.

One thing that's jumping out at me is at the end of your gamestates, you're doing a JMP straight back to your GameEngine, where you should be doing a JMP to GameEngineDone. I don't think your code is even getting to any of your other subroutines.

I got a JMP GameEngineDone at the end of EnginePlaying.

The code:

CheckPaddleCollision:
LDA ballx
CMP #PADDLE1X+8
BCS CheckPaddleCollisionDone ;;if ball x > left wall, still on screen, skip next section
LDA bally
CMP paddle1y+2
BCS CheckPaddleCollisionDone ;;if ball y > top wall, still on screen, skip next section
LDA bally
CMP paddle1y2+2
BCC CheckPaddleCollisionDone ;;if ball y < bottom wall, still on screen, skip next section
LDA #$01
STA ballright
LDA #$00
STA ballleft ;;bounce, ball now moving right
JMP CheckPaddleCollisionDone
CheckPaddleCollisionDone:
RTS

Seems right to me.

Finished:

http://pastebin.com/cZAUUTfH
Any tips for optimization?

I'm at a loss... I need to display a number using a background tile on the title screen... but graphics are only uploaded to the PPU memory once on the init code (before the JMP Forever loop). Can someone help me? Do I need to reupload BG data frame-by-frame?

Edit: ooh never mind, didn't notice that you could set the PPU writing address to anywhere you wanted to. Cool