Slow Down Player Movement

[lerugray]

Hello all, I'm currently teaching myself how to program the 2600 using the 8bit workshop tutorials. Currently, I am wondering how to slow down player movement. Here is the code I am currently using for player movement.

 

; Read joystick movement and apply to object 0
MoveJoystick
; Move vertically
; (up and down are actually reversed since ypos starts at bottom)
	ldx YPos
	lda #%00100000	;Up?
	bit SWCHA
	bne SkipMoveUp
        cpx #2
        bcc SkipMoveUp
        dex
SkipMoveUp
	lda #%00010000	;Down?
	bit SWCHA 
	bne SkipMoveDown
        cpx #183
        bcs SkipMoveDown
        inx
SkipMoveDown
	stx YPos
; Move horizontally
        ldx XPos
	lda #%01000000	;Left?
	bit SWCHA
	bne SkipMoveLeft
        cpx #16
        bcc SkipMoveLeft
        dex
SkipMoveLeft
	lda #%10000000	;Right?
	bit SWCHA 
	bne SkipMoveRight
        cpx #153
        bcs SkipMoveRight
        inx
SkipMoveRight
	stx XPos
	rts

Normally, I am used to coding for the NES and I would be able to just DEX and NOP until the player slowed down, wondering what I would do here in this instance. Thank you!

 

 

And here is a link to my current test project, took me all day yesterday how to figure out the 'ground' bit of playfield 2600 Test

Edited February 18, 2021 by lerugray

[Thomas Jentzsch]

There are at least two methods:

1. In case you have a frame counter, execute MoveJoystick only every 2nd frame.
2. Use fractional numbers. For that you need a sum variable and a constant added to it each frame. Only call MoveJoystick when the sum variable wraps around.

The latter is more flexible as you can fine tune the speed very gradually.

[lerugray]

10 minutes ago, Thomas Jentzsch said:

There are at least two methods:

1. In case you have a frame counter, execute MoveJoystick only every 2nd frame.
2. Use fractional numbers. For that you need a sum variable and a constant added to it each frame. Only call MoveJoystick when the sum variable wraps around.

The latter is more flexible as you can fine tune the speed very gradually.

Thank you Thomas!

 

I think I can visualize your first example, but would you mind providing a short example of your second please?

[Thomas Jentzsch]

Sure.

  lda moveSum
  clc
  adc #SPEED      ; e.g. 128 for 50% or 192 for 75% speed
  sta moveSum
  bcc .skipMove
  jsr MoveJoystick
.skipMove

 

[lerugray]

On 2/18/2021 at 8:55 AM, Thomas Jentzsch said:

Sure.

  lda moveSum
  clc
  adc #SPEED      ; e.g. 128 for 50% or 192 for 75% speed
  sta moveSum
  bcc .skipMove
  jsr MoveJoystick
.skipMove

 

Not sure if I am doing this incorrectly but I can't seem to get it to work on my end

MoveSpeed
	lda MoveSum
	clc
        adc #128
        sta MoveSum
        bcc MoveSpeed
        jsr MoveJoystick

 

Adversary(1).a

[Thomas Jentzsch]

You are branching to "MoveSpeed", but you should branch after "jsr MoveJoystick"

[lerugray]

2 minutes ago, Thomas Jentzsch said:

You are branching to "MoveSpeed", but you should branch after "jsr MoveJoystick"

Thank you for your patience with me, I think I'm still getting confused though as to what you mean. where should I be branching to after jsr MoveJoystick if not MoveSpeed to use it as a counter?

 

MoveSpeed
	lda MoveSum
	clc
        adc #128
        sta MoveSum
        jsr MoveJoystick
        bcc MoveSpeed

 

[Thomas Jentzsch]

  bcc .skipMove
  jsr MoveJoystick
.skipMove

This is the correct code in question again. Hope it helps.

[lerugray]

5 minutes ago, Thomas Jentzsch said:

  bcc .skipMove
  jsr MoveJoystick
.skipMove

This is the correct code in question again. Hope it helps.

This worked! Dont know what I was thinking, thanks!

[DEBRO]

Hi there,

On 2/18/2021 at 8:04 AM, lerugray said:

Hello all, I'm currently teaching myself how to program the 2600 using the 8bit workshop tutorials. Currently, I am wondering how to slow down player movement.

If the true intent is to control the player movement then you should move this code into the joystick routine where you are moving the player. In its current position you are controlling when to poll for the joystick input instead.

[lerugray]

On 2/21/2021 at 3:35 PM, DEBRO said:

Hi there,

If the true intent is to control the player movement then you should move this code into the joystick routine where you are moving the player. In its current position you are controlling when to poll for the joystick input instead.

Doesn't it get caught in an endless loop though given it jumps right back to the Joystick routine? Thanks for your help