[stella] Obviously doing something wrong...

Subject: [stella] Obviously doing something wrong...
From: "Ruffin Bailey" <rufbo@xxxxxxxxxxxxx>
Date: Sun, 24 Sep 2000 14:55:19 -0400
Welp, I've dug out my demo from two years ago (thanks again to Eckhard for
fixing a few bugs), but all I had was Eckhard's dissembly of my bin from the
archive so I've started in over-commenting again.  Hoping to have a _very_
simple example of reading the joystick as an obvious next step to Nick's

Anyhow, as things stand, Player Zero is ALWAYS moving right unless I move
the stick to the left-- with nothing different if I move the stick to the
right.  I tried commenting out where I check for the right movement, and
sure enough the movement stops.  Isn't d7 the bit read by BMI & BPL?  I'll
quote the part of the code where I read the joystick, and include the whole
shibang as an attachment.  Mind you, I'm still hacking, so comments about
how the player's going to disappear when he's on the same scan as the
beginning of the platform in the PF is a bit premature.  ;^)  Just trying to
figure out what bone-headed mistake I made with the joystick reads.

Sorry in advance if this is some silly error that I woulda gotten with a
little more patience...  gotta run off to work to get ahead a few hours so I
decided it was time to stop with the demo practice.


Ruffin Bailey

PS  Any particular reason that Thrust is $25 and not the usual $16 at Hozer?
Any supercool docs or something?  ;^)

Here's the "crucial" code:

; reset hmove with y for testing (remove later) (I already reset with A
 ldy #$00
 sty HMP0
       BMI    LF06C   ; if there's a zero in a bit, then we know that
someone closed the switch with the joystick
   ; therefore, if there's a one, then the switch is still open.  BMI is
"Branch on Minus", which is
   ; defined as having bit 7 set as 1.  So if we have a minus, we don't have
a zero in d7 of swcha
   ; and shouldn't make the fellow move to the right.  Jump over the next
two lines.
   ; A plus (d7 = 0) means set the hmp0 to move the dude to the right.

       LDY    #$F0    ; least amount of movement to the right
       STY    HMP0    ; shove it into HMOVE for player zero
LF06C: ROL            ; This rolls the bits to the left.  The carry flag
gets whatever was in d7, d7 gets whatever was in d6, etc
   ; I can't remember if the acum's d0 gets what was in the carry flag right
off the top of my head.

Attachment: joy.das
Description: Binary data

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