Subject: Re: [stella] reading the driving controllers, generic thoughts From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx> Date: Mon, 29 Oct 2001 17:36:45 +0100 |
> This would probably be faster. Don't know how the ROM usage would > compare. What do you guys think? I don't know about this approach, but the way I would read the driving controller would be something like this: RightTable: .byte $02,$00,$03,$01 LeftTable: .byte $01,$03,$00,$02 ReadDC: ; X = player to check (0 or 1) lda SWCHA cpx #$01 beq .Player1 lsr lsr lsr lsr .Player1: and #%00000011 cmp LastDCstate beq .NoDCmovement ldy LastDCstate sta LastDCstate cmp RightTable,y bne .NotRight jmp DoRightTurn .NotRight: cmp LeftTable,y bne .NotLeft jmp DoLeftTurn .NotLeft: .NoDCmovement: > BTW, as Bob Colbert demonstrated, you can read a trackball in trackball > mode on the 2600. I'd be interested to know, however, how fast you can > glide the ball before the 1/60th of a second reads are insufficient. I > would assume that even the Atari trackballs were higher resolution than the > driving controllers, but maybe they are the same. I'll have to dig up my > CX-80 trackball and test this code on one axis to see. It would be > interesting to see Missile Command get modified for trackball mode ;) Reading the trackball only 60 times per second is way too inacurate. You need about 20 reads per frame to get a good control over the cursor. Doing it only once per frame would only result in jerky movement, as you would never be able to read the next value of the code sequence. You just won't be able to move the ball slow enough. (Well I wasn't, so I'm assuming most other people would also have difficulties. ;-) ) I have attatched a little program I was playing around with a while ago. It lets you move a single pixel across the screen with a CX-80 trackball in trackball mode, or a ST mouse, which are compatible. As you can see, reading the mouse/trackball takes quite a lot of processor time during the display and/or a lot of RAM, so it might not be too usefull for most games. Ciao, Eckhard Stolberg
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