[stella] Auto detecting paddles in port 1 or port 2

[Dennis Debro]

Hi there,

I know this is an old thread (almost a year now) but I found this recently
in Astroblast. It's similar to what Thomas used to detect paddles.

I guess I need to brush up on my 2600 games. I didn't know Astroblast
supported both paddles and joysticks.

DetermineControllerType
   lda #DUMP_PORTS | DISABLE_TIA
   sta VBLANK
   ldx #0
.waitForCapacitorCharge
   bit INPT0                        ; check paddle 0 value
   bpl LFB88                        ; branch if capacitor not charged
   dex
   bne .waitForCapacitorCharge
   beq .setControllerTypeToPaddles  ; unconditional branch
   
LFB88:
   lda #DISABLE_TIA
   sta VBLANK                       ; disable TIA (i.e. D1 = 1)
   ldx #32                          ; wait ~538 scanlines (i.e. ~2 frames)
.outerLoopWait
   ldy #0
.innerLoopWait
   iny
   bne .innerLoopWait
   dex
   bne .outerLoopWait
   bit INPT0                        ; check paddle 0 value
   bpl .doneDetermineControllerType ; branch if capacitor not charged
.setControllerTypeToPaddles
   lda gameState                    ; get current game state value
   ora #USING_PADDLES
   sta gameState                    ; set game state to USING_PADDLES
.doneDetermineControllerType
   rts

Take care,
Dennis