C02/vcs/include/sticks.a02

;C02 VCS Library - Joystick Assembly Language Subroutines 

;getstk(cntrlr) - Read Joystick
;Args: A = Controller Number, 0=Left, 1=Right
;Sets: TEMP0 = Left Joystick Raw Directional Bits
;      TEMP1 = Right Joystick Raw Directional Bits
;      X = Controller Number
;Returns: A = Joystick Bits (1 if Pressed)
;             0=Up, 1=Down, 2=Left, 3=Right, 7=Trigger
;         N = Set if Trigger Pressed
;         Z = Set if No Buttons or Trigger Pressed
GETSTK: TAX             ;Save Stick Number in Index
        LDA SWCHA       ;Read Joystick Register
        LSR             ;Shift High Nybble into Low Nybble
        LSR
        LSR
        LSR
        STA TEMP0       ;Save Left Joystick Raw Bits
        LDA SWCHA       ;Read Joystick Register
        AND #$0F        ;Strip High Nybble
        STA TEMP1       ;Save Right Joystick Raw Bits
        LDA INPT4,X     ;Read Joystick Trigger
        AND #$80        ;Strip Bits 1-6
        ORA TEMP0,X     ;Combine with Directional Bits
        EOR #$8F        ;Reverse Bits
        RTS