Add support for different joysticks

libsrc/atari7800/joy/atari7800-stdjoy.s

@@ -53,13 +53,20 @@ JOY_COUNT       = 2             ; Number of joysticks we support
 ; Must return an JOY_ERR_xx code in a/x.
 ;
 
+PB2 = $04 ; Joystick 0
+PB4 = $10 ; Joystick 1
+
 INSTALL:
         ; Assume 7800 2-button controller, can change
         ; to 2600 1-button later
-        lda #$14
-        sta CTLSWB ; enable 2-button 7800 controller 1: set pin 6 to output
+        lda #(PB2 | PB4)
+        ; enable 2-button 7800 controllers on both ports
+        ; by setting PB2 and PB4 to output
+        sta CTLSWB
+        ; enable 2-button 7800 controllers by setting
+        ; the outputs to 0; (INPT4 and INPT5) high
         ldy #$00
-        sty SWCHB ; enable 2-button 7800 controller 2: pull pin 6 (INPT4) high
+        sty SWCHB
 
 reset:
         lda #JOY_ERR_OK
@@ -88,6 +95,28 @@ COUNT:
 ; ------------------------------------------------------------------------
 ; READ: Read a particular joystick passed in A for 2 fire buttons.
 
+readdualbuttons0:
+    ldy #0      ; ........
+    bit INPT0   ; Check for right button
+    bpl L1
+    ldy #2      ; ......2.
+L1: bit INPT1   ; Check for left button
+    bpl L2
+    iny         ; ......21
+L2: tya
+    rts
+
+readdualbuttons1:
+    ldy #0      ; ........
+    bit INPT2   ; Check for right button
+    bpl L1
+    ldy #2      ; ......2.
+L3: bit INPT3   ; Check for left button
+    bpl L2
+    iny         ; ......21
+L4: tya
+    rts
+
 readbuttons:
     ; Y has joystick of interest 0/1
     ; return value:
@@ -97,42 +126,48 @@ readbuttons:
     ;  $03: both buttons
     ; preserves X
     tya
-    beq L5
+    beq readbuttons0
+readbuttons1:
     ; Joystick 1 processing
-    ; 7800 joystick 1 buttons
-    ldy #0      ; ........
-    bit INPT2   ; Check for right button
-    bpl L1
-    ldy #2      ; ......2.
-L1: bit INPT3   ;Check for left button
-    bpl L2
-    iny         ; ......21
-L2: tya
-    bne L4      ; 7800 mode joystick worked
-    ; 2600 Joystick 1
+    ; Start by checking for single button 2600 joystick
     bit INPT5
-    bmi L4
-L3: iny         ; .......1
-    lda #0      ; Fallback to 2600 joystick mode
-    sta CTLSWB
-L4: tya         ; ......21
+    bpl singlebtn1detected
+    jmp readdualbuttons1
+singlebtn1detected:
+    ; Single button joystick detected but could be dual
+    jsr readdualbuttons1
+    bne L5      ; It was a dual button press
+    ; It was a single button press
+    bit INPT5
+    bmi L5
+    iny         ; .......1
+    lda #PB4    ; Joystick 1 is a single button unit
+    clc
+    adc SWCHB
+    sta SWCHB   ; Cut power from the dual button circuit
+L5: tya         ; ......21
     rts
 
-L5: ; Joystick 0 processing
-    ; 7800 joystick 0 buttons
-    ldy #0      ; ........
-    bit INPT0   ; Check for right button
-    bpl L6
-    ldy #2      ; ......2.
-L6: bit INPT1   ;Check for left button
-    bpl L7
-    iny         ; ......21
-L7: tya
-    bne L4      ; 7800 mode joystick worked
-    ; 2600 Joystick 0
+readbuttons0:
+    ; Joystick 0 processing
+    ; Start by checking for single button 2600 joystick
     bit INPT4
-    bmi L4
-    bpl L3
+    bpl singlebtn0detected
+    jmp readdualbuttons0
+singlebtn0detected:
+    ; Single button joystick detected but could be dual
+    jsr readdualbuttons0
+    bne L6      ; It was a dual button press
+    ; It was a single button press
+    bit INPT4
+    bmi L6
+    iny         ; .......1
+    lda #PB2    ; Joystick 0 is a single button unit
+    clc
+    adc SWCHB
+    sta SWCHB   ; Cut power from the dual button circuit
+L6: tya         ; ......21
+    rts
 
 READ:
     tay         ; Store joystick 0/1 in Y