********************************************************************
* JoyDrv - Joystick Driver for CoCo 3 Hi-Res Mouse
*
* $Id$
*
* Ed.    Comments                                       Who YY/MM/DD
* ------------------------------------------------------------------
* 6      L2 Upgrade distribution version
*        Annotations by Robert Gault                    RG  98/10/09

         nam   JoyDrv
         ttl   Joystick Driver for CoCo 3 Hi-Res Mouse

* Disassembled 98/09/09 09:07:45 by Disasm v1.6 (C) 1988 by RML

         ifp1  
         use   defsfile
         endc  

tylg     set   Systm+Objct
atrv     set   ReEnt+rev
rev      set   $01
edition  set   6

         mod   eom,name,tylg,atrv,start,size
size     equ   .

name     fcs   /JoyDrv/
         fcb   edition

start    lbra  Init       setup for special button state & clear buttons
         lbra  Term       clear button but don't change special flag
         lbra  SSMsBtn    read and process button values
         lbra  SSMsXY    read joystick values; with processing
         lbra  SSJoyBtn  clear keyboard input and return raw button info

SSJoyXY  pshs  y,x,b,a    read joystick values
         pshs  x,b,a
         ldx   #PIA0Base  point to PIA#1
         lda   <$23,x     read sound enable state?
         ldb   <$20,x     read 6-bit DAC
         pshs  b,a        save current states
         anda  #%11110111 clear sound enable
         sta   <$23,x     set switch
         lda   $01,x      read MUX SEL#1
         ldb   $03,x      read MUX SEL#2
         pshs  b,a        save current state
         orb   #$08       set SEL#2
         lda   $08,s      read ?what?
         anda  #$02       keep only left or right joystick
         bne   L0047      if left then don't
         andb  #%11110111 clear SEL#2
L0047    stb   $03,x      enable SEL#2 value
         leay  <L0097,pcr point to high res routine
         ldb   $0D,s      flag for high/low res
         bne   L0054
         leay  >L010F,pcr point to low res routine
L0054    lda   ,s
         ora   #$08       set MUX SEL#1
         jsr   ,y         read pot
         tst   $0D,s      here the same byte seems to be used for x/y flag??
         beq   L0060
         bsr   L00DB      convert from width to height value
L0060    std   $06,s      return joystick value
         lda   ,s         now read the other direction
         anda  #$F7       flip the MUX SEL#1 bit
         jsr   ,y         read the second pot
         std   $04,s      save the other value
         puls  b,a
         sta   $01,x
         stb   $03,x
         puls  b,a
         stb   <$20,x     reset the DAC and sound selector
         sta   <$23,x
         puls  y,x
         lda   ,s         flag for double button?
         cmpa  #$01
         bne   L0094
         ldb   #$80       minimum flag
         lda   $05,s
         bne   L008B
         cmpx  #32        minimum joystick value
         bcc   L0092
L008B    cmpx  #320       maximum joystick value
         bcc   L0092      if less than don't change flag
         ldb   #$C0       maximum flag
L0092    stb   ,u         save max/min flag value
L0094    leas  $06,s
         rts   
L0097    pshs  cc         high res routine
         sta   $01,x      select x/y pot
         lda   #$FF       full DAC value
         sta   <$20,x     store in DAC to charge capacitor
         lda   #$5A       timing loop; wait for voltage to settle
L00A2    deca  
         bne   L00A2      wait
         ldd   #$0329
         pshs  a
         lda   #$02
         orcc  #IntMasks  kill interrupts
         sta   <$20,x     clear DAC; mask RS-232; start cap. discharge
L00B1    lda   ,x         test comparator
         bmi   L00C0
         decb             counter  
         bne   L00B1      loop until state change
         dec   ,s         3 -> 0
         bpl   L00B1      loop again
         puls  a
         bra   L00D6      branch to maximum value
L00C0    puls  a
         decb  
         pshs  b,a
         ldd   #640
         subd  ,s++       convert from 640 -> 0 to 0 -> 640
         bcc   L00D0
         clra             minimum value is $00  
         clrb  
         puls  pc,cc
L00D0    cmpd  #639
         bcs   L00D9
L00D6    ldd   #639       maximum value
L00D9    puls  pc,cc
* This routine converts a pot value from width (640) to height (192) to match
* possible screen values; ie. value divided by 3.33
L00DB    pshs  a
         lda   #$09
         pshs  a
         lda   #$03
         mul   
         pshs  b,a
         lda   $03,s
         ldb   #$03
         mul   
         exg   b,a
         addd  ,s++
L00EF    clr   $01,s
         cmpa  #$0A
         bcs   L00F9
         inc   $01,s
         suba  #$0A
L00F9    lsr   $01,s
         rolb  
         rola  
         dec   ,s
         bne   L00EF
         cmpb  #$BF
         beq   L010B
         cmpa  #$0A
         bcs   L010B
         addb  #$01
L010B    clra  
         leas  $02,s
         rts   
* Low res binary tree search for joystick value   
L010F    sta   $01,x      set MUX SEL#1
         lda   #$7F       DAC value
         ldb   #$40
         bra   L0122
L0117    lsrb             reset DAC offset value 
         cmpb  #$01
         bhi   L0122
         lsra  
         lsra  
         tfr   a,b
         clra  
         rts              return with voltage   
L0122    pshs  b
         sta   <$20,x     set DAC
         tst   ,x         test comparator
         bpl   L012F
         adda  ,s+        adjust binary tree search
         bra   L0117
L012F    suba  ,s+        adjust binary tree search
         bra   L0117

SSMsXY   leay  ,y         get flag??
         lbne  SSJoyXY    go read joystick pots
         lbsr  SSJoyXY    go read joystick pots and then convert values
         tfr   x,d        multiply regX by 10 and regY by 3
         lda   #$0A
         mul   
         tfr   d,x
         cmpx  #630
         bcs   L014B
         ldx   #634       maximum limit on regX
*	may be an error and could be 639
L014B    tfr   y,d
         lda   #$03
         mul   
         tfr   d,y
         rts   

Init     ldb   #$80
         stb   ,u

Term     clr   $01,u
         rts   

SSJoyBtn ldx   #PIA0Base  PIA#1 base address
         clrb  
         comb  
         stb   $02,x      clear PIA#1 key strobe lines
         ldb   ,x         read data lines
         comb             only buttons and comparator valid
         andb  #$0F       only buttons; 0=off 1=on
         rts   

SSMsBtn  bsr   SSJoyBtn
         tfr   b,a
         anda  #%11111010 regA=left buttons; should be $0A not $FA
         pshs  a          save left button values
         andb  #$05       regB=right buttons
         orb   $01,u      ORB with previous state??
         leax  <L0187,pcr point to sequential switch table possibilities
         lda   b,x
         anda  #%00001010 keep only left values
         sta   $01,u      save for change test
         ldb   b,x        repeat
         andb  #%10000101 keep flag and right values
         bpl   L0184
         ldb   ,u         previous min/max state
L0184    orb   ,s+        ORB with current left values and pop stack
         rts   
L0187    fcb   $00,$03,$00,$03,$08,$06,$02,$06,$80,$02,$00,$02,$08,$06,$0a,$06

         emod  
eom      equ   *
         end