sms: Pad WIP

blk/620

@@ -1,3 +1,3 @@
 Sega Master System Recipe
 
-622 VDP
+622 VDP                        630 PAD

blk/622

@@ -13,4 +13,4 @@ the screen is reached, we wrap up to the top.
 When reaching a new line, we clear that line and the next to
 help readability.
 
-Load range: 623-623
+Load range: 623-628

blk/630

@@ -0,0 +1,16 @@
+Pad driver - read input from MD controller
+
+Conveniently expose an API to read the status of a MD pad A.
+Moreover, implement a mechanism to input arbitrary characters
+from it. It goes as follow:
+
+* Direction pad select characters. Up/Down move by one,
+  Left/Right move by 5
+* Start acts like Return
+* A acts like Backspace
+* B changes "character class": lowercase, uppercase, numbers,
+  special chars. The space character is the first among special
+  chars.
+* C confirms letter selection
+
+                                                        (cont.)

blk/631

@@ -0,0 +1,6 @@
+This module is currently hard-wired to VDP driver, that is, it
+calls vdp's routines during (key) to update character
+selection.
+
+Load range: 632-637
+

blk/632

@@ -0,0 +1,12 @@
+: _prevstat [ PAD_MEM LITN ] ;
+: _sel [ PAD_MEM 1+ LITN ] ;
+: _next [ PAD_MEM 2+ LITN ] ;
+
+( Put status for port A in register A. Bits, from MSB to LSB:
+Start - A - C - B - Right - Left - Down - Up
+Each bit is high when button is unpressed and low if button is
+pressed. When no button is pressed, 0xff is returned.
+This logic below is for the Genesis controller, which is modal.
+TH is an output pin that swiches the meaning of TL and TR. When
+TH is high (unselected), TL = Button B and TR = Button C. When
+TH is low (selected), TL = Button A and TR = Start. )

blk/633

@@ -0,0 +1,15 @@
+CODE _status
+    A 0b11111101 LDrn, ( TH output, unselected )
+    PAD_CTLPORT OUTnA,
+    PAD_D1PORT INAn,
+    0x3f ANDn, ( low 6 bits are good )
+    B A LDrr,  ( let's store them )
+( Start and A are returned when TH is selected, in bits 5 and
+  4. Well get them, left-shift them and integrate them to B. )
+    A 0b11011101 LDrn, ( TH output, selected )
+    PAD_CTLPORT OUTnA,
+    PAD_D1PORT INAn,
+    0b00110000 ANDn,
+    A SLAr, A SLAr, B ORr,
+    PUSHA,
+;CODE

blk/634

@@ -0,0 +1,5 @@
+: _chk ( c --, check _sel range )
+    _sel C@ DUP 0x7f > IF 0x20 _sel C! THEN
+    0x20 < IF 0x7f _sel C! THEN ;
+: _nxtcls
+;

blk/635

@@ -0,0 +1,13 @@
+: _updsel ( -- f, has an action button been pressed? )
+    _status _prevstat C@ OVER = IF DROP 0 EXIT THEN
+    DUP _prevstat C! ( changed, update ) ( s )
+    0x01 ( UP ) OVER AND NOT IF 1 _sel +! THEN
+    0x02 ( DOWN ) OVER AND NOT IF -1 _sel +! THEN
+    0x04 ( LEFT ) OVER AND NOT IF -5 _sel +! THEN
+    0x08 ( RIGHT ) OVER AND NOT IF 5 _sel +! THEN
+    0x10 ( BUTB ) OVER AND NOT IF _nxtcls THEN
+    ( update sel in VDP )
+    _sel C@ (emit) -1 XYPOS +!
+    ( return whether any of the high 3 bits is low )
+    0xe0 AND 0xe0 <
+;

blk/636

@@ -0,0 +1,8 @@
+: (key)
+    BEGIN _updsel UNTIL
+    _prevstat C@
+    0x20 ( BUTC ) OVER AND NOT IF THEN
+    0x40 ( BUTA ) AND NOT IF THEN
+    ( If not BUTC or BUTA, it has to be START )
+    _sel C@
+;

blk/637

@@ -0,0 +1,2 @@
+: PAD$
+    0xff _prevstat C! 'a' _sel C! 0 _next C! ;

recipes/sms/xcomp.fs

@@ -8,6 +8,9 @@ RAMSTART 0x70 + CONSTANT VDP_MEM
 0xbe   CONSTANT VDP_DATAPORT
 32     CONSTANT VDP_COLS
 24     CONSTANT VDP_ROWS
+RAMSTART 0x72 + CONSTANT PAD_MEM
+0x3f   CONSTANT PAD_CTLPORT
+0xdc   CONSTANT PAD_D1PORT
 212 LOAD  ( z80 assembler )
 : ZFILL, ( u ) 0 DO 0 A, LOOP ;
 262 LOAD  ( xcomp )
@@ -23,11 +26,11 @@ CURRENT @ XCURRENT !
 393 LOAD  ( xcomp core low )
 CREATE ~FNT CPFNT7x7
 623 628 LOADR ( VDP )
-: (key) 4 ;
+632 637 LOADR ( PAD )
 420 LOAD  ( xcomp core high )
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
-," VDP$ " EOT,
+," VDP$ PAD$ " EOT,
 ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!