emul/hw/sms: WIP

VDP kinda works. Can see the Collapse OS prompt with SMS base recipe
if `STDIO_GETC` gets replaced with infinite loop (no input emul yet).

apps/lib/parse.asm

@@ -21,7 +21,6 @@ parseHex:
 	add	a, 10		; C is clear, map back to 0xA-0xF
 	ret
 
-
 ; Parse string at (HL) as a decimal value and return value in DE.
 ; Reads as many digits as it can and stop when:
 ; 1 - A non-digit character is read
@@ -44,10 +43,10 @@ parseDecimal:
 	; During this routine, we switch between HL and its shadow. On one side,
 	; we have HL the string pointer, and on the other side, we have HL the
 	; numerical result. We also use EXX to preserve BC, saving us a push.
+parseDecimalSkip:	; enter here to skip parsing the first digit
 	exx		; HL as a result
 	ld	h, 0
 	ld	l, a	; load first digit in without multiplying
-	ld	b, 0	; We use B to detect overflow
 
 .loop:
 	exx		; HL as a string pointer
@@ -60,24 +59,22 @@ parseDecimal:
 	sub	0xff-9
 	jr	c, .end	
 
+	ld	b, a	; we can now use a for overflow checking
 	add	hl, hl	; x2
-	; We do this to detect overflow at each step
+	sbc	a, a	; a=0 if no overflow, a=0xFF otherwise
-	rl	b
 	ld	d, h
 	ld	e, l		; de is x2
 	add	hl, hl	; x4
-	rl	b
+	rla
 	add	hl, hl	; x8
-	rl	b
+	rla
 	add	hl, de	; x10
-	rl	b
+	rla
-	ld	d, 0
+	ld	d, a	; a is zero unless there's an overflow
-	ld	e, a
+	ld	e, b
 	add	hl, de
-	rl	b
+	adc	a, a	; same as rla except affects Z
 	; Did we oveflow?
-	xor	a
-	or	b
 	jr	z, .loop	; No? continue
 	; error, NZ already set
 	exx		; HL is now string pointer, restore BC
@@ -106,33 +103,49 @@ parseDecimalC:
 ; Sets Z on success.
 parseHexadecimal:
 	ld	a, (hl)
-	call	parseHex
+	call	parseHex	; before "ret c" is "sub 0xfa" in parseHex
-	jp	c, unsetZ	; we need at least one char
+				; so carry implies not zero
+	ret 	c	; we need at least one char
 	push	bc
 	ld	de, 0
-	ld	b, 0
+	ld	b, d
+	ld	c, d
+
+; The idea here is that the 4 hex digits of the result can be represented "bdce",
+; where each register holds a single digit. Then the result is simply
+; e = (c << 4) | e,	 d = (b << 4) | d
+; However, the actual string may be of any length, so when loading in the most
+; significant digit, we don't know which digit of the result it actually represents
+; To solve this, after a digit is loaded into a (and is checked for validity),
+; all digits are moved along, with e taking the latest digit.
 .loop:
-	; we push to B to verify overflow
+	dec 	b
-	rl	e \ rl d \ rl b
+	inc 	b	; b should be 0, else we've overflowed
-	rl	e \ rl d \ rl b
+	jr	nz, .end	; Z already unset if overflow
-	rl	e \ rl d \ rl b
+	ld 	b, d
-	rl	e \ rl d \ rl b
+	ld 	d, c
-	or	e
+	ld 	c, e
-	ld	e, a
+	ld 	e, a
-	; did we overflow?
+	inc 	hl
-	ld	a, b
+	ld 	a, (hl)
-	or	a
+	call 	parseHex
-	jr	nz, .end	; overflow, NZ already set
+	jr 	nc, .loop
-	; next char
+	ld 	a, b
-	inc	hl
+	add	a, a  \ add a, a \ add a, a \ add a, a
-	ld	a, (hl)
+	or 	d
-	call	parseHex
+	ld 	d, a
-	jr	nc, .loop
+
-	cp	a		; ensure Z
+	ld 	a, c
+	add	a, a  \ add a, a \ add a, a \ add a, a
+	or 	e
+	ld 	e, a
+	xor	a	; ensure z
+
 .end: 
 	pop	bc
 	ret
 
+
 ; Parse string at (HL) as a binary value (010101) without the "0b" prefix and
 ; return value in E. D is always zero.
 ; HL is advanced to the character following the last successfully read char.
@@ -144,10 +157,10 @@ parseBinaryLiteral:
 	add	a, 0xff-'1'
 	sub	0xff-1
 	jr	c, .end
-	rl	e
+	rlc	e	; sets carry if overflow, and affects Z
+	ret	c	; Z unset if carry set, since bit 0 of e must be set
 	add	a, e
 	ld	e, a
-	jp	c, unsetZ	; overflow
 	inc	hl
 	jr	.loop
 .end:
@@ -167,10 +180,13 @@ parseLiteral:
 	ld	a, (hl)
 	cp	0x27		; apostrophe
 	jr	z, .char
-	call	isDigit
+
-	ret	nz
+	; inline parseDecimalDigit
-	cp	'0'
+	add 	a, 0xc6	; maps '0'-'9' onto 0xf6-0xff
-	jp	nz, parseDecimal
+	sub 	0xf6	; maps to 0-9 and carries if not a digit
+	ret	c
+	; a already parsed so skip first few instructions of parseDecimal
+	jp	nz, parseDecimalSkip	
 	; maybe hex, maybe binary
 	inc	hl
 	ld	a, (hl)
@@ -195,14 +211,13 @@ parseLiteral:
 	ld	e, (hl)		; our result
 	inc	hl
 	cp	(hl)
-	jr	nz, .charError	; not ending with an apostrophe
+	; advance HL and return if good char
-	; good char, advance HL and return
 	inc	hl
-	; Z already set
+	ret	z
-	ret
+
-.charError:
+	; Z unset and there's an error
-	; In all error conditions, HL is advanced by 2. Rewind.
+	; In all error conditions, HL is advanced by 3. Rewind.
-	dec	hl \ dec hl
+	dec	hl \ dec hl \ dec hl
 	; NZ already set
 	ret
 
@@ -215,9 +230,9 @@ isLiteralPrefix:
 
 ; Returns whether A is a digit
 isDigit:
-	cp	'0'
+	cp	'0'	; carry implies not zero for cp
-	jp	c, unsetZ
+	ret 	c
-	cp	'9'+1
+	cp	'9'	; zero unset for a > '9', but set for a='9'
-	jp	nc, unsetZ
+	ret	nc
 	cp	a	; ensure Z
 	ret

emul/hw/sms/.gitignore

@@ -0,0 +1 @@
+/sms

emul/hw/sms/Makefile

@@ -0,0 +1,15 @@
+EXTOBJS = ../../emul.o ../../libz80/libz80.o
+OBJS = sms.o vdp.o
+TARGET = sms
+CFLAGS += `pkg-config --cflags xcb`
+
+.PHONY: all
+all: $(TARGET)
+
+$(TARGET): $(OBJS) $(EXTOBJS)
+	$(CC) `pkg-config --libs xcb` $(OBJS) $(EXTOBJS) -o $@
+
+.PHONY: clean
+clean:
+	rm -f $(TARGET) $(OBJS)
+	

emul/hw/sms/sms.c

@@ -0,0 +1,194 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+#include <xcb/xcb.h>
+
+#include "../../emul.h"
+#include "vdp.h"
+
+#define RAMSTART 0xc000
+#define VDP_CMD_PORT 0xbf
+#define VDP_DATA_PORT 0xbe
+#define MAX_ROMSIZE 0x8000
+
+static xcb_connection_t    *conn;
+static xcb_screen_t        *screen;
+
+/* graphics contexts */
+static xcb_gcontext_t       fg;
+/* win */
+static xcb_drawable_t       win;
+
+// pixels to draw. We draw them in one shot.
+static xcb_rectangle_t rectangles[VDP_SCREENW*VDP_SCREENH];
+
+static Machine *m;
+static VDP vdp;
+static bool vdp_changed;
+
+static uint8_t iord_vdp_cmd()
+{
+    return vdp_cmd_rd(&vdp);
+}
+
+static uint8_t iord_vdp_data()
+{
+    return vdp_data_rd(&vdp);
+}
+
+static void iowr_vdp_cmd(uint8_t val)
+{
+    vdp_cmd_wr(&vdp, val);
+}
+
+static void iowr_vdp_data(uint8_t val)
+{
+    vdp_changed = true;
+    vdp_data_wr(&vdp, val);
+}
+
+void create_window()
+{
+    uint32_t mask;
+    uint32_t values[2];
+
+    /* Create the window */
+    win = xcb_generate_id(conn);
+    mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
+    values[0] = screen->white_pixel;
+    values[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_KEY_PRESS |
+        XCB_EVENT_MASK_KEY_RELEASE;
+    xcb_create_window(
+        conn,
+        screen->root_depth,
+        win,
+        screen->root,
+        0, 0,
+        150, 150,
+        10,
+        XCB_WINDOW_CLASS_INPUT_OUTPUT,
+        screen->root_visual,
+        mask, values);
+
+    fg = xcb_generate_id(conn);
+    mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
+    values[0] = screen->black_pixel;
+    values[1] = 0;
+    xcb_create_gc(conn, fg, screen->root, mask, values);
+
+    /* Map the window on the screen */
+    xcb_map_window(conn, win);
+}
+
+void draw_pixels()
+{
+    xcb_get_geometry_reply_t *geom;
+
+    geom = xcb_get_geometry_reply(conn, xcb_get_geometry(conn, win), NULL);
+
+    xcb_clear_area(
+        conn, 0, win, 0, 0, geom->width, geom->height);
+    // Figure out inner size to maximize our screen's aspect ratio
+    int psize = geom->height / VDP_SCREENH;
+    if (geom->width / VDP_SCREENW < psize) {
+        // width is the constraint
+        psize = geom->width / VDP_SCREENW;
+    }
+    int innerw = psize * VDP_SCREENW;
+    int innerh = psize * VDP_SCREENH;
+    int innerx = (geom->width - innerw) / 2;
+    int innery = (geom->height - innerh) / 2;
+    int drawcnt = 0;
+    for (int i=0; i<VDP_SCREENW; i++) {
+        for (int j=0; j<VDP_SCREENH; j++) {
+            if (vdp_pixel(&vdp, i, j)) {
+                int x = innerx + (i*psize);
+                int y = innery + (j*psize);
+                rectangles[drawcnt].x = x;
+                rectangles[drawcnt].y = y;
+                rectangles[drawcnt].height = psize;
+                rectangles[drawcnt].width = psize;
+                drawcnt++;
+            }
+        }
+    }
+    if (drawcnt) {
+        xcb_poly_fill_rectangle(
+            conn, win, fg, drawcnt, rectangles);
+    }
+    vdp_changed = false;
+    xcb_flush(conn);
+}
+
+void event_loop()
+{
+    while (1) {
+        emul_step();
+        if (vdp_changed) {
+            // To avoid overdrawing, we'll let the CPU run a bit to finish its
+            // drawing operation.
+            emul_steps(100);
+            draw_pixels();
+        }
+        xcb_generic_event_t *e = xcb_poll_for_event(conn);
+        if (!e) {
+            continue;
+        }
+        switch (e->response_type & ~0x80) {
+        /* ESC to exit */
+        case XCB_KEY_RELEASE:
+        case XCB_KEY_PRESS: {
+            xcb_key_press_event_t *ev = (xcb_key_press_event_t *)e;
+            if (ev->detail == 0x09) return;
+            break;
+        }
+        case XCB_EXPOSE: {
+            draw_pixels();
+            break;
+        }
+        default: {
+            break;
+        }
+        }
+        free(e);
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./sms /path/to/rom\n");
+        return 1;
+    }
+    FILE *fp = fopen(argv[1], "r");
+    if (fp == NULL) {
+        fprintf(stderr, "Can't open %s\n", argv[1]);
+        return 1;
+    }
+    m = emul_init();
+    m->ramstart = RAMSTART;
+    int i = 0;
+    int c;
+    while ((c = fgetc(fp)) != EOF && i < MAX_ROMSIZE) {
+        m->mem[i++] = c & 0xff;
+    }
+    pclose(fp);
+    if (c != EOF) {
+        fprintf(stderr, "ROM image too large.\n");
+        return 1;
+    }
+    vdp_init(&vdp);
+    vdp_changed = false;
+    m->iord[VDP_CMD_PORT] = iord_vdp_cmd;
+    m->iord[VDP_DATA_PORT] = iord_vdp_data;
+    m->iowr[VDP_CMD_PORT] = iowr_vdp_cmd;
+    m->iowr[VDP_DATA_PORT] = iowr_vdp_data;
+    conn = xcb_connect(NULL, NULL);
+    screen = xcb_setup_roots_iterator(xcb_get_setup(conn)).data;
+    create_window();
+    draw_pixels();
+    event_loop();
+    emul_printdebug();
+    return 0;
+}

emul/hw/sms/vdp.c

@@ -0,0 +1,77 @@
+#include <string.h>
+#include "vdp.h"
+
+void vdp_init(VDP *vdp)
+{
+    memset(vdp->vram, 0, VDP_VRAM_SIZE);
+    memset(vdp->regs, 0, 0x10);
+    vdp->has_cmdlsb = false;
+    vdp->curaddr = 0;
+}
+
+uint8_t vdp_cmd_rd(VDP *vdp)
+{
+    return 0;
+}
+
+void vdp_cmd_wr(VDP *vdp, uint8_t val)
+{
+    if (!vdp->has_cmdlsb) {
+        vdp->cmdlsb = val;
+        vdp->has_cmdlsb = true;
+        return;
+    }
+    vdp->has_cmdlsb = false;
+    if ((val & 0xc0) == 0x80) {
+        // set register
+        vdp->regs[val&0xf] = vdp->cmdlsb;
+    } else if ((val & 0xc0) == 0xc0) {
+        // palette RAM
+        vdp->curaddr = 0x4000 + (vdp->cmdlsb&0x1f);
+    } else {
+        // VRAM
+        vdp->curaddr = ((val&0x3f) << 8) + vdp->cmdlsb;
+    }
+}
+
+uint8_t vdp_data_rd(VDP *vdp)
+{
+    uint8_t res = vdp->vram[vdp->curaddr];
+    if (vdp->curaddr < VDP_VRAM_SIZE) {
+        vdp->curaddr++;
+    }
+    return res;
+}
+
+void vdp_data_wr(VDP *vdp, uint8_t val)
+{
+    vdp->vram[vdp->curaddr] = val;
+    if (vdp->curaddr < VDP_VRAM_SIZE) {
+        vdp->curaddr++;
+    }
+}
+
+uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
+{
+    if (x >= VDP_SCREENW) {
+        return 0;
+    }
+    if (y >= VDP_SCREENH) {
+        return 0;
+    }
+    // name table offset
+    uint16_t offset = 0x3800 + ((y/8) << 6) + ((x/8) << 1);
+    uint16_t tableval = vdp->vram[offset] + (vdp->vram[offset+1] << 8);
+    uint16_t tilenum = tableval & 0x1ff;
+    // tile offset this time. Each tile is 0x20 bytes long.
+    offset = tilenum * 0x20;
+    // Each 4 byte is a row. Find row first.
+    offset += ((y%8) * 4);
+    uint8_t bitnum = 7 - (x%8);
+    // Now, let's compose the result by pushing the right bit of our 4 bytes
+    // into our result.
+    return ((vdp->vram[offset] >> bitnum) & 1) + \
+           (((vdp->vram[offset+1] >> bitnum) & 1) << 1) + \
+           (((vdp->vram[offset+2] >> bitnum) & 1) << 2) + \
+           (((vdp->vram[offset+3] >> bitnum) & 1) << 3);
+}

emul/hw/sms/vdp.h

@@ -0,0 +1,26 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+#define VDP_VRAM_SIZE 0x4020
+#define VDP_SCREENW (32*8)
+#define VDP_SCREENH (24*8)
+// Offset of the name table
+#define VDP_NTABLE_OFFSET 0x3800
+
+
+typedef struct {
+    // the last 0x20 is palette RAM
+    uint8_t vram[VDP_VRAM_SIZE];
+    uint8_t regs[0x10];
+    uint8_t cmdlsb;
+    bool has_cmdlsb;
+    uint16_t curaddr;
+} VDP;
+
+void vdp_init(VDP *vdp);
+uint8_t vdp_cmd_rd(VDP *vdp);
+void vdp_cmd_wr(VDP *vdp, uint8_t val);
+uint8_t vdp_data_rd(VDP *vdp);
+void vdp_data_wr(VDP *vdp, uint8_t val);
+// result is a RGB value
+uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y);

kernel/sms/vdp.asm

@@ -38,6 +38,7 @@ vdpInit:
 	ld	c, VDP_CTLPORT
 	otir
 
+	; Blank VRAM
 	xor	a
 	out	(VDP_CTLPORT), a
 	ld	a, 0x40
@@ -51,15 +52,17 @@ vdpInit:
 	or	c
 	jr	nz, .loop1
 
+	; Set palettes
 	xor	a
 	out	(VDP_CTLPORT), a
 	ld	a, 0xc0
 	out	(VDP_CTLPORT), a
-	ld	hl, vdpPaletteData
+	xor	a			; palette 0: black
-	ld	b, vdpPaletteDataEnd-vdpPaletteData
+	out	(VDP_DATAPORT), a
-	ld	c, VDP_DATAPORT
+	ld	a, 0x3f			; palette 1: white
-	otir
+	out	(VDP_DATAPORT), a
 
+	; Define tiles
 	xor	a
 	out	(VDP_CTLPORT), a
 	ld	a, 0x40
@@ -97,6 +100,7 @@ vdpInit:
 	dec	c
 	jr	nz, .loop2
 
+	; Bit 7 = ?, Bit 6 = display enabled
 	ld	a, 0b11000000
 	out	(VDP_CTLPORT), a
 	ld	a, 0x81
@@ -129,7 +133,7 @@ vdpSpitC:
 				; two bits
 	out	(VDP_CTLPORT), a
 	ld	a, b		; 3 low bits set
-	or	0x78
+	or	0x78		; 01 header + 0x3800
 	out	(VDP_CTLPORT), a
 	pop	bc
 
@@ -279,11 +283,16 @@ vdpConv:
 	ld	a, 0x5e
 	ret
 
-vdpPaletteData:
-.db 0x00,0x3f
-vdpPaletteDataEnd:
-
 ; VDP initialisation data
 vdpInitData:
-.db 0x04,0x80,0x00,0x81,0xff,0x82,0xff,0x85,0xff,0x86,0xff,0x87,0x00,0x88,0x00,0x89,0xff,0x8a
+; 0x8x == set register X
+.db 0b00000100, 0x80	; Bit 2: Select mode 4
+.db 0b00000000, 0x81
+.db 0b11111111, 0x82	; Name table: 0x3800
+.db 0b11111111, 0x85	; Sprite table: 0x3f00
+.db 0b11111111, 0x86	; sprite use tiles from 0x2000
+.db 0b11111111, 0x87	; Border uses palette 0xf
+.db 0b00000000, 0x88	; BG X scroll
+.db 0b00000000, 0x89	; BG Y scroll
+.db 0b11111111, 0x8a	; Line counter (why have this?)
 vdpInitDataEnd: