start work on multiplayer mode

src/main.c

@@ -39,6 +39,7 @@
 #include "sample.h"
 #include "window.h"
 #include "gbprinter.h"
+#include "multiplayer.h"
 #include "main.h"
 
 uint8_t debug_menu_index = 0;
@@ -116,6 +117,12 @@ static void about_screen(void) NONBANKED {
     while (1) {
         key_read();
 
+        if (mp_master_ready()) {
+            mp_master_start();
+            break;
+        }
+        win_about_mp();
+
         if (key_pressed(J_A) || key_pressed(J_B) || key_pressed(J_SELECT)) {
             break;
         }
@@ -313,6 +320,12 @@ static void splash(void) NONBANKED {
     while (1) {
         key_read();
 
+        if (mp_slave_ready()) {
+            mp_slave_start();
+            splash_win();
+        }
+        win_splash_mp();
+
         if (key_pressed(J_LEFT) && (!(conf_get()->debug_flags & DBG_MENU))) {
             highscore(1);
             splash_win();

src/main.h

@@ -4,9 +4,6 @@
  *
  * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
  *
- * Based on examples from gbdk-2020:
- * https://github.com/gbdk-2020/gbdk-2020/blob/develop/gbdk-lib/examples/gb/rand/rand.c
- *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or

src/multiplayer.c

@@ -0,0 +1,144 @@
+/*
+ * multiplayer.c
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#include "game.h"
+#include "timer.h"
+#include "multiplayer.h"
+
+#define MASTER_HELLO 0x42
+#define SLAVE_HELLO 0x23
+
+#define RETRANSMIT_TIME 200
+
+enum mp_state {
+    MP_M_SEND = 0,
+    MP_M_WAIT = 1,
+    MP_M_REPLY = 2,
+
+    MP_S_START = 0,
+    MP_S_WAIT = 1,
+    MP_S_REPLY = 2,
+};
+
+static enum mp_state state = 0;
+static uint16_t next_t = 0;
+
+uint8_t mp_connection_status = 0;
+
+uint8_t mp_master_ready(void) BANKED {
+    switch (state) {
+        case MP_M_SEND:
+            SB_REG = MASTER_HELLO;
+            SC_REG = SIOF_XFER_START | SIOF_CLOCK_INT;
+            next_t = timer_get() + RETRANSMIT_TIME;
+            mp_connection_status++;
+            state = MP_M_WAIT;
+            break;
+
+        case MP_M_WAIT:
+            if (!(SC_REG & SIOF_XFER_START)) {
+                if (SB_REG == SLAVE_HELLO) {
+                    SB_REG = SLAVE_HELLO;
+                    SC_REG = SIOF_XFER_START | SIOF_CLOCK_EXT;
+                    next_t = timer_get() + RETRANSMIT_TIME;
+                    mp_connection_status++;
+                    state = MP_M_REPLY;
+                }
+            }
+            if (timer_get() >= next_t) {
+                state = MP_M_SEND;
+            }
+            break;
+
+        case MP_M_REPLY:
+            if (!(SC_REG & SIOF_XFER_START)) {
+                if (SB_REG == MASTER_HELLO) {
+                    return 1;
+                } else {
+                    state = MP_M_SEND;
+                }
+            }
+            if (timer_get() >= next_t) {
+                state = MP_M_SEND;
+            }
+            break;
+
+        default:
+            state = 0;
+            break;
+    }
+
+    return 0;
+}
+
+void mp_master_start(void) BANKED {
+    game(); // TODO
+    state = 0;
+}
+
+uint8_t mp_slave_ready(void) BANKED {
+    switch (state) {
+        case MP_S_START:
+            SB_REG = SLAVE_HELLO;
+            SC_REG = SIOF_XFER_START | SIOF_CLOCK_EXT;
+            next_t = timer_get() + RETRANSMIT_TIME;
+            mp_connection_status++;
+            state = MP_S_WAIT;
+            break;
+
+        case MP_S_WAIT:
+            if (!(SC_REG & SIOF_XFER_START)) {
+                if (SB_REG == MASTER_HELLO) {
+                    SB_REG = MASTER_HELLO;
+                    SC_REG = SIOF_XFER_START | SIOF_CLOCK_INT;
+                    next_t = timer_get() + RETRANSMIT_TIME;
+                    mp_connection_status++;
+                    state = MP_S_REPLY;
+                } else {
+                    state = MP_S_START;
+                }
+            }
+            if (timer_get() >= next_t) {
+                state = MP_S_START;
+            }
+            break;
+
+        case MP_S_REPLY:
+            if (!(SC_REG & SIOF_XFER_START)) {
+                if (SB_REG == SLAVE_HELLO) {
+                    return 1;
+                }
+            }
+            if (timer_get() >= next_t) {
+                state = MP_S_START;
+            }
+            break;
+
+        default:
+            state = 0;
+            break;
+    }
+
+    return 0;
+}
+
+void mp_slave_start(void) BANKED {
+    game(); // TODO
+    state = 0;
+}

src/multiplayer.h

@@ -0,0 +1,33 @@
+/*
+ * multiplayer.h
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __MULTIPLAYER_H__
+#define __MULTIPLAYER_H__
+
+#include <gbdk/platform.h>
+#include <stdint.h>
+
+uint8_t mp_master_ready(void) BANKED;
+void mp_master_start(void) BANKED;
+uint8_t mp_slave_ready(void) BANKED;
+void mp_slave_start(void) BANKED;
+
+extern uint8_t mp_connection_status;
+
+#endif // __MULTIPLAYER_H__

src/window.c

@@ -33,6 +33,7 @@
 #include "git.h"
 #include "main.h"
 #include "gbprinter.h"
+#include "multiplayer.h"
 #include "window.h"
 
 #define MAX_DIGITS 7
@@ -259,6 +260,17 @@ void win_splash_draw(int32_t lowest, int32_t highest) BANKED {
     }
 }
 
+void win_splash_mp(void) BANKED {
+    /*
+    static uint8_t prev = 0;
+    if ((_cpu == CGB_TYPE) && (mp_connection_status != prev)) {
+        prev = mp_connection_status;
+        char c = (mp_connection_status & 0x01) ? 0x01 : 0x02;
+        str_ascii_l(&c, 1, 7, 2);
+    }
+    */
+}
+
 void win_score_clear(uint8_t is_black) BANKED {
     set_win_based(0, 0,
                   title_map_WIDTH / title_map_TILE_W, title_map_HEIGHT / title_map_TILE_H,
@@ -327,6 +339,9 @@ void win_about(void) BANKED {
         str_ascii(__DATE__, 0, 11);
         str_ascii(__TIME__, 0, 12);
 
+        str_ascii("MP Tx:", 14, 11);
+        str_ascii("Wait", 14, 12);
+
         str_ascii("Visit:", 0, 15);
         str_ascii("https://xythobuz.de", 0, 16);
     } else {
@@ -340,6 +355,15 @@ void win_about(void) BANKED {
     }
 }
 
+void win_about_mp(void) BANKED {
+    static uint8_t prev = 0;
+    if ((_cpu == CGB_TYPE) && (mp_connection_status != prev)) {
+        prev = mp_connection_status;
+        char c = (mp_connection_status & 0x01) ? 0x01 : 0x02;
+        str_ascii_l(&c, 1, 19, 12);
+    }
+}
+
 static uint8_t get_debug(char *name_buff, uint8_t i) NONBANKED {
     uint8_t n_len;
     START_ROM_BANK(BANK(main)) {

src/window.h

@@ -26,10 +26,12 @@
 
 void win_init(uint8_t is_splash);
 void win_splash_draw(int32_t lowest, int32_t highest) BANKED;
+void win_splash_mp(void) BANKED;
 void win_score_clear(uint8_t is_black) BANKED;
 void win_score_draw(struct scores score, uint8_t off, uint8_t is_black) BANKED;
 void win_score_print(uint8_t status) BANKED;
 void win_about(void) BANKED;
+void win_about_mp(void) BANKED;
 void win_conf(void) BANKED;
 void win_debug(void) BANKED;
 void win_name(int32_t score) BANKED;