fix(free): stop accompaniment on next even beat after fret release

In normal mode, releasing the fretboard now finishes the current beat-pair (beat 1→end of 2, beat 3→end of 4) instead of cutting immediately.

Co-authored-by: Cursor <cursoragent@cursor.com>

Global/Global.c

@@ -761,8 +761,106 @@ void Tap_to_Speed()
 }
 
 
+/* 普通模式松手：对齐到下一偶拍末再停（拍1→拍2末，拍3→拍4末）。
+ * piece 窗口 1920=4 拍，每拍 480 tick（与起奏 SetPiecePlayMode(1,0,1920) 一致）。 */
+#define FREE_BEAT_TICKS           480u
+#define FREE_PIECE_TICKS          1920u
+
+static uint8_t  s_free_even_stop_arm = 0;
+static uint64_t s_free_even_stop_tick = 0;
+static int      s_free_even_stop_beat = 2; /* 目标偶拍 2 或 4 */
+static uint8_t  s_free_even_seen_target = 0;
+
+static void FreeMode_CancelEvenBeatStop(void)
+{
+  s_free_even_stop_arm = 0;
+  s_free_even_stop_tick = 0;
+  s_free_even_stop_beat = 2;
+  s_free_even_seen_target = 0;
+}
+
+/* 再次按住指板：取消待停并恢复 piece 循环 */
+static void FreeMode_ResumePieceLoop(void)
+{
+  if (!s_free_even_stop_arm)
+    return;
+  FreeMode_CancelEvenBeatStop();
+  if (StartFlag && mGuiData[GUI_TAB_INDEX].Current == 2 &&
+      !mGuiData[GUI_AUTOBAND_SW].Current)
+  {
+    AutoBandTop1_SetPiecePlayMode(1, 0, FREE_PIECE_TICKS);
+    AutoBandTop1_SetLoopMode(0, 1);
+  }
+}
+
+static void FreeMode_ArmEvenBeatStop(void)
+{
+  uint64_t play;
+  int beat;
+  int target;
+
+  if (!StartFlag)
+  {
+    FreeMode_CancelEvenBeatStop();
+    return;
+  }
+
+  play = AutoBandTop1_GetCurrentPlayTick();
+  beat = AutoBandTop1_GetCurrentBeat();
+  if (beat < 1)
+    beat = 1;
+  /* 拍1→2，拍2→2，拍3→4，拍4→4 */
+  target = ((beat + 1) / 2) * 2;
+  s_free_even_stop_beat = target;
+  s_free_even_seen_target = (beat >= target) ? 1u : 0u;
+  /* ((beat0/2)+1)*2*480 → 拍1/2→960，拍3/4→1920，跨小节同理 */
+  s_free_even_stop_tick =
+      ((play / FREE_BEAT_TICKS) / 2ull + 1ull) * 2ull * (uint64_t)FREE_BEAT_TICKS;
+  s_free_even_stop_arm = 1;
+
+  /* 禁循环并裁 piece，库播到 stop tick 自停；Poll 作兜底 */
+  AutoBandTop1_SetLoopMode(0, 0);
+  if (s_free_even_stop_tick <= 0xFFFFFFFFull)
+    AutoBandTop1_SetPiecePlayMode(1, 0, (uint32_t)s_free_even_stop_tick);
+
+  LOG_I("pick", "free even-stop arm beat=%d target=%d play=%u stop=%u",
+        beat, target, (unsigned)play, (unsigned)s_free_even_stop_tick);
+}
+
+void FreeMode_PollEvenBeatStop(void)
+{
+  int beat;
+  uint8_t tick_done;
+  uint8_t beat_done;
+
+  if (!s_free_even_stop_arm)
+    return;
+  if (PressFlag || mGuiData[GUI_TAB_INDEX].Current != 2 || !StartFlag)
+  {
+    FreeMode_CancelEvenBeatStop();
+    return;
+  }
+
+  beat = AutoBandTop1_GetCurrentBeat();
+  if (beat == s_free_even_stop_beat)
+    s_free_even_seen_target = 1;
+  /* 已到达目标偶拍后离开该拍 = 该拍播完；或 play tick 到点 */
+  beat_done = (s_free_even_seen_target && beat != s_free_even_stop_beat && beat != 0) ? 1u : 0u;
+  tick_done = (AutoBandTop1_GetCurrentPlayTick() >= s_free_even_stop_tick) ? 1u : 0u;
+
+  if (tick_done || beat_done)
+  {
+    FreeMode_CancelEvenBeatStop();
+    KEY_ID_1629 = 0;
+    Stop_AutoBand();
+    LOG_I("pick", "free even-stop done beat=%d tick=%u beatDone=%u",
+          beat, (unsigned)tick_done, (unsigned)beat_done);
+  }
+}
+
 void Stop_AutoBand()
 {  
+  FreeMode_CancelEvenBeatStop();
   AutoBandTop1_Stop();
   for(uint8_t i = 0;i < 16;i++)
   {
@@ -914,10 +1012,10 @@ void TM1629_Handle(uint8_t key)
         PressFlag = 0;
         if(mGuiData[GUI_TAB_INDEX].Current == 2)
         {
-            /* 普通：松手立即结束当前和弦伴奏 */
+            /* 普通：松手对齐到偶拍末再停（拍1→拍2末，拍3→拍4末） */
             KEY_ID_1629 = 0;
             if (StartFlag)
-                Stop_AutoBand();
+                FreeMode_ArmEvenBeatStop();
         }
         else if(mGuiData[GUI_TAB_INDEX].Current == 0)
         {
@@ -940,7 +1038,8 @@ void TM1629_Handle(uint8_t key)
         }
         else if(mGuiData[GUI_TAB_INDEX].Current == 2)
         {
-                /* 普通：按住指板，等待拨片起奏当前和弦 */
+                /* 普通：按住指板；若正在偶拍收束则恢复循环续奏 */
+                FreeMode_ResumePieceLoop();
                 PressFlag = 1;
         }
         uint8_t group = (key - 1) / 3;          /* 1~3→0, 4~6→1, ..., 19~21→6 */
@@ -1637,6 +1736,7 @@ void Read_Cur_Measure()
       (tab == 3 && (last == 0 || last == 2));
 
   Band_TrackPlayTick();
+  FreeMode_PollEvenBeatStop();
 
   /* 尾奏中保持全绿，不刷新和弦走向红灯 */
   if (loop_light_ok && StartFlag && !s_outro_led_all_green)

Global/Global.h

@@ -206,6 +206,8 @@ extern void (*CurrUIProcress)(DisplayTaskMessage_Type xEvent);
 
 
 void Stop_AutoBand();
+/* 普通模式：松手后偶拍收束轮询（由 Read_Cur_Measure 调用） */
+void FreeMode_PollEvenBeatStop(void);
 /* 当前调一级大和弦（把位1 + maj）；开机/进模式/前奏/拨片兜底共用 */
 void Accomp_ApplyDefaultIChord(void);