test(vd960DBN): SPI写密度模拟实验 + factory写止血 — VDD跌落诊断

- peripheral_main: sim_snap_spi 模拟快照落盘节奏 (20ms 64B页写 + 每64条切扇区擦除+头写)
- cfig_flash: magic不匹配时跳过 factory SPI_Flash_Write, 用内存默认值继续
  (SPI写触发硬件复位死循环止血: 参数区0x00写也崩, RST=0x00000000)
- 诊断修正: CH32V208GBU6 QFN28 无 NRST 引脚, 共线假设作废;
  SPI写/擦除→电流尖峰→VDD跌落→内部POR/PDR(2.4V)复位;
  BLE射频+SPI电流叠加是头号嫌疑

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/peripheral_main.c

@@ -217,6 +217,75 @@ void key_event_srv(void){
 }
 
 
+/*********************************************************************
+ * @fn      sim_snap_spi
+ *
+ * @brief   实验(2026-08-13 第一步): 模拟快照区 SPI 写密度
+ *
+ *          当前固件: snap_init 已 #if 0 跳过 (纯读基座, 日志读写正常)。
+ *          本函数恢复快照落盘的写节奏, 隔离"SPI 写频率" vs "快照逻辑 bug":
+ *          - 每 20ms: 64B 页写 (SPI_Flash_Write_NoCheck, 模拟 snap_write_raw)
+ *          - 每 64 条: 切扇区序列 (读首条 magic + 擦除 45ms +
+ *                      头区 SPI_Flash_Write 读-改-写整扇区, 模拟 snap_flush_head)
+ *          复现复位 → SPI 高频写触发硬件问题 (PA7/NRST 共线怀疑坐实);
+ *          不复现 → 快照区有具体逻辑 bug, 转向代码审查。
+ *          注意: 会覆盖快照区旧数据, 恢复快照功能前需 snap_clear。
+ *
+ * @return  none
+ */
+#define SIM_SNAP_HEAD_BASE  0x110000UL
+#define SIM_SNAP_DATA_BASE  0x111000UL
+#define SIM_SNAP_DATA_SIZE  (4096UL * 751UL)   /* 与 snapshot.c 数据扇区数一致 */
+static uint32_t _sim_snap_wr   = SIM_SNAP_DATA_BASE;
+static uint32_t _sim_snap_cnt  = 0;
+static uint32_t _sim_snap_last = 0;
+void sim_snap_spi(void)
+{
+    uint32_t _now = mstick();
+
+    if ((uint32_t)(_now - _sim_snap_last) < 20) return;   /* 20ms 节拍 = 50Hz 帧率 */
+    _sim_snap_last = _now;
+
+    /* 切扇区: 每 64 条 (4096/64) 一次, 与 snap_write_raw 同节奏 */
+    if (_sim_snap_cnt > 0 && (_sim_snap_cnt & 63) == 0)
+    {
+        uint8_t _r[64];
+        uint8_t _h[32];
+
+        /* 1) snap_sector_has_data: 读目标扇区首条 magic */
+        SPI_Flash_Read(_r, _sim_snap_wr, 64);
+
+        /* 2) SPI_Flash_Erase_Sector (~45ms) */
+        SPI_Flash_Erase_Sector(_sim_snap_wr / 4096);
+
+        /* 3) snap_flush_head: 头区读-改-写 (SPI_Flash_Write 内部
+              读4096 + 擦 + 写回4096, ~100ms) */
+        memset(_h, 0xFF, sizeof(_h));
+        _h[0] = 'S'; _h[1] = 'N'; _h[2] = 'P'; _h[3] = 'M';
+        _h[8]  = (uint8_t)(_sim_snap_cnt & 0xFF);
+        _h[9]  = (uint8_t)((_sim_snap_cnt >> 8) & 0xFF);
+        _h[10] = (uint8_t)((_sim_snap_cnt >> 16) & 0xFF);
+        _h[11] = (uint8_t)((_sim_snap_cnt >> 24) & 0xFF);
+        SPI_Flash_Write(_h, SIM_SNAP_HEAD_BASE, 32);
+    }
+
+    /* 模拟 snap_write_raw: 64B 页写 */
+    {
+        static uint8_t _b[64];
+        uint8_t _i;
+        for (_i = 0; _i < 64; _i++) _b[_i] = (uint8_t)(_sim_snap_cnt + _i);
+        _b[0] = 'S'; _b[1] = 'N'; _b[2] = 'P'; _b[3] = 'M';
+        SPI_Flash_Write_NoCheck(_b, _sim_snap_wr, 64);
+        _sim_snap_wr += 64;
+        if (_sim_snap_wr >= SIM_SNAP_DATA_BASE + SIM_SNAP_DATA_SIZE)
+            _sim_snap_wr = SIM_SNAP_DATA_BASE;
+        _sim_snap_cnt++;
+        if ((_sim_snap_cnt & 0x3F) == 0)
+            PRINT("SIM: cnt=%lu wr=0x%08lx\n",
+                  (unsigned long)_sim_snap_cnt, (unsigned long)_sim_snap_wr);
+    }
+}
+
 /*********************************************************************
  * @fn      Main_Circulation
  *
@@ -269,6 +338,7 @@ void Main_Circulation(void)
 
         uart_srv();
         snap_flush();   /* 快照落盘: 无条件挂主循环 (原在 iot_enable 分支, TCP 模式不落盘) */
+        sim_snap_spi(); /* 实验第一步(2026-08-13): 模拟快照区 SPI 写密度, 定位复位触发源 */
 
         poll_dbn_ble();