perf(vd960DBN): OTA RAM 优化 — union 复用块缓冲 + 命令分支数组改 static

MRS 编译 RAM 90.02% (44248/48KB) 逼近历史 .bss 挤栈红线, 减负:
- ota_srv.c: _chunk_buf[256] + _fs_frame[254] 合并为 union (下载/校验与刷写帧
  互斥复用, 省 ~260B static); ota_send_9f 组帧直接用 union 缓冲 (省 254B 栈)
- iot_mqtt_srv.c: 6 个 ota_* 分支 resp[256~400] + ota_data hexbuf[513] 局部栈
  数组改 static (栈峰值 → BSS, 防运行时栈溢出; RAM 总量不变但运行时安全)

验证: gcc 隔离单测 9/9 全过; 语法 0 新增错误

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/iot_mqtt_srv.c

@@ -710,7 +710,7 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_begin") == 0) {
         /* V1.08: 开启 OTA 会话 / 断点续传定位 (Loop MCU 远程 OTA, 先存后刷) */
-        char resp[400];
+        static char resp[400];   /* static: RAM 90% 下防栈峰值 (历史 .bss 挤栈事故) */
         uint32_t size = 0, crc32 = 0;
         char version[16] = {0};
         uint8_t force = 0;
@@ -750,8 +750,8 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_data") == 0) {
         /* V1.08: 分片下发 (256B/片, 单片 CRC32; 重复片幂等, 乱序拒收指示续传) */
-        char resp[400];
+        static char resp[400];
-        char hexbuf[512 + 1];
+        static char hexbuf[512 + 1];   /* 512 hex 最大, static 防栈峰值 */
         const char *hp;
         uint32_t offset = 0, crc32 = 0;
         int rc;
@@ -793,7 +793,7 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_end") == 0) {
         /* V1.08: 结束下载, 全镜像 CRC32 复核 */
-        char resp[300];
+        static char resp[300];
         uint32_t crc32 = 0;
         int rc;
         memset(tmp, 0, sizeof(tmp));
@@ -827,7 +827,7 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_abort") == 0) {
         /* V1.08: 中止会话, 释放暂存 */
-        char resp[256];
+        static char resp[256];
         int rc = ota_cmd_abort();
         snprintf(resp, sizeof(resp),
             "{\"msg_id\":%lu,\"cmd\":\"ota_abort\",\"ts\":%lu,\"code\":%d,\"msg\":\"%s\"}",
@@ -837,7 +837,7 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_flash") == 0) {
         /* V1.08: 触发本地 ISP 刷写 (同步安全检查 → 异步执行) */
-        char resp[300];
+        static char resp[300];
         char slot_buf[8] = {0};
         uint8_t slot = 0, force = 0;
         int rc;
@@ -868,7 +868,7 @@ static void iot_handle_publish(const char *topic, uint8_t *payload, int payload_
 
     } else if (strcmp(cmd_str, "ota_status") == 0) {
         /* V1.08: 查询 OTA 状态 (含刷写进度) */
-        char resp[400];
+        static char resp[400];
         const OtaMeta *m = ota_meta();
         snprintf(resp, sizeof(resp),
             "{\"msg_id\":%lu,\"cmd\":\"ota_status\",\"ts\":%lu,\"code\":0,\"msg\":\"success\","

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/ota_srv.c

@@ -46,9 +46,11 @@ static uint32_t  _fs_block_crc;      /* 当前块 CRC (调试/审计) */
 
 uint8_t g_ota_flash_active = 0;      /* 本地刷写进行中 → uart_srv 把 ACK 交给 ota_srv */
 
-/* 块缓冲 (static: 栈紧张教训) */
+/* 块缓冲 (static: 栈紧张教训; union: 下载片 256B 与 A7 帧 254B 互斥复用, 省 ~260B RAM) */
-static uint8_t _chunk_buf[OTA_CHUNK_SIZE];   /* 下载片缓冲 */
+static union {
-static uint8_t _fs_frame[5 + OTA_FLASH_BLOCK + 1];  /* A7 帧: 9F+SubL+SubH+LEN+CMD+DATA+CHECK */
+    uint8_t chunk[OTA_CHUNK_SIZE];              /* 下载片缓冲 / 校验读缓冲 */
+    uint8_t frame[5 + OTA_FLASH_BLOCK + 1];     /* A7 帧: 9F+SubL+SubH+LEN+CMD+DATA+CHECK */
+} _ota_buf;
 
 /*===========================================================================
  * CRC-32/ISO-HDLC (协议 §4.19.1; 逐位实现, 零查表 RAM)
@@ -275,15 +277,15 @@ int ota_cmd_data(uint32_t offset, uint32_t crc32, const char *hex)
     clen = _meta.size - offset;
     if (clen > OTA_CHUNK_SIZE) clen = OTA_CHUNK_SIZE;
 
-    if (ota_hex_decode(hex, _chunk_buf, clen) != 0) {
+    if (ota_hex_decode(hex, _ota_buf.chunk, clen) != 0) {
         return 1;   /* hex 格式错误 */
     }
-    if (ota_crc32(_chunk_buf, clen) != crc32) {
+    if (ota_crc32(_ota_buf.chunk, clen) != crc32) {
         return 1;   /* 单片 CRC 失败 */
     }
 
     /* 落盘: SPI_Flash_Write 自带"目标区非 0xFF 则读-改-写擦扇区" (256B 页对齐) */
-    SPI_Flash_Write(_chunk_buf, _slot_base + offset, (uint16_t)clen);
+    SPI_Flash_Write(_ota_buf.chunk, _slot_base + offset, (uint16_t)clen);
     _meta.received = offset + clen;
     ota_meta_flush();
     PRINT("OTA: data@%lu crc_ok received=%lu\n",
@@ -313,8 +315,8 @@ int ota_cmd_end(uint32_t crc32)
         while (i < _meta.size) {
             uint32_t n = _meta.size - i;
             if (n > OTA_CHUNK_SIZE) n = OTA_CHUNK_SIZE;
-            SPI_Flash_Read(_chunk_buf, _slot_base + i, (uint16_t)n);
+            SPI_Flash_Read(_ota_buf.chunk, _slot_base + i, (uint16_t)n);
-            total = ota_crc32_update(total, _chunk_buf, n);
+            total = ota_crc32_update(total, _ota_buf.chunk, n);
             i += n;
         }
         total ^= 0xFFFFFFFFu;
@@ -407,18 +409,17 @@ int ota_cmd_flash(uint8_t slot, uint8_t force)
 static void ota_send_9f(uint8_t sub_l, uint8_t sub_h, uint8_t cmd,
                         const uint8_t *data, uint16_t datalen)
 {
-    uint8_t frame[5 + OTA_FLASH_BLOCK + 1];
     uint16_t i;
     uint8_t sum = 0;
-    frame[0] = 0x9F;
+    _ota_buf.frame[0] = 0x9F;
-    frame[1] = sub_l;
+    _ota_buf.frame[1] = sub_l;
-    frame[2] = sub_h;
+    _ota_buf.frame[2] = sub_h;
-    frame[3] = (uint8_t)(1 + datalen);   /* LEN 含 CMD */
+    _ota_buf.frame[3] = (uint8_t)(1 + datalen);   /* LEN 含 CMD */
-    frame[4] = cmd;
+    _ota_buf.frame[4] = cmd;
-    if (data && datalen) memcpy(&frame[5], data, datalen);
+    if (data && datalen) memcpy(&_ota_buf.frame[5], data, datalen);
-    for (i = 1; i < 5 + datalen; i++) sum += frame[i];  /* SubL..DATA */
+    for (i = 1; i < 5 + datalen; i++) sum += _ota_buf.frame[i];  /* SubL..DATA */
-    frame[5 + datalen] = sum;
+    _ota_buf.frame[5 + datalen] = sum;
-    UART2_SendString(frame, (uint16_t)(5 + datalen + 1));
+    UART2_SendString(_ota_buf.frame, (uint16_t)(5 + datalen + 1));
 }
 
 /* 刷写失败收尾: 状态落盘 + event_report 告警 + 恢复 0x7F 模式 */
@@ -566,9 +567,9 @@ void ota_poll(void)
         uint32_t read_off = _fs_sent;
         uint32_t remain = _meta.size - read_off;
         uint16_t datalen = (remain > OTA_FLASH_BLOCK) ? OTA_FLASH_BLOCK : (uint16_t)remain;
-        SPI_Flash_Read(_fs_frame + 5, _slot_base + read_off, datalen);
+        SPI_Flash_Read(_ota_buf.frame + 5, _slot_base + read_off, datalen);
         ota_send_9f((uint8_t)(_fs_sub & 0xFF), (uint8_t)(_fs_sub >> 8), 0xA7,
-                    _fs_frame + 5, datalen);
+                    _ota_buf.frame + 5, datalen);
         _fs = OTA_FLASH_WAIT_ACK;
         _fs_start_ms = now;
         PRINT("OTA: sent A7 sub=%u off=%lu datalen=%u\n",