perf(vd960DBN): RAM 瘦身 — .bss 省 4.8KB, 栈 1.9KB→~6.7KB (2026-08-17)

栈溢出根因确认后 .bss 瘦身四刀:
- net_config.h: ETH_MAX_PACKET_SIZE 1520→768 (MSS=700最大帧758B, 省3.76KB)
- iot_mqtt_srv.c: payload[1400]→800 (loop_data最大~604B, 省600B)
- iot_mqtt_srv.h: IOT_MQTT_SEND_BUF_LEN 1024→800 (_iot_send_buf/resp/buf 同步, 省224B)
- net_srv.c: MAX_MQTTBUF_LEN 1024→800 (512仍不够勿回改, 省224B)

⚠ ETH 768 为 MSS=700 最小安全值; 若现场有大UDP包截断改回1024。
待办: .map 确认 BLE 栈占用; RECE_BUF_LEN/ARP 表可再省; 局部大数组转static。

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/include/iot_mqtt_srv.h

@@ -22,7 +22,7 @@
 #define IOT_MQTT_RECONNECT_MAX_MS  60000     // 最大重连间隔 (指数退避上限)
 #define IOT_MQTT_HEARTBEAT_MS      60000     // 心跳上报周期 (60s)
 #define IOT_MQTT_RECV_BUF_LEN      1024      // 接收缓冲区 (单次交互 ≤1024)
-#define IOT_MQTT_SEND_BUF_LEN      1024      // 发送缓冲区 (单次交互 ≤1024)
+#define IOT_MQTT_SEND_BUF_LEN      800       // 发送缓冲区 (2026-08-17: 1024→800, loop_data~604B+头~30B<800, 省 224B .bss)
 #define IOT_MQTT_TOPIC_MAX_LEN     128       // Topic 最大长度
 
 /*===========================================================================

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/include/net_config.h

@@ -47,6 +47,12 @@ extern "C" {
 
 #define ETH_RXBUFNB                   4    /* Number of MAC received descriptors  */
 
+/* 2026-08-17 RAM 瘦身: ETH_MAX_PACKET_SIZE 1520 → 768.
+   最大 TCP 帧 (MSS=700) = 700+20+20+14+4 = 758B ≤ 768 ✓;
+   停车场景 (TCP JSON/MQTT/SSC UDP 小包) 无 >728B UDP 数据。
+   省 .bss: (1520-768)×(RX 4 + TX 1) = 3.76KB (栈空间 +3.76KB)。
+   若现场出现大 UDP 包截断, 改回 1024 (省 2.48KB)。 */
+#define ETH_MAX_PACKET_SIZE           768
 #ifndef ETH_MAX_PACKET_SIZE
 #define ETH_RX_BUF_SZE                1520  /* MAC receive buffer length, an integer multiple of 4 */
 #define ETH_TX_BUF_SZE                1520  /* MAC send buffer length, an integer multiple of 4 */

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/iot_mqtt_srv.c

@@ -855,7 +855,7 @@ void iot_mqtt_publish_sensor(void) {
        - 用 iot_mqtt_publish() 代替 mqtt_publish(), 发送缓冲隔离
          (event_report→mqttBuf vs loop_data→iot_mqtt_publish::buf[1024])
        - coil_count 边界硬限, 防 0xC0 坏帧致溢出                        */
-    static char payload[1400];
+    static char payload[800];   /* 2026-08-17: 1400→800, loop_data 最大~604B, 省 600B .bss */
     char *p = payload;
     int remaining = sizeof(payload);
     int written;

vd960DBN/BLE/OnlyUpdateApp_Peripheral/APP/net_srv.c

@@ -65,7 +65,7 @@ uint8_t MyBuf[RECE_BUF_LEN];
 
 
 #define         MAX_TMP_BUF_LEN     64
-#define         MAX_MQTTBUF_LEN     1024 //512: loop_data(4通道)≈604B > 512 → 序列化失败发全零垃圾包被broker RST (2026-07-15)
+#define         MAX_MQTTBUF_LEN     800  // 2026-08-17: 1024→800 (loop_data~604B+头<800; 512仍不够勿改回) 省224B .bss
 char mqtt_username[64] = {0};
 char mqtt_password[32] = {0};
 char mqtt_clientid[64] = {0};