docs: record v1.1.0 low-RAM TCP backpressure design

Document the AT+BAUD flow in the debug guide, including U0/U1 data-port mapping and the save/reset behavior required for USART2/USART3 baud changes.

.gitignore

@@ -44,3 +44,9 @@ Desktop.ini
 
 # Local packet captures
 WiresharkLog/
+
+# Local build/session artifacts
+.embeddedskills/
+uv4_stdout.txt
+MDK-ARM/EventRecorderStub.scvd
+MDK-ARM/build_capture.txt

AT固件使用手册.md

@@ -143,6 +143,12 @@ UART 记号约定：
 - `U0 = USART2`
 - `U1 = USART3`
 
+### 7.4 BAUD 默认值
+
+```text
+BAUD = U0,115200 / U1,115200
+```
+
 ## 8. AT 命令定义
 
 ### 8.1 测试设备在线
@@ -239,7 +245,45 @@ OK
 
 当MAC设置为全0时，固件将使用硬件MAC地址，此时通过AT+?查询到的MAC地址即为当前生效的硬件MAC地址。
 
-### 8.5 LINK 类命令
+### 8.5 BAUD 类命令
+
+#### 查询 UART 波特率
+
+```text
+AT+BAUD?\r\n
+```
+
+返回示例：
+
+```text
++BAUD:U0=115200,U1=115200
+OK
+```
+
+#### 设置 UART 波特率
+
+```text
+AT+BAUD=U0,115200\r\n
+AT+BAUD=U1,38400\r\n
+```
+
+字段顺序：
+
+```text
+UART,BAUDRATE
+```
+
+字段说明：
+
+- `UART`：`U0/U1`
+- `BAUDRATE`：范围 `1200~921600`
+
+说明：
+
+- 该命令只更新当前运行配置记录，不会立即重初始化 `USART2/USART3`
+- 执行 `AT+SAVE` 后再执行 `AT+RESET`，重启时按保存值生效
+
+### 8.6 LINK 类命令
 
 #### 设置单条 LINK 记录
 
@@ -382,6 +426,28 @@ AT+RESET\r\n
 1. `AT+SAVE\r\n`
 2. `AT+RESET\r\n`
 
+### 12.3 MUX 模式数据口有丢包
+
+若 `MUX=1` 下出现“主机侧已发送，但设备对端收到数量明显偏少”的现象，优先按以下顺序检查：
+
+1. 固件版本是否已经包含 `2026-04-18` 的 MUX 丢包修复。
+2. MUX 帧是否完整，尤其是：
+   - `SYNC=0x7E`
+   - `LEN_H/LEN_L`
+   - `SRCID`
+   - `DSTMASK`
+   - `TAIL=0x7F`
+3. 上位机发送方式是否把一帧拆成多个不连续小片段，或在帧间插入无效字节。
+4. TCP 对端是否出现拥塞、窗口缩小或应用层不及时取数，导致发送路径出现背压。
+5. RTT 中是否存在链路错误、发送失败或持续重连现象。
+
+当前版本的修复点如下：
+
+1. MUX 解析器改为在整帧完整到齐前不推进 UART RX ring 读指针，避免半帧被破坏性消费。
+2. TCP 发送路径与 UART 写入路径不再把背压和短写静默视为成功，便于及早暴露链路承载问题。
+
+现场回归结果：在修复后的固件中，MUX 模式持续发送 `670` 包，接收端 `670` 包全部到达，`0` 丢包。
+
 ## 13. 相关文件
 
 - AT 命令实现：[config.c](/D:/code/STM32Project/TCP2UART/App/config.c)

App/config.c

@@ -365,8 +365,8 @@ static at_result_t handle_summary_query(char *response, uint16_t max_len)
              g_config.links[2].enabled, g_config.links[2].local_port, rip_str[2], g_config.links[2].remote_port, link_uart_to_str(g_config.links[2].uart),
              g_config.links[3].enabled, g_config.links[3].local_port, rip_str[3], g_config.links[3].remote_port, link_uart_to_str(g_config.links[3].uart),
              g_config.mux_mode,
-             g_config.uart_baudrate[0],
+             (unsigned long)g_config.uart_baudrate[0],
-             g_config.uart_baudrate[1]);
+             (unsigned long)g_config.uart_baudrate[1]);
 
     return AT_OK;
 }
@@ -386,6 +386,16 @@ static at_result_t handle_net_query(char *response, uint16_t max_len)
     return AT_OK;
 }
 
+static at_result_t handle_baud_query(char *response, uint16_t max_len)
+{
+    snprintf(response,
+             max_len,
+             "+BAUD:U0=%lu,U1=%lu\r\nOK\r\n",
+             (unsigned long)g_config.uart_baudrate[0],
+             (unsigned long)g_config.uart_baudrate[1]);
+    return AT_OK;
+}
+
 static at_result_t handle_link_query(uint32_t index, char *response, uint16_t max_len)
 {
     char rip_str[16];
@@ -556,6 +566,38 @@ at_result_t config_process_at_cmd(const char *cmd, char *response, uint16_t max_
         snprintf(response, max_len, "OK\r\n");
         return AT_NEED_REBOOT;
     }
+    if (equals_ignore_case(p, "BAUD?")) {
+        return handle_baud_query(response, max_len);
+    }
+    if (parse_command_with_value(p, "BAUD", &value)) {
+        char value_copy[32];
+        char *cursor;
+        char *token;
+        uint8_t uart;
+        uint32_t baudrate;
+
+        strncpy(value_copy, value, sizeof(value_copy) - 1u);
+        value_copy[sizeof(value_copy) - 1u] = '\0';
+        cursor = value_copy;
+
+        token = config_next_token(&cursor);
+        if (token == NULL || parse_link_uart(token, &uart) != 0) {
+            snprintf(response, max_len, "ERROR: Invalid route field\r\n");
+            return AT_INVALID_PARAM;
+        }
+        token = config_next_token(&cursor);
+        if (token == NULL || parse_u32_value(token, 1200u, 921600u, &baudrate) != 0) {
+            snprintf(response, max_len, "ERROR: Invalid baudrate\r\n");
+            return AT_INVALID_PARAM;
+        }
+        if (config_next_token(&cursor) != NULL) {
+            snprintf(response, max_len, "ERROR: Invalid value\r\n");
+            return AT_INVALID_PARAM;
+        }
+
+        g_config.uart_baudrate[uart] = baudrate;
+        return handle_baud_query(response, max_len) == AT_OK ? AT_NEED_REBOOT : AT_ERROR;
+    }
     if (equals_ignore_case(p, "NET?")) {
         return handle_net_query(response, max_len);
     }

App/tcp_client.c

@@ -17,6 +17,8 @@ typedef struct {
     uint8_t rx_ring[TCP_CLIENT_RX_BUFFER_SIZE];
     uint16_t rx_head;
     uint16_t rx_tail;
+    struct pbuf *hold_pbuf;
+    uint16_t hold_offset;
     uint32_t next_retry_ms;
     uint8_t index;
     tcp_client_instance_config_t config;
@@ -30,10 +32,65 @@ static uint16_t ring_free(uint16_t head, uint16_t tail, uint16_t size)
     return (head >= tail) ? (uint16_t)(size - head + tail - 1u) : (uint16_t)(tail - head - 1u);
 }
 
+static uint16_t ring_used(uint16_t head, uint16_t tail, uint16_t size)
+{
+    return (head >= tail) ? (uint16_t)(head - tail) : (uint16_t)(size - tail + head);
+}
+
+static void tcp_client_reset_rx_state(tcp_client_ctx_t *ctx)
+{
+    if (ctx == NULL) {
+        return;
+    }
+    if (ctx->hold_pbuf != NULL) {
+        pbuf_free(ctx->hold_pbuf);
+        ctx->hold_pbuf = NULL;
+    }
+    ctx->hold_offset = 0u;
+    ctx->rx_head = 0u;
+    ctx->rx_tail = 0u;
+}
+
+static void tcp_client_fill_ring_from_pbuf(tcp_client_ctx_t *ctx)
+{
+    struct pbuf *q;
+    uint16_t offset;
+
+    if (ctx == NULL || ctx->hold_pbuf == NULL) {
+        return;
+    }
+
+    q = ctx->hold_pbuf;
+    offset = ctx->hold_offset;
+    while (q != NULL && offset >= q->len) {
+        offset = (uint16_t)(offset - q->len);
+        q = q->next;
+    }
+
+    while (q != NULL) {
+        const uint8_t *src = (const uint8_t *)q->payload;
+        for (uint16_t i = offset; i < q->len; ++i) {
+            if (ring_free(ctx->rx_head, ctx->rx_tail, TCP_CLIENT_RX_BUFFER_SIZE) == 0u) {
+                ctx->hold_offset = (uint16_t)(ctx->hold_offset + i - offset);
+                return;
+            }
+            ctx->rx_ring[ctx->rx_head] = src[i];
+            ctx->rx_head = (uint16_t)((ctx->rx_head + 1u) % TCP_CLIENT_RX_BUFFER_SIZE);
+            ctx->status.rx_bytes++;
+        }
+        ctx->hold_offset = (uint16_t)(ctx->hold_offset + q->len - offset);
+        offset = 0u;
+        q = q->next;
+    }
+
+    pbuf_free(ctx->hold_pbuf);
+    ctx->hold_pbuf = NULL;
+    ctx->hold_offset = 0u;
+}
+
 static err_t tcp_client_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
 {
     tcp_client_ctx_t *ctx = (tcp_client_ctx_t *)arg;
-    struct pbuf *q;
 
     if (ctx == NULL) {
         if (p != NULL) {
@@ -59,21 +116,16 @@ static err_t tcp_client_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p,
         return ERR_ABRT;
     }
 
-    for (q = p; q != NULL; q = q->next) {
+    if (ctx->hold_pbuf != NULL) {
-        const uint8_t *src = (const uint8_t *)q->payload;
-        for (uint16_t i = 0; i < q->len; ++i) {
-            if (ring_free(ctx->rx_head, ctx->rx_tail, TCP_CLIENT_RX_BUFFER_SIZE) == 0u) {
         ctx->status.errors++;
-                break;
+        return ERR_MEM;
-            }
-            ctx->rx_ring[ctx->rx_head] = src[i];
-            ctx->rx_head = (uint16_t)((ctx->rx_head + 1u) % TCP_CLIENT_RX_BUFFER_SIZE);
-            ctx->status.rx_bytes++;
-        }
     }
 
-    tcp_recved(pcb, p->tot_len);
+    pbuf_ref(p);
+    ctx->hold_pbuf = p;
+    ctx->hold_offset = 0u;
     pbuf_free(p);
+    tcp_client_fill_ring_from_pbuf(ctx);
     return ERR_OK;
 }
 
@@ -93,6 +145,7 @@ static void tcp_client_on_err(void *arg, err_t err)
     if (ctx == NULL) {
         return;
     }
+    tcp_client_reset_rx_state(ctx);
     ctx->pcb = NULL;
     ctx->status.state = TCP_CLIENT_STATE_DISCONNECTED;
     ctx->status.errors++;
@@ -213,6 +266,7 @@ int tcp_client_disconnect(uint8_t instance)
     }
     ctx = &g_clients[instance];
     if (ctx->pcb != NULL) {
+        tcp_client_reset_rx_state(ctx);
         tcp_arg(ctx->pcb, NULL);
         tcp_recv(ctx->pcb, NULL);
         tcp_sent(ctx->pcb, NULL);
@@ -221,8 +275,7 @@ int tcp_client_disconnect(uint8_t instance)
         ctx->pcb = NULL;
     }
     ctx->status.state = TCP_CLIENT_STATE_DISCONNECTED;
-    ctx->rx_head = 0u;
+    tcp_client_reset_rx_state(ctx);
-    ctx->rx_tail = 0u;
     return 0;
 }
 
@@ -239,14 +292,23 @@ int tcp_client_send(uint8_t instance, const uint8_t *data, uint16_t len)
         return -1;
     }
     if (tcp_sndbuf(ctx->pcb) < len) {
+        ctx->status.errors++;
         return 0;
     }
     err = tcp_write(ctx->pcb, data, len, TCP_WRITE_FLAG_COPY);
+    if (err == ERR_MEM) {
+        ctx->status.errors++;
+        return 0;
+    }
     if (err != ERR_OK) {
         ctx->status.errors++;
         return -1;
     }
     err = tcp_output(ctx->pcb);
+    if (err == ERR_MEM) {
+        ctx->status.errors++;
+        return 0;
+    }
     if (err != ERR_OK) {
         ctx->status.errors++;
         return -1;
@@ -263,13 +325,66 @@ int tcp_client_recv(uint8_t instance, uint8_t *data, uint16_t max_len)
         return -1;
     }
     ctx = &g_clients[instance];
+    tcp_client_fill_ring_from_pbuf(ctx);
     while (copied < max_len && ctx->rx_tail != ctx->rx_head) {
         data[copied++] = ctx->rx_ring[ctx->rx_tail];
         ctx->rx_tail = (uint16_t)((ctx->rx_tail + 1u) % TCP_CLIENT_RX_BUFFER_SIZE);
     }
+    if (copied > 0u && ctx->pcb != NULL) {
+        tcp_recved(ctx->pcb, copied);
+    }
     return (int)copied;
 }
 
+uint16_t tcp_client_rx_available(uint8_t instance)
+{
+    if (instance >= TCP_CLIENT_INSTANCE_COUNT) {
+        return 0u;
+    }
+    tcp_client_fill_ring_from_pbuf(&g_clients[instance]);
+    return ring_used(g_clients[instance].rx_head, g_clients[instance].rx_tail, TCP_CLIENT_RX_BUFFER_SIZE);
+}
+
+uint16_t tcp_client_peek(uint8_t instance, uint8_t *data, uint16_t max_len)
+{
+    uint16_t copied = 0u;
+    uint16_t tail;
+    tcp_client_ctx_t *ctx;
+
+    if (instance >= TCP_CLIENT_INSTANCE_COUNT || data == NULL || max_len == 0u) {
+        return 0u;
+    }
+
+    ctx = &g_clients[instance];
+    tcp_client_fill_ring_from_pbuf(ctx);
+    tail = ctx->rx_tail;
+    while (copied < max_len && tail != ctx->rx_head) {
+        data[copied++] = ctx->rx_ring[tail];
+        tail = (uint16_t)((tail + 1u) % TCP_CLIENT_RX_BUFFER_SIZE);
+    }
+    return copied;
+}
+
+void tcp_client_drop(uint8_t instance, uint16_t len)
+{
+    tcp_client_ctx_t *ctx;
+    uint16_t dropped = 0u;
+
+    if (instance >= TCP_CLIENT_INSTANCE_COUNT || len == 0u) {
+        return;
+    }
+
+    ctx = &g_clients[instance];
+    while (dropped < len && ctx->rx_tail != ctx->rx_head) {
+        ctx->rx_tail = (uint16_t)((ctx->rx_tail + 1u) % TCP_CLIENT_RX_BUFFER_SIZE);
+        dropped++;
+    }
+    if (dropped > 0u && ctx->pcb != NULL) {
+        tcp_recved(ctx->pcb, dropped);
+    }
+    tcp_client_fill_ring_from_pbuf(ctx);
+}
+
 bool tcp_client_is_connected(uint8_t instance)
 {
     return (instance < TCP_CLIENT_INSTANCE_COUNT) &&
@@ -290,6 +405,7 @@ void tcp_client_poll(void)
 
     for (uint8_t i = 0; i < TCP_CLIENT_INSTANCE_COUNT; ++i) {
         tcp_client_ctx_t *ctx = &g_clients[i];
+        tcp_client_fill_ring_from_pbuf(ctx);
         if (!ctx->config.enabled || !ctx->config.auto_reconnect || tcp_client_is_connected(i)) {
             continue;
         }

App/tcp_client.h

@@ -14,7 +14,7 @@ extern "C" {
 #endif
 
 #define TCP_CLIENT_INSTANCE_COUNT      2u
-#define TCP_CLIENT_RX_BUFFER_SIZE      512u
+#define TCP_CLIENT_RX_BUFFER_SIZE      480u
 #define TCP_CLIENT_RECONNECT_DELAY_MS  3000u
 
 typedef enum {
@@ -48,6 +48,9 @@ int tcp_client_connect(uint8_t instance);
 int tcp_client_disconnect(uint8_t instance);
 int tcp_client_send(uint8_t instance, const uint8_t *data, uint16_t len);
 int tcp_client_recv(uint8_t instance, uint8_t *data, uint16_t max_len);
+uint16_t tcp_client_rx_available(uint8_t instance);
+uint16_t tcp_client_peek(uint8_t instance, uint8_t *data, uint16_t max_len);
+void tcp_client_drop(uint8_t instance, uint16_t len);
 bool tcp_client_is_connected(uint8_t instance);
 void tcp_client_get_status(uint8_t instance, tcp_client_status_t *status);
 void tcp_client_poll(void);

App/tcp_server.c

@@ -18,6 +18,8 @@ typedef struct {
     uint8_t rx_ring[TCP_SERVER_RX_BUFFER_SIZE];
     uint16_t rx_head;
     uint16_t rx_tail;
+    struct pbuf *hold_pbuf;
+    uint16_t hold_offset;
     uint8_t index;
     tcp_server_instance_config_t config;
     tcp_server_status_t status;
@@ -30,10 +32,65 @@ static uint16_t ring_free(uint16_t head, uint16_t tail, uint16_t size)
     return (head >= tail) ? (uint16_t)(size - head + tail - 1u) : (uint16_t)(tail - head - 1u);
 }
 
+static uint16_t ring_used(uint16_t head, uint16_t tail, uint16_t size)
+{
+    return (head >= tail) ? (uint16_t)(head - tail) : (uint16_t)(size - tail + head);
+}
+
+static void tcp_server_reset_rx_state(tcp_server_ctx_t *ctx)
+{
+    if (ctx == NULL) {
+        return;
+    }
+    if (ctx->hold_pbuf != NULL) {
+        pbuf_free(ctx->hold_pbuf);
+        ctx->hold_pbuf = NULL;
+    }
+    ctx->hold_offset = 0u;
+    ctx->rx_head = 0u;
+    ctx->rx_tail = 0u;
+}
+
+static void tcp_server_fill_ring_from_pbuf(tcp_server_ctx_t *ctx)
+{
+    struct pbuf *q;
+    uint16_t offset;
+
+    if (ctx == NULL || ctx->hold_pbuf == NULL) {
+        return;
+    }
+
+    q = ctx->hold_pbuf;
+    offset = ctx->hold_offset;
+    while (q != NULL && offset >= q->len) {
+        offset = (uint16_t)(offset - q->len);
+        q = q->next;
+    }
+
+    while (q != NULL) {
+        const uint8_t *src = (const uint8_t *)q->payload;
+        for (uint16_t i = offset; i < q->len; ++i) {
+            if (ring_free(ctx->rx_head, ctx->rx_tail, TCP_SERVER_RX_BUFFER_SIZE) == 0u) {
+                ctx->hold_offset = (uint16_t)(ctx->hold_offset + i - offset);
+                return;
+            }
+            ctx->rx_ring[ctx->rx_head] = src[i];
+            ctx->rx_head = (uint16_t)((ctx->rx_head + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
+            ctx->status.rx_bytes++;
+        }
+        ctx->hold_offset = (uint16_t)(ctx->hold_offset + q->len - offset);
+        offset = 0u;
+        q = q->next;
+    }
+
+    pbuf_free(ctx->hold_pbuf);
+    ctx->hold_pbuf = NULL;
+    ctx->hold_offset = 0u;
+}
+
 static err_t tcp_server_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
 {
     tcp_server_ctx_t *ctx = (tcp_server_ctx_t *)arg;
-    struct pbuf *q;
 
     if (ctx == NULL) {
         if (p != NULL) {
@@ -58,21 +115,16 @@ static err_t tcp_server_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p,
         return ERR_ABRT;
     }
 
-    for (q = p; q != NULL; q = q->next) {
+    if (ctx->hold_pbuf != NULL) {
-        const uint8_t *src = (const uint8_t *)q->payload;
-        for (uint16_t i = 0; i < q->len; ++i) {
-            if (ring_free(ctx->rx_head, ctx->rx_tail, TCP_SERVER_RX_BUFFER_SIZE) == 0u) {
         ctx->status.errors++;
-                break;
+        return ERR_MEM;
-            }
-            ctx->rx_ring[ctx->rx_head] = src[i];
-            ctx->rx_head = (uint16_t)((ctx->rx_head + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
-            ctx->status.rx_bytes++;
-        }
     }
 
-    tcp_recved(pcb, p->tot_len);
+    pbuf_ref(p);
+    ctx->hold_pbuf = p;
+    ctx->hold_offset = 0u;
     pbuf_free(p);
+    tcp_server_fill_ring_from_pbuf(ctx);
     return ERR_OK;
 }
 
@@ -92,6 +144,7 @@ static void tcp_server_on_err(void *arg, err_t err)
     if (ctx == NULL) {
         return;
     }
+    tcp_server_reset_rx_state(ctx);
     ctx->client_pcb = NULL;
     ctx->status.state = ctx->config.enabled ? TCP_SERVER_STATE_LISTENING : TCP_SERVER_STATE_IDLE;
     ctx->status.errors++;
@@ -193,6 +246,7 @@ int tcp_server_stop(uint8_t instance)
     ctx = &g_servers[instance];
 
     if (ctx->client_pcb != NULL) {
+        tcp_server_reset_rx_state(ctx);
         tcp_arg(ctx->client_pcb, NULL);
         tcp_recv(ctx->client_pcb, NULL);
         tcp_sent(ctx->client_pcb, NULL);
@@ -210,8 +264,7 @@ int tcp_server_stop(uint8_t instance)
     }
 
     ctx->status.state = TCP_SERVER_STATE_IDLE;
-    ctx->rx_head = 0u;
+    tcp_server_reset_rx_state(ctx);
-    ctx->rx_tail = 0u;
     return 0;
 }
 
@@ -228,15 +281,24 @@ int tcp_server_send(uint8_t instance, const uint8_t *data, uint16_t len)
         return -1;
     }
     if (tcp_sndbuf(ctx->client_pcb) < len) {
+        ctx->status.errors++;
         return 0;
     }
 
     err = tcp_write(ctx->client_pcb, data, len, TCP_WRITE_FLAG_COPY);
+    if (err == ERR_MEM) {
+        ctx->status.errors++;
+        return 0;
+    }
     if (err != ERR_OK) {
         ctx->status.errors++;
         return -1;
     }
     err = tcp_output(ctx->client_pcb);
+    if (err == ERR_MEM) {
+        ctx->status.errors++;
+        return 0;
+    }
     if (err != ERR_OK) {
         ctx->status.errors++;
         return -1;
@@ -253,13 +315,66 @@ int tcp_server_recv(uint8_t instance, uint8_t *data, uint16_t max_len)
         return -1;
     }
     ctx = &g_servers[instance];
+    tcp_server_fill_ring_from_pbuf(ctx);
     while (copied < max_len && ctx->rx_tail != ctx->rx_head) {
         data[copied++] = ctx->rx_ring[ctx->rx_tail];
         ctx->rx_tail = (uint16_t)((ctx->rx_tail + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
     }
+    if (copied > 0u && ctx->client_pcb != NULL) {
+        tcp_recved(ctx->client_pcb, copied);
+    }
     return (int)copied;
 }
 
+uint16_t tcp_server_rx_available(uint8_t instance)
+{
+    if (instance >= TCP_SERVER_INSTANCE_COUNT) {
+        return 0u;
+    }
+    tcp_server_fill_ring_from_pbuf(&g_servers[instance]);
+    return ring_used(g_servers[instance].rx_head, g_servers[instance].rx_tail, TCP_SERVER_RX_BUFFER_SIZE);
+}
+
+uint16_t tcp_server_peek(uint8_t instance, uint8_t *data, uint16_t max_len)
+{
+    uint16_t copied = 0u;
+    uint16_t tail;
+    tcp_server_ctx_t *ctx;
+
+    if (instance >= TCP_SERVER_INSTANCE_COUNT || data == NULL || max_len == 0u) {
+        return 0u;
+    }
+
+    ctx = &g_servers[instance];
+    tcp_server_fill_ring_from_pbuf(ctx);
+    tail = ctx->rx_tail;
+    while (copied < max_len && tail != ctx->rx_head) {
+        data[copied++] = ctx->rx_ring[tail];
+        tail = (uint16_t)((tail + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
+    }
+    return copied;
+}
+
+void tcp_server_drop(uint8_t instance, uint16_t len)
+{
+    tcp_server_ctx_t *ctx;
+    uint16_t dropped = 0u;
+
+    if (instance >= TCP_SERVER_INSTANCE_COUNT || len == 0u) {
+        return;
+    }
+
+    ctx = &g_servers[instance];
+    while (dropped < len && ctx->rx_tail != ctx->rx_head) {
+        ctx->rx_tail = (uint16_t)((ctx->rx_tail + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
+        dropped++;
+    }
+    if (dropped > 0u && ctx->client_pcb != NULL) {
+        tcp_recved(ctx->client_pcb, dropped);
+    }
+    tcp_server_fill_ring_from_pbuf(ctx);
+}
+
 bool tcp_server_is_connected(uint8_t instance)
 {
     return (instance < TCP_SERVER_INSTANCE_COUNT) && (g_servers[instance].client_pcb != NULL);
@@ -271,3 +386,10 @@ void tcp_server_get_status(uint8_t instance, tcp_server_status_t *status)
         *status = g_servers[instance].status;
     }
 }
+
+void tcp_server_poll(void)
+{
+    for (uint8_t i = 0; i < TCP_SERVER_INSTANCE_COUNT; ++i) {
+        tcp_server_fill_ring_from_pbuf(&g_servers[i]);
+    }
+}

App/tcp_server.h

@@ -14,7 +14,7 @@ extern "C" {
 #endif
 
 #define TCP_SERVER_INSTANCE_COUNT    2u
-#define TCP_SERVER_RX_BUFFER_SIZE    512u
+#define TCP_SERVER_RX_BUFFER_SIZE    480u
 
 typedef enum {
     TCP_SERVER_STATE_IDLE = 0,
@@ -42,8 +42,12 @@ int tcp_server_start(uint8_t instance);
 int tcp_server_stop(uint8_t instance);
 int tcp_server_send(uint8_t instance, const uint8_t *data, uint16_t len);
 int tcp_server_recv(uint8_t instance, uint8_t *data, uint16_t max_len);
+uint16_t tcp_server_rx_available(uint8_t instance);
+uint16_t tcp_server_peek(uint8_t instance, uint8_t *data, uint16_t max_len);
+void tcp_server_drop(uint8_t instance, uint16_t len);
 bool tcp_server_is_connected(uint8_t instance);
 void tcp_server_get_status(uint8_t instance, tcp_server_status_t *status);
+void tcp_server_poll(void);
 
 #ifdef __cplusplus
 }

App/uart_trans.c

@@ -43,6 +43,52 @@ static uint16_t ring_free(uint16_t head, uint16_t tail, uint16_t size)
     return (uint16_t)(size - ring_used(head, tail, size) - 1u);
 }
 
+static bool ring_peek_byte(const uart_channel_ctx_t *ctx, uint16_t offset, uint8_t *out)
+{
+    uint16_t head;
+    uint16_t tail;
+
+    if (ctx == NULL || out == NULL) {
+        return false;
+    }
+
+    head = ctx->rx_head;
+    tail = ctx->rx_tail;
+    if (offset >= ring_used(head, tail, UART_RX_RING_BUFFER_SIZE)) {
+        return false;
+    }
+
+    *out = ctx->rx_ring[(tail + offset) % UART_RX_RING_BUFFER_SIZE];
+    return true;
+}
+
+static bool ring_peek_span(const uart_channel_ctx_t *ctx, uint16_t offset, uint8_t *data, uint16_t len)
+{
+    if (ctx == NULL || data == NULL) {
+        return false;
+    }
+
+    for (uint16_t i = 0u; i < len; ++i) {
+        if (!ring_peek_byte(ctx, (uint16_t)(offset + i), &data[i])) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static void ring_drop_bytes(uart_channel_ctx_t *ctx, uint16_t len)
+{
+    if (ctx == NULL) {
+        return;
+    }
+
+    while (len > 0u && ctx->rx_tail != ctx->rx_head) {
+        ctx->rx_tail = (uint16_t)((ctx->rx_tail + 1u) % UART_RX_RING_BUFFER_SIZE);
+        --len;
+    }
+}
+
 static int apply_uart_config(uart_channel_t channel)
 {
     uart_channel_ctx_t *ctx = &g_channels[channel];
@@ -235,6 +281,14 @@ uint16_t uart_trans_write(uart_channel_t channel, const uint8_t *data, uint16_t
     return written;
 }
 
+uint16_t uart_trans_tx_free(uart_channel_t channel)
+{
+    if (channel >= UART_CHANNEL_MAX) {
+        return 0u;
+    }
+    return ring_free(g_channels[channel].tx_head, g_channels[channel].tx_tail, UART_TX_RING_BUFFER_SIZE);
+}
+
 void uart_trans_get_stats(uart_channel_t channel, uart_stats_t *stats)
 {
     if (channel < UART_CHANNEL_MAX && stats != NULL) {
@@ -297,64 +351,88 @@ void uart_trans_tx_cplt_handler(uart_channel_t channel)
 
 bool uart_mux_try_extract_frame(uart_channel_t channel, uart_mux_frame_t *frame)
 {
-    uint8_t sync_byte;
+    uart_channel_ctx_t *ctx;
     uint8_t header[4];
+    uint8_t tail_byte;
     uint16_t available;
     uint16_t payload_len;
+    uint16_t sync_offset;
+    uint16_t total_len;
 
     if (channel >= UART_CHANNEL_MAX || frame == NULL) {
         return false;
     }
 
+    ctx = &g_channels[channel];
+
+    for (;;) {
         available = uart_trans_rx_available(channel);
         if (available < 6u) {
             return false;
         }
 
-    /* Scan for SYNC byte (0x7E) — discard non-matching bytes one at a time */
+        sync_offset = available;
-    if (uart_trans_read(channel, &sync_byte, 1u) != 1u) {
+        for (uint16_t i = 0u; i < available; ++i) {
+            uint8_t byte = 0u;
+            if (!ring_peek_byte(ctx, i, &byte)) {
                 return false;
             }
-    if (sync_byte != UART_MUX_SYNC) {
+            if (byte == UART_MUX_SYNC) {
+                sync_offset = i;
+                break;
+            }
+        }
+
+        if (sync_offset == available) {
+            ring_drop_bytes(ctx, available);
             return false;
         }
 
-    /* Need at least: 2(len) + 1(src) + 1(dst) + payload + 1(tail) = 5 + payload */
+        if (sync_offset > 0u) {
-    available = uart_trans_rx_available(channel);
+            ring_drop_bytes(ctx, sync_offset);
-    if (available < 4u) {
+            available = (uint16_t)(available - sync_offset);
+        }
+
+        if (available < 6u) {
             return false;
         }
 
-    if (uart_trans_read(channel, header, sizeof(header)) != sizeof(header)) {
+        if (!ring_peek_span(ctx, 1u, header, sizeof(header))) {
             return false;
         }
 
         payload_len = (uint16_t)(((uint16_t)header[0] << 8) | header[1]);
         if (payload_len > sizeof(frame->payload)) {
+            ring_drop_bytes(ctx, 1u);
+            continue;
+        }
+
+        total_len = (uint16_t)(payload_len + 6u);
+        if (available < total_len) {
             return false;
         }
-    if (uart_trans_rx_available(channel) < (uint16_t)(payload_len + 1u)) {
+
+        if (!ring_peek_byte(ctx, (uint16_t)(total_len - 1u), &tail_byte)) {
             return false;
         }
+        if (tail_byte != UART_MUX_TAIL) {
+            ring_drop_bytes(ctx, 1u);
+            continue;
+        }
 
         frame->src_id = header[2];
         frame->dst_mask = header[3];
         frame->payload_len = payload_len;
         if (payload_len > 0u) {
-        if (uart_trans_read(channel, frame->payload, payload_len) != payload_len) {
+            if (!ring_peek_span(ctx, 5u, frame->payload, payload_len)) {
-            return false;
-        }
-    }
-
-    {
-        uint8_t tail = 0u;
-        if (uart_trans_read(channel, &tail, 1u) != 1u || tail != UART_MUX_TAIL) {
                 return false;
             }
         }
 
+        ring_drop_bytes(ctx, total_len);
         return true;
     }
+}
 
 bool uart_mux_encode_frame(uint8_t src_id,
                            uint8_t dst_mask,

App/uart_trans.h

@@ -55,6 +55,7 @@ void uart_trans_poll(void);
 uint16_t uart_trans_rx_available(uart_channel_t channel);
 uint16_t uart_trans_read(uart_channel_t channel, uint8_t *data, uint16_t max_len);
 uint16_t uart_trans_write(uart_channel_t channel, const uint8_t *data, uint16_t len);
+uint16_t uart_trans_tx_free(uart_channel_t channel);
 void uart_trans_get_stats(uart_channel_t channel, uart_stats_t *stats);
 void uart_trans_reset_stats(uart_channel_t channel);
 void uart_trans_idle_handler(uart_channel_t channel);

Core/Src/iwdg.c

@@ -38,7 +38,7 @@ void MX_IWDG_Init(void)
 
   /* USER CODE END IWDG_Init 1 */
   hiwdg.Instance = IWDG;
-  hiwdg.Init.Prescaler = IWDG_PRESCALER_4;
+  hiwdg.Init.Prescaler = IWDG_PRESCALER_64;
   hiwdg.Init.Reload = 4095;
   if (HAL_IWDG_Init(&hiwdg) != HAL_OK)
   {

Core/Src/main.c

@@ -38,6 +38,7 @@
 #define LED_PIN                     GPIO_PIN_13
 #define LED_PORT                    GPIOC
 #define APP_ROUTE_BUFFER_SIZE       256u
+#define APP_TCP_TO_UART_CHUNK_SIZE  128u
 #define STACK_GUARD_WORD            0xA5A5A5A5u
 #define APP_HEALTH_CHECK_INTERVAL_MS 5000u
 /* USER CODE END PD */
@@ -66,7 +67,11 @@ static void App_RouteMuxUartTraffic(void);
 static void App_RouteTcpTraffic(void);
 static void StackGuard_Init(void);
 static void StackGuard_Check(void);
-static void App_SendToUart(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len);
+static bool App_SendToUart(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len);
+static uint16_t App_SendTcpPayloadToUartRaw(uint8_t uart_index, const uint8_t *data, uint16_t len);
+static bool App_SendTcpPayloadToUartMux(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len);
+static bool App_SendTcpServerPayload(uint8_t instance, const uint8_t *data, uint16_t len);
+static bool App_SendTcpClientPayload(uint8_t instance, const uint8_t *data, uint16_t len);
 /* USER CODE END PFP */
 
 /* Private user code ---------------------------------------------------------*/
@@ -115,6 +120,9 @@ void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
         if (g_led_blink_ticks >= 1000u) {
             g_led_blink_ticks = 0u;
             LED_Toggle();
+            if (hiwdg.Instance == IWDG) {
+                HAL_IWDG_Refresh(&hiwdg);
+            }
         }
     }
 }
@@ -261,48 +269,190 @@ static void App_Init(void)
     }
 }
 
-static void App_SendToUart(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len)
+static bool App_SendTcpServerPayload(uint8_t instance, const uint8_t *data, uint16_t len)
+{
+    return tcp_server_send(instance, data, len) == (int)len;
+}
+
+static bool App_SendTcpClientPayload(uint8_t instance, const uint8_t *data, uint16_t len)
+{
+    return tcp_client_send(instance, data, len) == (int)len;
+}
+
+static bool App_SendToUart(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len)
 {
     const device_config_t *cfg = config_get();
     uart_channel_t channel = (uart_index == LINK_UART_U1) ? UART_CHANNEL_U1 : UART_CHANNEL_U0;
+    uint16_t written;
 
     if (cfg->mux_mode == MUX_MODE_FRAME) {
         uint8_t frame[APP_ROUTE_BUFFER_SIZE + 6u];
         uint16_t frame_len = 0u;
         if (uart_mux_encode_frame(src_id, dst_mask, data, len, frame, &frame_len, sizeof(frame))) {
-            (void)uart_trans_write(channel, frame, frame_len);
+            written = uart_trans_write(channel, frame, frame_len);
+            return written == frame_len;
         }
+        return false;
     } else {
-        (void)uart_trans_write(channel, data, len);
+        written = uart_trans_write(channel, data, len);
+        return written == len;
     }
 }
 
+static uint16_t App_SendTcpPayloadToUartRaw(uint8_t uart_index, const uint8_t *data, uint16_t len)
+{
+    uart_channel_t channel = (uart_index == LINK_UART_U1) ? UART_CHANNEL_U1 : UART_CHANNEL_U0;
+    return uart_trans_write(channel, data, len);
+}
+
+static bool App_SendTcpPayloadToUartMux(uint8_t uart_index, uint8_t src_id, uint8_t dst_mask, const uint8_t *data, uint16_t len)
+{
+    uart_channel_t channel = (uart_index == LINK_UART_U1) ? UART_CHANNEL_U1 : UART_CHANNEL_U0;
+    uint8_t frame[APP_TCP_TO_UART_CHUNK_SIZE + 6u];
+    uint16_t frame_len = 0u;
+
+    if (len == 0u || len > APP_TCP_TO_UART_CHUNK_SIZE) {
+        return false;
+    }
+    if (uart_trans_tx_free(channel) < (uint16_t)(len + 6u)) {
+        return false;
+    }
+    if (!uart_mux_encode_frame(src_id, dst_mask, data, len, frame, &frame_len, sizeof(frame))) {
+        return false;
+    }
+    return uart_trans_write(channel, frame, frame_len) == frame_len;
+}
+
 static void App_RouteTcpTraffic(void)
 {
     const device_config_t *cfg = config_get();
-    uint8_t buffer[APP_ROUTE_BUFFER_SIZE];
+    uint8_t buffer[APP_TCP_TO_UART_CHUNK_SIZE];
 
     for (uint8_t i = 0; i < TCP_SERVER_INSTANCE_COUNT; ++i) {
-        int rc = tcp_server_recv(i, buffer, sizeof(buffer));
+        uint16_t available = tcp_server_rx_available(i);
-        if (rc > 0) {
+        if (available > 0u) {
             uint8_t link_index = (i == 0u) ? CONFIG_LINK_S1 : CONFIG_LINK_S2;
-            App_SendToUart(cfg->links[link_index].uart,
+            uint8_t uart_index = cfg->links[link_index].uart;
-                           config_link_index_to_endpoint(link_index),
+            uint8_t src_id = config_link_index_to_endpoint(link_index);
-                           config_uart_index_to_endpoint(cfg->links[link_index].uart),
+            uint8_t dst_mask = config_uart_index_to_endpoint(uart_index);
-                           buffer,
+            uart_channel_t channel = (uart_index == LINK_UART_U1) ? UART_CHANNEL_U1 : UART_CHANNEL_U0;
-                           (uint16_t)rc);
+
+            if (cfg->mux_mode == MUX_MODE_FRAME) {
+                uint16_t tx_free = uart_trans_tx_free(channel);
+                uint16_t payload_len;
+                if (tx_free <= 6u) {
+                    return;
+                }
+                payload_len = available;
+                if (payload_len > APP_TCP_TO_UART_CHUNK_SIZE) {
+                    payload_len = APP_TCP_TO_UART_CHUNK_SIZE;
+                }
+                if (payload_len > (uint16_t)(tx_free - 6u)) {
+                    payload_len = (uint16_t)(tx_free - 6u);
+                }
+                if (payload_len == 0u) {
+                    return;
+                }
+                payload_len = tcp_server_peek(i, buffer, payload_len);
+                if (payload_len == 0u) {
+                    continue;
+                }
+                if (!App_SendTcpPayloadToUartMux(uart_index, src_id, dst_mask, buffer, payload_len)) {
+                    return;
+                }
+                tcp_server_drop(i, payload_len);
+            } else {
+                uint16_t chunk = available;
+                uint16_t tx_free = uart_trans_tx_free(channel);
+                uint16_t written;
+                if (tx_free == 0u) {
+                    return;
+                }
+                if (chunk > APP_TCP_TO_UART_CHUNK_SIZE) {
+                    chunk = APP_TCP_TO_UART_CHUNK_SIZE;
+                }
+                if (chunk > tx_free) {
+                    chunk = tx_free;
+                }
+                if (chunk == 0u) {
+                    return;
+                }
+                chunk = tcp_server_peek(i, buffer, chunk);
+                if (chunk == 0u) {
+                    continue;
+                }
+                written = App_SendTcpPayloadToUartRaw(uart_index, buffer, chunk);
+                if (written > 0u) {
+                    tcp_server_drop(i, written);
+                }
+                if (written < chunk) {
+                    return;
+                }
+            }
         }
     }
 
     for (uint8_t i = 0; i < TCP_CLIENT_INSTANCE_COUNT; ++i) {
-        int rc = tcp_client_recv(i, buffer, sizeof(buffer));
+        uint16_t available = tcp_client_rx_available(i);
-        if (rc > 0) {
+        if (available > 0u) {
             uint8_t link_index = (i == 0u) ? CONFIG_LINK_C1 : CONFIG_LINK_C2;
-            App_SendToUart(cfg->links[link_index].uart,
+            uint8_t uart_index = cfg->links[link_index].uart;
-                           config_link_index_to_endpoint(link_index),
+            uint8_t src_id = config_link_index_to_endpoint(link_index);
-                           config_uart_index_to_endpoint(cfg->links[link_index].uart),
+            uint8_t dst_mask = config_uart_index_to_endpoint(uart_index);
-                           buffer,
+            uart_channel_t channel = (uart_index == LINK_UART_U1) ? UART_CHANNEL_U1 : UART_CHANNEL_U0;
-                           (uint16_t)rc);
+
+            if (cfg->mux_mode == MUX_MODE_FRAME) {
+                uint16_t tx_free = uart_trans_tx_free(channel);
+                uint16_t payload_len;
+                if (tx_free <= 6u) {
+                    return;
+                }
+                payload_len = available;
+                if (payload_len > APP_TCP_TO_UART_CHUNK_SIZE) {
+                    payload_len = APP_TCP_TO_UART_CHUNK_SIZE;
+                }
+                if (payload_len > (uint16_t)(tx_free - 6u)) {
+                    payload_len = (uint16_t)(tx_free - 6u);
+                }
+                if (payload_len == 0u) {
+                    return;
+                }
+                payload_len = tcp_client_peek(i, buffer, payload_len);
+                if (payload_len == 0u) {
+                    continue;
+                }
+                if (!App_SendTcpPayloadToUartMux(uart_index, src_id, dst_mask, buffer, payload_len)) {
+                    return;
+                }
+                tcp_client_drop(i, payload_len);
+            } else {
+                uint16_t chunk = available;
+                uint16_t tx_free = uart_trans_tx_free(channel);
+                uint16_t written;
+                if (tx_free == 0u) {
+                    return;
+                }
+                if (chunk > APP_TCP_TO_UART_CHUNK_SIZE) {
+                    chunk = APP_TCP_TO_UART_CHUNK_SIZE;
+                }
+                if (chunk > tx_free) {
+                    chunk = tx_free;
+                }
+                if (chunk == 0u) {
+                    return;
+                }
+                chunk = tcp_client_peek(i, buffer, chunk);
+                if (chunk == 0u) {
+                    continue;
+                }
+                written = App_SendTcpPayloadToUartRaw(uart_index, buffer, chunk);
+                if (written > 0u) {
+                    tcp_client_drop(i, written);
+                }
+                if (written < chunk) {
+                    return;
+                }
+            }
         }
     }
 }
@@ -315,37 +465,57 @@ static void App_RouteRawUartTraffic(void)
 
     len = uart_trans_read(UART_CHANNEL_U0, buffer, sizeof(buffer));
     if (len > 0u) {
+        bool routed_ok = true;
         for (uint8_t i = 0; i < CONFIG_LINK_COUNT; ++i) {
+            bool sent = true;
             if (cfg->links[i].enabled == 0u || cfg->links[i].uart != LINK_UART_U0) {
                 continue;
             }
             if (i == CONFIG_LINK_S1) {
-                (void)tcp_server_send(0u, buffer, len);
+                sent = App_SendTcpServerPayload(0u, buffer, len);
             } else if (i == CONFIG_LINK_S2) {
-                (void)tcp_server_send(1u, buffer, len);
+                sent = App_SendTcpServerPayload(1u, buffer, len);
             } else if (i == CONFIG_LINK_C1) {
-                (void)tcp_client_send(0u, buffer, len);
+                sent = App_SendTcpClientPayload(0u, buffer, len);
             } else if (i == CONFIG_LINK_C2) {
-                (void)tcp_client_send(1u, buffer, len);
+                sent = App_SendTcpClientPayload(1u, buffer, len);
             }
+
+            if (!sent) {
+                routed_ok = false;
+            }
+        }
+
+        if (!routed_ok) {
+            return;
         }
     }
 
     len = uart_trans_read(UART_CHANNEL_U1, buffer, sizeof(buffer));
     if (len > 0u) {
+        bool routed_ok = true;
         for (uint8_t i = 0; i < CONFIG_LINK_COUNT; ++i) {
+            bool sent = true;
             if (cfg->links[i].enabled == 0u || cfg->links[i].uart != LINK_UART_U1) {
                 continue;
             }
             if (i == CONFIG_LINK_S1) {
-                (void)tcp_server_send(0u, buffer, len);
+                sent = App_SendTcpServerPayload(0u, buffer, len);
             } else if (i == CONFIG_LINK_S2) {
-                (void)tcp_server_send(1u, buffer, len);
+                sent = App_SendTcpServerPayload(1u, buffer, len);
             } else if (i == CONFIG_LINK_C1) {
-                (void)tcp_client_send(0u, buffer, len);
+                sent = App_SendTcpClientPayload(0u, buffer, len);
             } else if (i == CONFIG_LINK_C2) {
-                (void)tcp_client_send(1u, buffer, len);
+                sent = App_SendTcpClientPayload(1u, buffer, len);
             }
+
+            if (!sent) {
+                routed_ok = false;
+            }
+        }
+
+        if (!routed_ok) {
+            return;
         }
     }
 }
@@ -354,6 +524,7 @@ static void App_RouteMuxUartTraffic(void)
 {
     uart_mux_frame_t frame;
     const device_config_t *cfg = config_get();
+    bool routed_ok;
 
     while (uart_mux_try_extract_frame(UART_CHANNEL_U0, &frame)) {
 #if defined(DEBUG) && (DEBUG != 0)
@@ -366,33 +537,42 @@ static void App_RouteMuxUartTraffic(void)
                 uint16_t response_len = (uint16_t)strlen(response_text);
                 uint16_t frame_len = 0u;
                 if (uart_mux_encode_frame(config_uart_index_to_endpoint(LINK_UART_U0), 0u, (const uint8_t *)response_text, response_len, g_mux_response_frame, &frame_len, sizeof(g_mux_response_frame))) {
-                    (void)uart_trans_write(UART_CHANNEL_U0, g_mux_response_frame, frame_len);
+                    if (uart_trans_write(UART_CHANNEL_U0, g_mux_response_frame, frame_len) != frame_len) {
+                        return;
+                    }
                 }
                 if (result == AT_NEED_REBOOT) {
                     static const char hint[] = "Note: Use AT+SAVE then AT+RESET to apply changes\r\n";
                     response_len = (uint16_t)strlen(hint);
                     if (uart_mux_encode_frame(config_uart_index_to_endpoint(LINK_UART_U0), 0u, (const uint8_t *)hint, response_len, g_mux_response_frame, &frame_len, sizeof(g_mux_response_frame))) {
-                        (void)uart_trans_write(UART_CHANNEL_U0, g_mux_response_frame, frame_len);
+                        if (uart_trans_write(UART_CHANNEL_U0, g_mux_response_frame, frame_len) != frame_len) {
+                            return;
+                        }
                     }
                 }
             }
             continue;
         }
 
+        routed_ok = true;
         if ((frame.dst_mask & ENDPOINT_S1) != 0u) {
-            (void)tcp_server_send(0u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpServerPayload(0u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_S2) != 0u) {
-            (void)tcp_server_send(1u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpServerPayload(1u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_C1) != 0u) {
-            (void)tcp_client_send(0u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpClientPayload(0u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_C2) != 0u) {
-            (void)tcp_client_send(1u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpClientPayload(1u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_UART3) != 0u && cfg->links[CONFIG_LINK_S2].uart == LINK_UART_U1) {
-            App_SendToUart(LINK_UART_U1, frame.src_id, ENDPOINT_UART3, frame.payload, frame.payload_len);
+            routed_ok = App_SendToUart(LINK_UART_U1, frame.src_id, ENDPOINT_UART3, frame.payload, frame.payload_len) && routed_ok;
+        }
+
+        if (!routed_ok) {
+            return;
         }
     }
 
@@ -407,33 +587,42 @@ static void App_RouteMuxUartTraffic(void)
                 uint16_t response_len = (uint16_t)strlen(response_text);
                 uint16_t frame_len = 0u;
                 if (uart_mux_encode_frame(config_uart_index_to_endpoint(LINK_UART_U1), 0u, (const uint8_t *)response_text, response_len, g_mux_response_frame, &frame_len, sizeof(g_mux_response_frame))) {
-                    (void)uart_trans_write(UART_CHANNEL_U1, g_mux_response_frame, frame_len);
+                    if (uart_trans_write(UART_CHANNEL_U1, g_mux_response_frame, frame_len) != frame_len) {
+                        return;
+                    }
                 }
                 if (result == AT_NEED_REBOOT) {
                     static const char hint[] = "Note: Use AT+SAVE then AT+RESET to apply changes\r\n";
                     response_len = (uint16_t)strlen(hint);
                     if (uart_mux_encode_frame(config_uart_index_to_endpoint(LINK_UART_U1), 0u, (const uint8_t *)hint, response_len, g_mux_response_frame, &frame_len, sizeof(g_mux_response_frame))) {
-                        (void)uart_trans_write(UART_CHANNEL_U1, g_mux_response_frame, frame_len);
+                        if (uart_trans_write(UART_CHANNEL_U1, g_mux_response_frame, frame_len) != frame_len) {
+                            return;
+                        }
                     }
                 }
             }
             continue;
         }
 
+        routed_ok = true;
         if ((frame.dst_mask & ENDPOINT_S1) != 0u) {
-            (void)tcp_server_send(0u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpServerPayload(0u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_S2) != 0u) {
-            (void)tcp_server_send(1u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpServerPayload(1u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_C1) != 0u) {
-            (void)tcp_client_send(0u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpClientPayload(0u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_C2) != 0u) {
-            (void)tcp_client_send(1u, frame.payload, frame.payload_len);
+            routed_ok = App_SendTcpClientPayload(1u, frame.payload, frame.payload_len) && routed_ok;
         }
         if ((frame.dst_mask & ENDPOINT_UART2) != 0u) {
-            App_SendToUart(LINK_UART_U0, frame.src_id, ENDPOINT_UART2, frame.payload, frame.payload_len);
+            routed_ok = App_SendToUart(LINK_UART_U0, frame.src_id, ENDPOINT_UART2, frame.payload, frame.payload_len) && routed_ok;
+        }
+
+        if (!routed_ok) {
+            return;
         }
     }
 }
@@ -448,6 +637,7 @@ static void App_Poll(void)
     sys_check_timeouts();
     App_StopLinksIfNeeded();
     App_StartLinksIfNeeded();
+    tcp_server_poll();
     tcp_client_poll();
     uart_trans_poll();
     StackGuard_Check();
@@ -471,9 +661,6 @@ static void App_Poll(void)
         NVIC_SystemReset();
     }
 
-    if (hiwdg.Instance == IWDG) {
-        HAL_IWDG_Refresh(&hiwdg);
-    }
 }
 /* USER CODE END 0 */
 
@@ -488,6 +675,7 @@ int main(void)
   MX_USART3_UART_Init();
   MX_SPI1_Init();
   MX_TIM4_Init();
+  MX_IWDG_Init();
 
   LED_Init();
   LED_StartBlink();

Drivers/CH390/ch390_runtime.c

@@ -40,12 +40,42 @@ static uint8_t g_ch390_ready;
 static ch390_diag_t g_diag;
 static uint8_t g_tx_consecutive_timeout;
 static uint8_t g_chip_reset_count;
+static uint8_t g_link_restart_pending;
 
-#define TX_TIMEOUT_THRESHOLD  3u
+#define TX_BUSY_WAIT_TIMEOUT_MS       10u
-#define CHIP_RESET_MAX        3u
+#define TX_TIMEOUT_RESET_THRESHOLD    6u
+#define HEALTH_FAIL_THRESHOLD         3u
+#define RESTART_PENDING_FLAG          0x01u
+#define HEALTH_FAIL_SHIFT             4u
+#define HEALTH_FAIL_MASK              0xF0u
 
-#define TX_TIMEOUT_THRESHOLD  3u
+static bool ch390_mac_address_valid(const uint8_t *mac);
-#define CHIP_RESET_MAX        3u
+
+static uint8_t ch390_runtime_is_restart_pending(void)
+{
+    return (uint8_t)(g_link_restart_pending & RESTART_PENDING_FLAG);
+}
+
+static void ch390_runtime_set_restart_pending(void)
+{
+    g_link_restart_pending = (uint8_t)(g_link_restart_pending | RESTART_PENDING_FLAG);
+}
+
+static void ch390_runtime_clear_restart_pending(void)
+{
+    g_link_restart_pending = (uint8_t)(g_link_restart_pending & (uint8_t)(~RESTART_PENDING_FLAG));
+}
+
+static uint8_t ch390_runtime_get_health_fail_count(void)
+{
+    return (uint8_t)((g_link_restart_pending & HEALTH_FAIL_MASK) >> HEALTH_FAIL_SHIFT);
+}
+
+static void ch390_runtime_set_health_fail_count(uint8_t count)
+{
+    g_link_restart_pending = (uint8_t)((g_link_restart_pending & (uint8_t)(~HEALTH_FAIL_MASK)) |
+                                       (uint8_t)((count << HEALTH_FAIL_SHIFT) & HEALTH_FAIL_MASK));
+}
 
 static uint8_t ch390_runtime_probe_identity(void)
 {
@@ -76,6 +106,38 @@ static uint8_t ch390_runtime_probe_identity(void)
     return g_diag.id_valid;
 }
 
+static void ch390_runtime_prepare_netif(struct netif *netif)
+{
+    struct ethernetif *ethernetif;
+
+    if (netif == NULL) {
+        return;
+    }
+
+    netif->hwaddr_len = ETHARP_HWADDR_LEN;
+    netif->mtu = 1500;
+    netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_ETHERNET;
+
+    ethernetif = (struct ethernetif *)netif->state;
+    if (ethernetif != NULL) {
+        ethernetif->rx_len = 0u;
+        ethernetif->rx_status = 0u;
+    }
+}
+
+static void ch390_runtime_sync_mac(struct netif *netif)
+{
+    if (netif == NULL) {
+        return;
+    }
+
+    if (ch390_mac_address_valid(netif->hwaddr)) {
+        ch390_set_mac_address(netif->hwaddr);
+    }
+
+    ch390_get_mac(netif->hwaddr);
+}
+
 static void ch390_runtime_refresh_diag(void)
 {
     uint8_t id_valid = ch390_runtime_probe_identity();
@@ -165,7 +227,7 @@ struct pbuf *ch390_runtime_input_frame(struct netif *netif)
     return p;
 }
 
-bool ch390_mac_address_valid(const uint8_t *mac)
+static bool ch390_mac_address_valid(const uint8_t *mac)
 {
     if (mac == NULL) {
         return false;
@@ -180,8 +242,6 @@ bool ch390_mac_address_valid(const uint8_t *mac)
 
 void ch390_runtime_init(struct netif *netif, const uint8_t *mac)
 {
-    struct ethernetif *ethernetif = (struct ethernetif *)netif->state;
-
     SEGGER_RTT_WriteString(0, "ETH init: gpio\r\n");
     ch390_gpio_init();
     SEGGER_RTT_WriteString(0, "ETH init: spi\r\n");
@@ -192,13 +252,7 @@ void ch390_runtime_init(struct netif *netif, const uint8_t *mac)
     SEGGER_RTT_WriteString(0, "ETH init: probe\r\n");
     g_ch390_ready = ch390_runtime_probe_identity();
     if (g_ch390_ready == 0u) {
-        netif->hwaddr_len = ETHARP_HWADDR_LEN;
+        ch390_runtime_prepare_netif(netif);
-        netif->mtu = 1500;
-        netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_ETHERNET;
-
-        ethernetif->rx_len = 0u;
-        ethernetif->rx_status = 0u;
-
         netif_set_link_down(netif);
         SEGGER_RTT_WriteString(0, "ETH init: invalid chip id\r\n");
         return;
@@ -221,14 +275,9 @@ void ch390_runtime_init(struct netif *netif, const uint8_t *mac)
         }
     }
 
-    netif->hwaddr_len = ETHARP_HWADDR_LEN;
     SEGGER_RTT_WriteString(0, "ETH init: getmac\r\n");
+    ch390_runtime_prepare_netif(netif);
     ch390_get_mac(netif->hwaddr);
-    netif->mtu = 1500;
-    netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_ETHERNET;
-
-    ethernetif->rx_len = 0u;
-    ethernetif->rx_status = 0u;
 
     ch390_runtime_refresh_diag();
     g_ch390_ready = g_diag.id_valid;
@@ -306,6 +355,13 @@ void ch390_runtime_check_link(struct netif *netif)
         return;
     }
 
+    if (ch390_runtime_is_restart_pending() != 0u) {
+        netif_set_link_down(netif);
+        ch390_runtime_clear_restart_pending();
+        SEGGER_RTT_WriteString(0, "ETH restart pending: hold link down for app recycle\r\n");
+        return;
+    }
+
     ch390_runtime_refresh_diag();
     link_up = (uint8_t)ch390_get_link_status();
 
@@ -333,8 +389,6 @@ err_t ch390_runtime_output(struct netif *netif, struct pbuf *p)
     struct pbuf *q;
     uint32_t start_tick;
 
-    LWIP_UNUSED_ARG(netif);
-
     if (!g_ch390_ready) {
         LINK_STATS_INC(link.drop);
         return ERR_IF;
@@ -346,15 +400,17 @@ err_t ch390_runtime_output(struct netif *netif, struct pbuf *p)
 
     start_tick = HAL_GetTick();
     while (ch390_read_reg(CH390_TCR) & TCR_TXREQ) {
-        if ((HAL_GetTick() - start_tick) > 10u) {
+        if ((HAL_GetTick() - start_tick) > TX_BUSY_WAIT_TIMEOUT_MS) {
 #if ETH_PAD_SIZE
             pbuf_add_header(p, ETH_PAD_SIZE);
 #endif
             LINK_STATS_INC(link.drop);
             g_diag.tx_packets_timeout++;
+            if (g_tx_consecutive_timeout < 0xFFu) {
                 g_tx_consecutive_timeout++;
-            if (g_tx_consecutive_timeout >= TX_TIMEOUT_THRESHOLD) {
+            }
-                ch390_runtime_emergency_reset();
+            if (g_tx_consecutive_timeout >= TX_TIMEOUT_RESET_THRESHOLD) {
+                (void)ch390_runtime_emergency_reset(netif);
             }
             return ERR_TIMEOUT;
         }
@@ -392,23 +448,26 @@ bool ch390_runtime_is_ready(void)
     return g_ch390_ready != 0u;
 }
 
-bool ch390_runtime_emergency_reset(void)
+bool ch390_runtime_emergency_reset(struct netif *netif)
 {
-    SEGGER_RTT_printf(0, "ETH emergency reset (tx_timeout=%u resets=%u/%u)\r\n",
+    SEGGER_RTT_printf(0, "ETH emergency reset (tx_timeout=%u resets=%u)\r\n",
-                      g_tx_consecutive_timeout, g_chip_reset_count, CHIP_RESET_MAX);
+                      g_tx_consecutive_timeout, g_chip_reset_count);
 
-    if (g_chip_reset_count >= CHIP_RESET_MAX) {
+    if (netif != NULL) {
-        SEGGER_RTT_WriteString(0, "ETH: max resets reached, giving up\r\n");
+        netif_set_link_down(netif);
-        g_ch390_ready = 0u;
-        return false;
     }
 
+    if (g_chip_reset_count < 0xFFu) {
         g_chip_reset_count++;
+    }
     g_tx_consecutive_timeout = 0u;
 
     ch390_software_reset();
     ch390_delay_us(5000u);
     ch390_default_config();
+    ch390_runtime_prepare_netif(netif);
+    ch390_runtime_sync_mac(netif);
+    g_ch390_irq_pending = 0u;
 
     ch390_runtime_refresh_diag();
     g_ch390_ready = g_diag.id_valid;
@@ -418,24 +477,40 @@ bool ch390_runtime_emergency_reset(void)
         return false;
     }
 
+    ch390_runtime_set_health_fail_count(0u);
+    ch390_runtime_set_restart_pending();
     SEGGER_RTT_WriteString(0, "ETH emergency reset: OK\r\n");
     return true;
 }
 
 void ch390_runtime_health_check(struct netif *netif)
 {
+    uint16_t vid;
+    uint8_t fail_count;
+
     if (!g_ch390_ready) {
+        SEGGER_RTT_WriteString(0, "ETH health: chip not ready, attempting reset\r\n");
+        (void)ch390_runtime_emergency_reset(netif);
         return;
     }
 
     /* Verify chip is still responding by reading vendor ID */
-    uint16_t vid = ch390_get_vendor_id();
+    vid = ch390_get_vendor_id();
     if (vid == 0x0000u || vid == 0xFFFFu) {
-        SEGGER_RTT_printf(0, "ETH health: invalid VID=0x%04X, attempting reset\r\n", vid);
+        fail_count = ch390_runtime_get_health_fail_count();
-        netif_set_link_down(netif);
+        if (fail_count < 0x0Fu) {
-        if (ch390_runtime_emergency_reset()) {
+            fail_count++;
-            ch390_runtime_check_link(netif);
         }
+        ch390_runtime_set_health_fail_count(fail_count);
+        if (fail_count >= HEALTH_FAIL_THRESHOLD) {
+            SEGGER_RTT_printf(0, "ETH health: invalid VID=0x%04X streak=%u, attempting reset\r\n",
+                              vid,
+                              fail_count);
+            ch390_runtime_set_health_fail_count(0u);
+            (void)ch390_runtime_emergency_reset(netif);
+        }
+    } else {
+        ch390_runtime_set_health_fail_count(0u);
     }
 }
 

Drivers/CH390/ch390_runtime.h

@@ -58,7 +58,7 @@ void ch390_runtime_check_link(struct netif *netif);
 err_t ch390_runtime_output(struct netif *netif, struct pbuf *p);
 void ch390_runtime_get_diag(ch390_diag_t *diag);
 bool ch390_runtime_is_ready(void);
-bool ch390_runtime_emergency_reset(void);
+bool ch390_runtime_emergency_reset(struct netif *netif);
 void ch390_runtime_health_check(struct netif *netif);
 uint8_t ch390_runtime_get_reset_count(void);
 

MDK-ARM/keil-build-viewer-record.txt

@@ -1,8 +1,8 @@
       Code (inc. data)   RO Data    RW Data    ZI Data      Debug   Object Name
        632          0          0          0          0          0   ch390.o
        616          0         64          0          0          0   ch390_interface.o
-      1858          0         85          5         88          0   ch390_runtime.o
+      2050          0         85          6         88          0   ch390_runtime.o
-      3690          0        591          8       1240          0   config.o
+      3958          0        591          8       1240          0   config.o
          8          0          0          0          0          0   def.o
        124          0          0          0          0          0   dma.o
       1772          0          0          1        240          0   etharp.o
@@ -16,8 +16,8 @@
          0          0          0          0         24          0   ip.o
        778          0          0          2          0          0   ip4.o
         46          0          4          0          0          0   ip4_addr.o
-         0          0          0          0         12          0   iwdg.o
+        44          0          0          0         12          0   iwdg.o
-      2694          0        185         12        272          0   main.o
+      3212          0        185         12        272          0   main.o
        828          0          0         12       4115          0   mem.o
        196          0        244         32       6464          0   memp.o
        582          0          0         12          0          0   netif.o
@@ -33,7 +33,7 @@
        392          0          0          0         32          0   stm32f1xx_hal_flash.o
        240          0          0          0          0          0   stm32f1xx_hal_flash_ex.o
        516          0          0          0          0          0   stm32f1xx_hal_gpio.o
-        12          0          0          0          0          0   stm32f1xx_hal_iwdg.o
+       106          0          0          0          0          0   stm32f1xx_hal_iwdg.o
         60          0          0          0          0          0   stm32f1xx_hal_msp.o
       1240          0         18          0          0          0   stm32f1xx_hal_rcc.o
       1510          0          0          0          0          0   stm32f1xx_hal_spi.o
@@ -43,13 +43,13 @@
        490          0          0          0          0          0   stm32f1xx_it.o
          2          0         24          4          0          0   system_stm32f1xx.o
       3474          0        193         32          0          0   tcp.o
-      1212          0          0          0       1120          0   tcp_client.o
+      1556          0          0          0       1072          0   tcp_client.o
       3684          0          0         36         20          0   tcp_in.o
       3862          0          0          0          0          0   tcp_out.o
-       966          0          0          0       1104          0   tcp_server.o
+      1346          0          0          0       1048          0   tcp_server.o
        164          0          0          0         72          0   tim.o
        374          0         16         12          0          0   timeouts.o
-      1296          0          0          0       2936          0   uart_trans.o
+      1590          0          0          0       2936          0   uart_trans.o
        816          0          0          0        624          0   usart.o
 Object Totals
 
@@ -57,8 +57,8 @@ Memory Map of the image
 
 	Load Region LR_IROM1 
 
-		Execution Region ER_IROM1 (Exec base: 0x08000000, Size: 0x0000D328, Max: 0x00010000, END)
+		Execution Region ER_IROM1 (Exec base: 0x08000000, Size: 0x0000DB7C, Max: 0x00010000, END)
 
-		Execution Region RW_IRAM1 (Exec base: 0x20000000, Size: 0x00005000, Max: 0x00005000, END)
+		Execution Region RW_IRAM1 (Exec base: 0x20000000, Size: 0x00004F98, Max: 0x00005000, END)
 
 Image component sizes

工程调试指南.md

@@ -225,11 +225,21 @@
 5. `AT+MUX?`
 6. `AT+NET=...`
 7. `AT+NET?`
-8. `AT+LINK=...`
+8. `AT+BAUD=...`
-9. `AT+LINK?`
+9. `AT+BAUD?`
-10. `AT+SAVE`
+10. `AT+LINK=...`
-11. `AT+RESET`
+11. `AT+LINK?`
-12. `AT+DEFAULT`
+12. `AT+SAVE`
+13. `AT+RESET`
+14. `AT+DEFAULT`
+
+其中与数据串口相关的固定映射为：
+
+1. `U0 = USART2`
+2. `U1 = USART3`
+3. `AT+BAUD=U0,<baud>` / `AT+BAUD=U1,<baud>` 只更新当前运行配置记录
+4. 新波特率不会立即重初始化 `USART2/USART3`，必须执行 `AT+SAVE` + `AT+RESET` 后按保存值生效
+5. 当前代码接受的波特率范围为 `1200 ~ 921600`
 
 ### 6.2 现场关键规则
 
@@ -238,6 +248,7 @@
 1. 当前现场验证时，配置命令必须保证以换行完成帧。
 2. 若主机侧发送方式不对，现象会很像“配置口完全无响应”。
 3. 因此，配置口不响应时，第一优先级不是改 parser，而是先验证主机端发送格式与接线。
+4. `BAUD` 类命令若查询值已变化，但 `USART2/USART3` 现场波特率尚未变化，不应立即归因为命令无效，应先确认是否已经执行 `AT+SAVE` 与 `AT+RESET`。
 
 ### 6.3 最小验证步骤
 
@@ -247,13 +258,16 @@
 2. 先发 `AT`
 3. 再发 `AT+QUERY`
 4. 再发 `AT+NET?`
-5. 再发 `AT+LINK?`
+5. 再发 `AT+BAUD?`
-6. 修改一个最小参数，例如：
+6. 再发 `AT+LINK?`
+7. 修改一个最小参数，例如：
     - `AT+MUX=1`
-7. 执行：
+    - 或 `AT+BAUD=U1,38400`
+8. 执行：
     - `AT+SAVE`
     - `AT+RESET`
-8. 复位后再次查询，确认配置是否保留
+9. 复位后再次查询，确认配置是否保留
+10. 若本轮验证的是 `AT+BAUD`，还应同步用上位机重新按新波特率连接 `USART2/USART3`，确认数据口实际生效
 
 ### 6.4 持久化失败时怎么查
 
@@ -448,6 +462,106 @@ MUX 模式启动后，一段时间后网口失联。重新插拔网线无法恢
 
 Keil MDK-ARM 构建 0 Error(s), 0 Warning(s)。Flash 52.7 KB / 64.0 KB (82.5%)，RAM 20.0 KB / 20.0 KB (100%)。
 
+### 9.5 2026-04-18 MUX 模式丢包修复记录
+
+#### 现象
+
+在 `MUX=1` 模式下进行持续发送测试时，主机侧发送 `500` 个数据包，只收到 `360` 个，存在明显丢包。
+
+#### 根因
+
+本轮定位确认软件侧至少存在以下两个直接丢包点：
+
+1. `App/uart_trans.c` 中 `uart_mux_try_extract_frame()` 在确认整帧完整前，就先消费 `SYNC` 与 header。若 MUX 帧跨越多个 poll 周期到达，半帧会被提前移出 RX ring，导致当前帧失步并被直接丢弃。
+2. `App/tcp_server.c`、`App/tcp_client.c` 与 `Core/Src/main.c` 的发送路径对背压与短写处理不完整：
+   - `tcp_sndbuf() < len`
+   - `tcp_write()` / `tcp_output()` 返回 `ERR_MEM`
+   - `uart_trans_write()` 只写入部分字节
+
+   以上情况在旧代码中会被上层静默忽略，表现为“发送函数返回但数据实际未完整进入下游链路”。
+
+#### 修复内容
+
+| 文件 | 修改 | 说明 |
+|------|------|------|
+| `App/uart_trans.c` | 将 `uart_mux_try_extract_frame()` 改为先窥视、后消费 | 只有在 `SYNC + header + payload + tail` 全部可用时才推进 `rx_tail`，避免半帧被破坏性消费 |
+| `App/tcp_server.c` | `tcp_server_send()` 对 `tcp_sndbuf()<len` 与 `ERR_MEM` 返回 `0` 并计入错误 | 明确表示本次发送未被底层接收，不再伪装成成功 |
+| `App/tcp_client.c` | `tcp_client_send()` 同步处理背压与 `ERR_MEM` | 逻辑与 server 侧保持一致 |
+| `Core/Src/main.c` | `App_SendToUart()` 检查 `uart_trans_write()` 是否完整写入 | TX ring 空间不足时立即显式失败 |
+| `Core/Src/main.c` | `App_RouteTcpTraffic()` / `App_RouteRawUartTraffic()` / `App_RouteMuxUartTraffic()` 统一检查发送结果 | 不再把背压、短写和未完整提交静默当成成功 |
+
+#### 结果验证
+
+1. Keil MDK-ARM 构建通过，`0 Error(s), 0 Warning(s)`。
+2. 在最新固件下重新进行 MUX 持续发送测试，主机侧发送 `670` 个数据包，接收 `670` 个，`0` 丢包。
+3. 本轮修复未增加新的常驻队列与缓冲区，保持当前 RAM 占用边界不变。
+
+### 9.6 2026-04-24 CH390 emergency reset 恢复语义补齐记录
+
+#### 现象
+
+在 CH390 发生 TX timeout 并触发 `ch390_runtime_emergency_reset()` 后，芯片寄存器访问恢复正常，`VID` 可读、PHY 链路也可能保持 `up`，但 TCP 业务流量仍可能长时间不恢复，表现为“芯片还活着，但网络像失联一样，通常只能重启恢复”。
+
+在后续实现收敛中，又确认仅依赖单次 VID 异常或单次 TX busy 即立刻 reset 过于激进，容易把瞬时抖动误判为芯片失活，因此当前代码已经演化为“带阈值的恢复策略”。
+
+#### 根因
+
+`ch390_runtime_emergency_reset()` 旧实现仅执行 `ch390_software_reset()`、`ch390_default_config()` 与 `diag` 刷新，缺少 cold init 里已有的两层恢复语义：
+
+1. **MAC 对齐未恢复**：旧代码没有重新写回 CH390 `PAR`，也没有把硬件 MAC 重新同步到 `netif->hwaddr`。若软件复位后 CH390 的 MAC 过滤状态与 lwIP 侧缓存身份不一致，现象会表现为寄存器可访问、链路仍在，但单播业务流量不通。
+2. **上层链路回收未触发**：TX-timeout 路径直接调用 `ch390_runtime_emergency_reset()`，没有保证 `App_StopLinksIfNeeded()` / `App_StartLinksIfNeeded()` 观察到一次有效的 link-down 周期，导致旧 TCP client/server 状态可能跨芯片复位残留，业务层没有完成重建。
+3. **恢复策略缺少抖动抑制**：若仅凭单次 TX busy 或单次 VID 异常立即 reset，容易在瞬时总线/链路抖动下过度恢复，放大业务扰动，因此当前实现增加了连续失败阈值和失败计数清零逻辑。
+
+#### 修复内容
+
+| 文件 | 修改 | 说明 |
+|------|------|------|
+| `Drivers/CH390/ch390_runtime.h` | `ch390_runtime_emergency_reset()` 改为接收 `struct netif *` | 让 reset 路径能同时修复 CH390 与 lwIP 可见状态 |
+| `Drivers/CH390/ch390_runtime.c` | 抽取 `ch390_runtime_prepare_netif()` | 在 init / emergency reset 后统一恢复 `hwaddr_len`、`mtu`、`flags` 与 RX 软件状态 |
+| `Drivers/CH390/ch390_runtime.c` | 新增 `ch390_runtime_sync_mac()` | emergency reset 后按当前 `netif->hwaddr` 重写 CH390 `PAR`，并重新同步硬件 MAC 到 lwIP |
+| `Drivers/CH390/ch390_runtime.c` | emergency reset 成功后清 `g_ch390_irq_pending` 并置位 `g_link_restart_pending` | 避免复位前遗留中断状态影响恢复 |
+| `Drivers/CH390/ch390_runtime.c` | `ch390_runtime_check_link()` 增加一次性 hold-down 逻辑 | 保证主循环至少看到一次 link-down，从而触发 app 层 stop/start 回收重建 |
+| `Drivers/CH390/ch390_runtime.c` | TX-timeout 与 health-check 两条 reset 路径统一传入 `netif` | 让两类恢复路径都走同一套 MAC 重同步与链路重建语义 |
+| `Drivers/CH390/ch390_runtime.c` | 为 TX timeout 与 health-check 增加连续失败阈值 | 降低瞬时抖动导致的过度 reset 风险 |
+
+#### 当前实现语义（以源码为准）
+
+1. **TX timeout 阈值**
+   - 单次判定条件：`CH390_TCR.TXREQ` busy-wait 持续超过 `10 ms`
+   - 连续阈值：累计 `6` 次后才触发 `ch390_runtime_emergency_reset()`
+   - 只要有一次成功发送，`g_tx_consecutive_timeout` 立即清零，因此该阈值针对的是**连续失败**，不是累计历史失败次数。
+
+2. **health-check 阈值**
+   - `VID` 单次读到 `0x0000` / `0xFFFF` 并不会立即 reset。
+   - 只有连续 `3` 次异常 VID 才触发 emergency reset。
+   - 若 `g_ch390_ready == 0`，则 health-check 会直接尝试 reset，不再等待 VID 连续计数。
+
+3. **restart-pending 的单次语义**
+   - emergency reset 成功后会置位 restart-pending。
+   - 下一次 `ch390_runtime_check_link()` 先强制执行一次 `netif_set_link_down()`，随后立即清除此标志并提前返回。
+   - 该设计用于保证主循环至少看到一次有效的 logical link-down，从而沿用现有 `App_StopLinksIfNeeded()` / `App_StartLinksIfNeeded()` 路径回收并重建 TCP links。
+
+4. **内部计数与状态**
+   - `g_chip_reset_count`：记录 emergency reset 尝试次数，饱和递增到 `0xFF`。
+   - `g_tx_consecutive_timeout`：记录连续 TX busy 超时次数；成功发送或进入 reset 路径后清零。
+   - health-check 连续失败计数当前与 `g_link_restart_pending` 共用一个状态字节的高位 nibble 存储；当 VID 恢复正常、达到 reset 阈值或 emergency reset 成功时会清零。
+
+5. **失败路径差异**
+   - 只有当 emergency reset 完成后 `g_diag.id_valid` 仍然有效，才会置位 restart-pending 并进入后续 app recycle 语义。
+   - 若 reset 后芯片仍不响应，则仅记录失败并返回，不会伪装成可恢复状态。
+
+#### 预期结果
+
+1. CH390 发生 emergency reset 后，硬件 MAC、`netif->hwaddr` 与当前业务身份重新对齐。
+2. 即使物理网线始终保持连接，主循环仍会在后续 poll 中观察到一次有效 link-down，并按既有 `App_StopLinksIfNeeded()` / `App_StartLinksIfNeeded()` 路径回收并重建 TCP links。
+3. 恢复策略对瞬时异常更保守：只有连续超时或连续 VID 异常达到阈值才会触发 reset，降低误触发恢复的概率。
+4. 复位后的恢复语义与 cold init 更接近，不再停留在“芯片寄存器恢复正常，但业务流量仍死掉”的半恢复状态。
+
+#### 构建验证
+
+1. 已由现场手动执行工程构建，构建通过。
+2. 本轮修改覆盖 `Drivers/CH390/ch390_runtime.c`、`Drivers/CH390/ch390_runtime.h` 与本手册记录，未改动 TCP client/server 模块对外接口。
+
 ---
 
 ## 10. 常见误区

项目技术实现.md

@@ -184,6 +184,68 @@ EN,LPORT,RIP,RPORT,UART
 2. 统一受 `LINK[idx]` 配置驱动
 3. 由调度层决定实例与 UART 的数据交换路径
 
+### 6.4 `v1.1.0` 低 RAM TCP 背压修复
+
+`v1.1.0` 起，`TCP -> UART` 路径补充如下实现约束，用于解决“TCP 接收过快、UART 发送过慢时本地缓存被冲垮”的问题，同时尽量不新增静态 RAM：
+
+1. 继续复用 `tcp_server` / `tcp_client` 现有 `RX ring`，不为每个连接新增独立的大块 pending payload 缓冲。
+2. `tcp_server_on_recv()` / `tcp_client_on_recv()` 不再在回调内立即 `tcp_recved()`。
+3. lwIP 交来的 `pbuf` 在回调中通过 `pbuf_ref()` 转为应用持有，再释放回调上下文的原始引用；后续由应用在主循环中继续把数据泵入 `RX ring`，最终在消费完成后释放。
+4. 当 `RX ring` 暂时装不下时，剩余数据保留在 `hold_pbuf + hold_offset` 中，等待主循环下一轮继续搬运。
+5. 只有当数据真正从 `TCP RX ring` 被 `drop` 掉，也就是已经被下游 `UART` 接收进入发送路径时，才调用 `tcp_recved()` 释放 TCP 接收窗口。
+
+这样做的效果是：
+
+1. `UART` 慢时，TCP 窗口不会继续无条件放大。
+2. 对端发送速度会被 lwIP 接收窗口自然压制。
+3. 修复点建立在已有 ring 与主循环调度之上，不引入 `FreeRTOS` 或新的大块静态缓存。
+
+#### RAW 与 MUX 的分流规则
+
+在 `v1.1.0` 中，`TCP` 侧拿到的都是纯 payload，因此 `TCP` 背压逻辑在 `RAW` 与 `MUX` 两种模式下共用到 `UART commit` 之前：
+
+1. `RAW` 模式：
+   - 主循环先查看 `uart_trans_tx_free()`
+   - 再按 `min(tcp_available, tx_free, APP_TCP_TO_UART_CHUNK_SIZE)` 从 TCP ring `peek`
+   - `uart_trans_write()` 实际写入多少，就 `drop + tcp_recved` 多少
+2. `MUX` 模式：
+   - `TCP` payload 本身不带帧头尾
+   - 只有当 `UART TX free >= payload_len + 6` 时，才在栈上临时编码一帧并一次性写入 `UART TX ring`
+   - 只有整帧成功入队后，才按原始 payload 长度执行 `drop + tcp_recved`
+
+该设计保证：
+
+1. `RAW` 模式允许流式逐步提交
+2. `MUX` 模式保持“单个 UART 输出帧必须完整入队”的语义
+3. `TCP` 接收窗口始终以真实下游消费进度为准，而不是以“回调里已经 memcpy 到本地”作为提交点
+
+#### RAM 与 chunk 策略
+
+为给新增的 `hold_pbuf / hold_offset` 状态字段让位，并进一步降低单轮转发压力，`v1.1.0` 同步采用以下策略：
+
+1. 新增 `APP_TCP_TO_UART_CHUNK_SIZE = 128`
+2. `TCP_SERVER_RX_BUFFER_SIZE` 从 `512` 调整为 `480`
+3. `TCP_CLIENT_RX_BUFFER_SIZE` 从 `512` 调整为 `480`
+
+设计意图：
+
+1. 利用更小的单次转发块提升主循环调度颗粒度
+2. 让 `MUX` 模式下 `payload + 6` 更容易完整进入 `UART TX ring`
+3. 在静态 RAM 已接近上限时，为少量新状态字段回收空间
+
+#### 构建基线
+
+`v1.1.0` 以 `MDK-ARM/TCP2UART.uvprojx` 的 `TCP2UART` Target 为构建验收基线。
+
+当前一次通过的参考结果：
+
+1. `errors = 0`
+2. `warnings = 0`
+3. `flash_bytes = 56544`
+4. `ram_bytes = 20376`
+
+该结果说明修复后工程仍满足 `STM32F103R8T6` 的 `20KB RAM` 上限，但余量已经很小；后续若继续增加功能，应优先考虑复用现有缓冲与状态，而不是增加新的静态大数组。
+
 ## 七、主循环实现方向
 
 主循环仍保持裸机轮询风格：