diff --git a/prj/TCPClient/Debug/debug.c b/prj/TCPClient/Debug/debug.c
index 529a789..885e3a6 100644
--- a/prj/TCPClient/Debug/debug.c
+++ b/prj/TCPClient/Debug/debug.c
@@ -95,6 +95,15 @@ void USART_Printf_Init(uint32_t baudrate)
     GPIO_InitTypeDef  GPIO_InitStructure;
     USART_InitTypeDef USART_InitStructure;
 
+/* When sensor occupies USART3, skip debug UART init entirely */
+#include "mini212g2.h"
+#if SENSOR_USE_USART3 && (DEBUG == DEBUG_UART3)
+    (void)GPIO_InitStructure;
+    (void)USART_InitStructure;
+    (void)baudrate;
+    return;   /* USART3 reserved for sensor, printf disabled */
+#endif
+
 #if(DEBUG == DEBUG_UART1)
     RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);
 
@@ -221,8 +230,11 @@ __attribute__((used)) int _write(int fd, char *buf, int size)
         while(USART_GetFlagStatus(USART2, USART_FLAG_TC) == RESET);
         USART_SendData(USART2, *buf++);
 #elif(DEBUG == DEBUG_UART3)
+  #include "mini212g2.h"
+  #if !SENSOR_USE_USART3
         while(USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET);
         USART_SendData(USART3, *buf++);
+  #endif
 #endif
     }
 #endif
diff --git a/prj/TCPClient/Debug/mini212g2.c b/prj/TCPClient/Debug/mini212g2.c
index c16000b..b0432bb 100644
--- a/prj/TCPClient/Debug/mini212g2.c
+++ b/prj/TCPClient/Debug/mini212g2.c
@@ -57,19 +57,34 @@ static void Sensor_UART_Init(void)
     GPIO_InitTypeDef  gpio = {0};
     USART_InitTypeDef usart = {0};
 
+#if SENSOR_USE_USART3
+    /* USART3: PB10=TX  PB11=RX
+     * NOTE: This reuses the debug printf port. printf is disabled. */
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
+    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
+
+    gpio.GPIO_Pin   = GPIO_Pin_10;
+    gpio.GPIO_Speed = GPIO_Speed_50MHz;
+    gpio.GPIO_Mode  = GPIO_Mode_AF_PP;
+    GPIO_Init(GPIOB, &gpio);
+
+    gpio.GPIO_Pin  = GPIO_Pin_11;
+    gpio.GPIO_Mode = GPIO_Mode_IN_FLOATING;
+    GPIO_Init(GPIOB, &gpio);
+#else
+    /* USART2: PA2=TX  PA3=RX */
     RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
 
-    /* TX: PA2 AF push-pull */
     gpio.GPIO_Pin   = GPIO_Pin_2;
     gpio.GPIO_Speed = GPIO_Speed_50MHz;
     gpio.GPIO_Mode  = GPIO_Mode_AF_PP;
     GPIO_Init(GPIOA, &gpio);
 
-    /* RX: PA3 floating input */
     gpio.GPIO_Pin  = GPIO_Pin_3;
     gpio.GPIO_Mode = GPIO_Mode_IN_FLOATING;
     GPIO_Init(GPIOA, &gpio);
+#endif
 
     usart.USART_BaudRate            = SENSOR_UART_BAUD;
     usart.USART_WordLength          = USART_WordLength_8b;
@@ -122,6 +137,14 @@ static void Sensor_FlushRx(void)
  * Public API
  * ============================================================ */
 
+/* ============================================================
+ * Debug inspection variables (watch in JTAG debugger)
+ * ============================================================ */
+volatile uint8_t  sensor_init_ok       = 0;
+volatile uint8_t  sensor_init_fail     = 0;
+volatile uint8_t  sensor_last_resp[8]  = {0};
+volatile uint8_t  sensor_last_resp_len = 0;
+
 int Mini212G2_SendCmd(const uint8_t *cmd, uint8_t len)
 {
     uint8_t resp[8];
@@ -129,10 +152,14 @@ int Mini212G2_SendCmd(const uint8_t *cmd, uint8_t len)
     Sensor_SendBytes(cmd, len);
 
     int n = Sensor_ReadResp(resp, sizeof(resp), 200);
+    /* Save last response for debugger inspection */
+    sensor_last_resp_len = (uint8_t)n;
+    for (int j = 0; j < n && j < 8; j++)
+        sensor_last_resp[j] = resp[j];
+
     if (n == ACK_LEN && memcmp(resp, ACK_PATTERN, ACK_LEN) == 0)
         return 0;
 
-    /* Debug: print what we got */
     printf("[Sensor] resp(%d):", n);
     for (int j = 0; j < n; j++) printf(" %02x", resp[j]);
     printf("\r\n");
@@ -151,7 +178,8 @@ int Mini212G2_Init(void)
     int ok = 0, fail = 0;
 
     Sensor_UART_Init();
-    printf("[Sensor] UART2 init (PA2=TX PA3=RX, 115200)\r\n");
+    printf("[Sensor] UART init %d, baud=%d\r\n",
+           (int)(SENSOR_UART == USART3 ? 3 : 2), (int)SENSOR_UART_BAUD);
 
     /* Sensor needs several seconds to boot after power-on */
     printf("[Sensor] Waiting 3s for sensor boot...\r\n");
@@ -202,6 +230,8 @@ int Mini212G2_Init(void)
     Delay_Ms(500);
 
     printf("[Sensor] Config result: %d ok, %d fail\r\n", ok, fail);
+    sensor_init_ok   = (uint8_t)ok;
+    sensor_init_fail = (uint8_t)fail;
 
     /* Print current digital video status for verification */
     Mini212G2_PrintDigitalVideoStatus();
diff --git a/prj/TCPClient/Debug/mini212g2.h b/prj/TCPClient/Debug/mini212g2.h
index 6fb9431..3f3e01f 100644
--- a/prj/TCPClient/Debug/mini212g2.h
+++ b/prj/TCPClient/Debug/mini212g2.h
@@ -3,13 +3,22 @@
 
 #include "ch32v30x.h"
 
+/* ---- Temporary debug wiring option ----
+ * Set to 1 to use USART3 (PB10=TX PB11=RX) for sensor communication.
+ * This steals the debug printf port — use JTAG debugger for observation.
+ * Set to 0 for normal operation (USART2 / PA2+PA3). */
+#define SENSOR_USE_USART3    1
+
 /* Set to 1 to enable UART commands to configure sensor at boot.
  * Set to 0 if sensor is pre-configured via USB to auto-output CMOS/DVP.
- * NOTE: PA2/PA3 may conflict with Ethernet — keep 0 unless UART is wired. */
-#define SENSOR_UART_ENABLE   0
-
-/* Sensor UART: USART2  PA2=TX  PA3=RX */
-#define SENSOR_UART          USART2
+ * Automatically forced to 1 when SENSOR_USE_USART3 is enabled. */
+#if SENSOR_USE_USART3
+  #define SENSOR_UART_ENABLE   1
+  #define SENSOR_UART          USART3
+#else
+  #define SENSOR_UART_ENABLE   0
+  #define SENSOR_UART          USART2
+#endif
 #define SENSOR_UART_BAUD     115200
 
 /**
@@ -19,6 +28,16 @@
  */
 int Mini212G2_Init(void);
 
+/* Debug variables — inspect via JTAG debugger when printf is unavailable.
+ * sensor_init_ok:   number of commands that succeeded
+ * sensor_init_fail: number of commands that failed
+ * sensor_last_resp[]: raw bytes of last failed response
+ * sensor_last_resp_len: length of last response */
+extern volatile uint8_t  sensor_init_ok;
+extern volatile uint8_t  sensor_init_fail;
+extern volatile uint8_t  sensor_last_resp[8];
+extern volatile uint8_t  sensor_last_resp_len;
+
 #if SENSOR_UART_ENABLE
 /**
  * Send a raw protocol command and wait for ACK.