diff --git a/components/net/freemodbus/Kconfig b/components/net/freemodbus/Kconfig
index 9321c61a0eae5322a82253f4a36c70ea7b62e49a..1dbeca31d9b3f34e888c21eced19d19efced88cd 100644
--- a/components/net/freemodbus/Kconfig
+++ b/components/net/freemodbus/Kconfig
@@ -12,6 +12,16 @@ config RT_USING_MODBUS
 		config RT_MODBUS_SLAVE_RTU
 			bool "RTU slave mode"
 			default n
+            if RT_MODBUS_SLAVE_RTU
+                config RT_MODBUS_SLAVE_USE_CONTROL_PIN
+                    bool "Use Contorl Pin"
+                    default n
+                    if RT_MODBUS_SLAVE_USE_CONTROL_PIN
+                        config MODBUS_SLAVE_RT_CONTROL_PIN_INDEX
+                            int "pin index for RS485 TX/RX select"
+                            default 10
+                    endif
+            endif
 	endif
 
 endmenu
diff --git a/components/net/freemodbus/port/portserial.c b/components/net/freemodbus/port/portserial.c
index 0ad33d7a7c5741dcfb1f4a244d96538e97a7c462..7c546a1691e50e780e4f6c1505dd83475829533e 100644
--- a/components/net/freemodbus/port/portserial.c
+++ b/components/net/freemodbus/port/portserial.c
@@ -56,8 +56,9 @@ BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
      * set 485 mode receive and transmit control IO
      * @note MODBUS_SLAVE_RT_CONTROL_PIN_INDEX need be defined by user
      */
-    //rt_pin_mode(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
-
+#if defined(RT_MODBUS_SLAVE_USE_CONTROL_PIN)
+    rt_pin_mode(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
+#endif
     /* set serial name */
     if (ucPORT == 1) {
 #if defined(RT_USING_UART1) || defined(RT_USING_REMAP_UART1)
@@ -127,12 +128,16 @@ void vMBPortSerialEnable(BOOL xRxEnable, BOOL xTxEnable)
         /* enable RX interrupt */
         serial->ops->control(serial, RT_DEVICE_CTRL_SET_INT, (void *)RT_DEVICE_FLAG_INT_RX);
         /* switch 485 to receive mode */
-        //rt_pin_write(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_LOW);
+#if defined(RT_MODBUS_SLAVE_USE_CONTROL_PIN)
+        rt_pin_write(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_LOW);
+#endif
     }
     else
     {
         /* switch 485 to transmit mode */
-        //rt_pin_write(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_HIGH);
+#if defined(RT_MODBUS_SLAVE_USE_CONTROL_PIN)
+        rt_pin_write(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_HIGH);
+#endif
         /* disable RX interrupt */
         serial->ops->control(serial, RT_DEVICE_CTRL_CLR_INT, (void *)RT_DEVICE_FLAG_INT_RX);
     }
diff --git a/components/net/freemodbus/port/user_mb_app.h b/components/net/freemodbus/port/user_mb_app.h
index ce3e69f38263ed522587cb0a5a34ec15dda780c6..71f490f5fac69a4beaddc8409e3cce87e4f0773a 100644
--- a/components/net/freemodbus/port/user_mb_app.h
+++ b/components/net/freemodbus/port/user_mb_app.h
@@ -25,9 +25,6 @@
 /* salve mode: discrete's all address */
 #define          S_DI_RESERVE                     0
 /* slave mode: holding register"s startup address */
-#define         S_SYSTEM_START_ADDR               0x003A
-#define         S_SYSTEM_SLAVE_ID_ADDR            0x0040
-#define         S_SYSTEM_KEEP_TEMP                0x0009
 
 /* -----------------------Master Defines -------------------------------------*/
 #define M_DISCRETE_INPUT_START        1