diff --git a/my_pro/myproject.c b/my_pro/myproject.c
index 69c8255..020f310 100644
--- a/my_pro/myproject.c
+++ b/my_pro/myproject.c
@@ -422,14 +422,14 @@ static void serial_thread_entry(void *parameter)
     char buf[] = "hello rt-thread!\r\n";
     serial = rt_device_find("uart3");
 
-    if (dev)
+    if (serial)
         rt_device_open(serial, RT_DEVICE_FLAG_RDWR);
     else
         return;
 
     while (1)
     {
-        rt_device_write(dev, 0, buf, rt_strlen(buf));
+        rt_device_write(serial, 0, buf, rt_strlen(buf));
         rt_thread_mdelay(500);
     }
     // char ch[105];