diff --git a/include/public.h b/include/public.h
index 395bbd3..6035300 100644
--- a/include/public.h
+++ b/include/public.h
@@ -13,6 +13,7 @@ __sfr __at (0xE7) ISP_CONTR;
 extern char __xdata reset_password[RESET_PASSWORD_LENGTH];
 extern char __xdata receice_password[RESET_PASSWORD_LENGTH];
 
+#define BEEP P2_5
 
 void delay_10us(u16 ten_us);
 void delay_ms(u16 ms);
diff --git a/src/main.c b/src/main.c
index 690465c..380fa93 100644
--- a/src/main.c
+++ b/src/main.c
@@ -33,11 +33,14 @@ void main(void)
 		// led_all_off();
 		// delay_ms(1000);
 	// 实验二：流水灯
-		LED = ~i;
-		i = rotate_left(i,1);
-		delay_ms(1000);
+		// LED = ~i;
+		// i = rotate_left(i,1);
+		// delay_ms(1000);
+	// 实验三：蜂鸣器
+		BEEP=!BEEP;
+		delay_10us(100);
 
-		printf("Hello,world!\r\n");
+		// printf("Hello,world!\r\n");
 	}		
 }