diff --git a/main.c b/main.c
--- a/main.c
+++ b/main.c
@@ -20,6 +20,13 @@
 #define SW_LEFT GPIOB, GPIO_Pin_5
 #define SW_RIGHT GPIOB, GPIO_Pin_4
 
+/* Extern variables ----------------------------------------------------------*/
+extern __IO uint8_t Receive_Buffer[64];
+extern __IO  uint32_t Receive_length ;
+extern __IO  uint32_t length ;
+uint8_t Send_Buffer[64];
+uint32_t packet_sent=1;
+uint32_t packet_receive=1;
 
 static __IO uint32_t TimingDelay;