diff --git a/test/hardware/blikvm_test_v4.c b/test/hardware/blikvm_test_v4.c
index 4a50e66..c69b178 100755
--- a/test/hardware/blikvm_test_v4.c
+++ b/test/hardware/blikvm_test_v4.c
@@ -1,11 +1,17 @@
 /*******************************************************************************
  *                            CHANGE HISTORY                                   *
  *-----------------------------------------------------------------------------*
+ * test error code use binary system, the error code result use OR(|) *
+ * 0b00000011(dec:3) : uart or usb error *
+ * 0b00000100(dec:4) : rtc error *
+ * 0b00001000(dec:8) : wifi error*
+ * 0b00010000(dec:16) : atx error*
  *   <Date>   | <Version> | <Author>      |            <Description>           *
  *-----------------------------------------------------------------------------*
  * 2023-05-28 | 0.1       | Thomasvon     |                 create
  ******************************************************************************/
 
+
 #include <pthread.h>
 #include <stdio.h>
 #include <unistd.h>