fix sn format

basic/sn.c

@@ -1,9 +1,9 @@
 #include "sn.h"
 
 #include <stdbool.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <stdio.h>
 
 /*******************************************************************************
  *                                   EXTERN                                    *
@@ -15,15 +15,15 @@ sn_t* xs_device_info_get() {  //
   sn_t* info = (sn_t*)DEVICE_INFO_START_ADD;
   m_sn       = *info;
 
-  if (m_sn.year < 0) {
+  if (m_sn.year == 255) {
     m_sn.year = 0;
   }
 
-  if (m_sn.weak < 0) {
+  if (m_sn.weak == 255) {
     m_sn.weak = 0;
   }
 
-  if (m_sn.index < 0) {
+  if (m_sn.index == 65535) {
     m_sn.index = 0;
   }
 
@@ -34,7 +34,6 @@ const char* sn_get_str() {
   sn_t*       info = xs_device_info_get();
   static char sn_str[32];
 
-
   sprintf(sn_str, "%s%02d%02d%04d", "SN", info->year, info->weak, info->index);
   return sn_str;
 }