Add API to get serial number as bytes

Author: sandeepmistry

src/ECCX08.cpp

@@ -61,20 +61,29 @@ void ECCX08Class::end()
 #endif
 }
 
-String ECCX08Class::serialNumber()
+int ECCX08Class::serialNumber(byte sn[])
 {
-  String result = (char*)NULL;
-  byte sn[12];
-
   if (!read(0, 0, &sn[0], 4)) {
-    return result;
+    return 0;
   }
 
   if (!read(0, 2, &sn[4], 4)) {
-    return result;
+    return 0;
   }
 
   if (!read(0, 3, &sn[8], 4)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+String ECCX08Class::serialNumber()
+{
+  String result = (char*)NULL;
+  byte sn[12];
+
+  if (!serialNumber(sn)) {
     return result;
   }
 

src/ECCX08.h

@@ -32,6 +32,7 @@ class ECCX08Class
   int begin();
   void end();
 
+  int serialNumber(byte sn[]);
   String serialNumber();
 
   long random(long max);