fix type

mini-beieli-node.ino

@@ -893,8 +893,8 @@ static void receiveMessage(void *pContext, uint8_t port, const uint8_t *pMessage
     byte buf[9];
     struct {
       byte dummy;
-      int32_t gram_A;
-      int32_t gram_B;
+      uint32_t gram_A;
+      uint32_t gram_B;
     } value;
   } bytearray;