 
 // コマンドの文字列の先頭の文字と処理する関数を保持する構造体
 struct TASK_FUNC {
-  String prefix;
+  char* prefix;
   TASK_FUNC_PTR func;
 };
 

     example => do/write/3?val=1
     example => do/write/3?val=HIGH
   */
  {String("do/write/"), &doWriteTask},

  /*
     Swith digital pin mode.

     {val}   => write value.
     example => ao/write/1?val=100
   */
  {"ao/write/", &aoWriteTask},

  /*
     Read DI port.
