======= ESP IDF Files =======

  * <project-directory-name>/CMakeLists.txt
    * set project name: project(<project-name>)
  * <project-directory-name>/sdkconfig
    * SDK configuration variables (do not edit) 
  * <project-directory-name>/sdkconfig.default
    * optional
    * SDK configuration variables - user serviceable parts inside
    * changing values: 
      * enter into sdkconfig.default
      * remove from sdkconfig
      * run: idf.py fullclean build
    * CONFIG_FREERTOS_HZ= (maximum value: 1000, default: 100)
  *  <project-directory-name>/build/
    * directory used by the build process
  * <project-directory-name>/main/ 
    * source code dirctory