Nuttx下新建路径以及motors

前言

之前在nuttx下编写应用的时候，陷入了之前写单片机代码的误区，没有很好的讲逻辑层和驱动层的代码分割开来，
导致写出来的程序，可读性和可移植性太差，这次参考ardupilot的思路重新整理下实现的过程；

目标

实现一个电机接口库，具体目标如下：
1.这个库应该是建立在nuttx上；
2.利用os原有的PWM驱动以及IO驱动实现电机的控制接口；
3.抽象出电机模型（例如差速模型、姿态模型、自行车模型、单电机模型...）；
4.文件目录层级：
	|—../app/libraries
					|—motor
							|—差速模型（*.c、.h、.....）
							|—自行车模型（*.c、.h、.....）
							|—.......
							|—单电机模型（*.c、.h、.....）
					|—InertialSensor
					....
					|—编译文件（makefile、Kconfig、make.dep、make.defs）

文件的大概目录就是这样，下面结合实际的例子来详细说明。

libraries

 libraries这个文件夹是新建的，就从这里开始吧～

然后编译器在编译的时候才找得到新建的源文件，从而编译；
首先在app下面按照上面的文件目录层级建立好所需要的源文件，接下怎么呢？
刚开始我蒙圈了，经验告诉我去看看readme,里面有如下描述：（我就只挑重点的来了）

Building NuttX with Board-Specific Pieces Outside the Source Tree
-----------------------------------------------------------------
   3) If you like the random collection of stuff in the apps/ directory
      but just want to expand the existing components with your own,
      external sub-directory then there is an easy way to that too:
      You just create a sympolic link in the apps/ directory that
      redirects to your application sub-directory.

      In order to be incorporated into the build, the directory that
      you link under the apps/ directory should contain (1) a Makefile
      that supports the clean and distclean targets (see other Makefiles
      for examples), and (2) a tiny Make.defs file that simply adds the
      custon build directories to the variable CONFIGURED_APPS like:

        CONFIGURED_APPS += my_directory1 my_directory2

      The apps/Makefile will always automatically check for the
      existence of subdirectories containing a Makefile and a Make.defs
      file.  The Makefile will be used only to support cleaning operations.
      The Make.defs file provides the set of directories to be built; these
      directories must