简单的libusb 供学习，在android上 有mk的写法-Simple libusb for learning on the android has written mk

详细解释了xv6系统 Makefile文件和runoff文件每一行代码的意思，以及这两个文件的功能-A detailed explanation of the xv6 system Makefile and runoff file the meaning of each line of code, and the function of these two files

uart测试代码，可测试发送和接收，附编译好的可执行文件，android下编译的Android.mk文件-uart test code, you can test sending and receiving, with the compiled executable file, android compiled under Android.mk file