介绍了正弦脉宽调制的一半方法，原理，及实现过程，是编程者一个不错的参考资料-Describes the half sine pulse width modulation methods, principles, and implementation process is a good programmers reference

在dac 上显示一个波图，刚刚输出的时候是sine 的图 开动按钮后发出不同的图像-Write a C program that creates a waveform generator. It should start by outputting a sine wave to DAC0. Each time SW1 is pressed then released, the wave form should change, first to a triangle wave, then