设计一个单片机与DA0832组成的波形发生器。要求产生周期，幅值均是固定。但波形是可选的，分别为正弦波、方波、三角波、锯齿波。并通过虚拟示波器观察波形的周期是否正确。-Design consists of a microcontroller and DA0832 waveform generator. Cycles required to produce the amplitude are fixed. But the waveform is optional, namely sine, squ