实现AD9914的基本控制，复杂控制可建立在此基本程序上。(it can control the ad9914 dds)

AD9914是一款直接数字频率合成器(DDS)，内置一个12位数模转换器，目标工作速率最高达3.5 GSPS。(The AD9914 is a direct digital synthesizer (DDS) featuring a 12-bit DAC. The AD9914 uses advanced DDS technology, coupled with an internal high speed, high performance DAC to form a digitally