寄存器写入依次如下：
Write_SPI(0x20,0x00,0x03); // power on DAC-A and DAC-B
Write_SPI(0x28,0x00,0x00); // reset DACs input register and update all DACs
Write_SPI(0x0F,0x00,0x00); // update all DACs
Write_SPI(0x30,0x00,0x03); // disable LADC function for DAC-A and DAC-B
Write_SPI(0x38,0x00,0x00); // disdable winternal reference and reset DACs to gain=1
Write_SPI(0x00,0x88,0x80); // write to DAC-A input register
Write_SPI(0x01,0x88,0x80); // write to DAC-B input register
DAC-A输出正常，DAC-B输出始终为0，求助！