说明：  DAC8574驱动代码，DAC8574 4输出IIC接口 STM32F10X
(The DAC8574 is a low-power, quad channel, 16-bit buffered voltage output DAC. Its on-chip precision output amplifier allows rail-to-rail output swing to be achieved. The DAC8574 utilizes an I2C compatible two wire serial interface supporting high-speed interface mode with address support of up to sixteen DAC8574s for a total of 64 channels on the bus.)