了解并掌握AD-DA转换芯片的基本原理 2.了解掌握I2C总线接口的工作原理及一般编程方法。通过改D[4]的值，实现模拟输出，学员观察学习板上DA处LED的亮度变化-Understand and master the AD-DA converter chips basic principles 2. Understand the working principle of the I2C bus interface and general programming. Through the chan