51相关外围扩展电路，包括IIC器件PCF8563,PCF8576,ZLG7290；液晶控制电路LCD1602和12864；步进电机控制电路；伺服电机控制电路 AD，DC控制；温度，湿度控制等等，有很好的参考价值。-51 related to the expansion of the external circuit, including the IIC device PCF8563, PCF8576, ZLG7290　and LCD1602 LCD control circuit 12864　stepper motor control circuit　servo motor control circuit　AD, DC control　temperature, humidity control and so on, there is a good reference价值.