本代码是PID在S函数中的实现，但不同之处在于，本代码先把PID变成状态空间表达式，更加易懂，为本人独创。-This code is the PID in the S function, but the difference is that, this code to put the PID into the state space expressions, more understandable, for my original.

TI公司MSP430F149常用函数调用，包括串口通信，1602初始化，PID函数，MPU6050使用等函数。-TI' s MSP430F149 common function calls, including serial communication, 1602 initialization, PID function, MPU6050 use and other functions.