在stc开发板上实现PID算法控制温度。ds1820读取温度，12864显示，单片机产生PWM波通过mos开关来控制电阻加热时间。(In the stc development board to achieve PID control temperature. Ds1820 read temperature, 12864 display, single-chip PWM wave generated by the mos switch to control the resistance heat