initial

说明：  2015年电赛国测题，频率测量。基于stm32的频率测量。优点：精密度高，代码简单(In 2015, the National Test of Electricity Competition, Frequency Measurement. Frequency measurement based on stm32. Advantages: High precision, simple code)

4*4键盘的测试，按下一个键指示灯显示一个对应的键码(4* 4 keyboard test, press a key indicator shows a corresponding key code)

一个简单的pid模型。运行后可以获得pid控制曲线。通过修改p/i/d的参数，观看控制曲线的变化。(A simple pid model running under matlab. It could simulate and output the PID curve with manual setting p/i/d values.)

AVR单片机 定时器的应用 初始化 以及中断程序(AVR microcontroller timer application initialization and interrupt routine)

MSP430 角度传感器MPU6050程序_ccs(MSP430 angle sensor MPU6050 program _ccs)

变压器（Transformer）是利用电磁感应的原理来改变交流电压的装置，主要构件是初级线圈、次级线圈和铁芯（磁芯）。主要功能有：电压变换、电流变换、阻抗变换、隔离、稳压（磁饱和变压器）等。按用途可以分为：电力变压器和特殊变压器（电炉变、整流变、工频试验变压器、调压器、矿用变、音频变压器、中频变压器、高频变压器、冲击变压器、仪用变压器、电子变压器、电抗器、互感器等）。电路符号常用T当作编号的开头.例: T01, T201等。(A transformer (Transformer) is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the iron core (core). The main functions are: voltage transformation, current transformation, impedance transformation, isolation, voltage stabilizing (magnetic saturation transformer) and so on. It can be divided into power transformers and special transformers (electric transformer, rectifier and transformer, power frequency transformer, voltage regulator, mine change, audio transformer, intermediate frequency transformer, high-frequency transformer, shock transformer, transformer, transformer, reactor, intersenser, etc.). Circuit symbols usually use T as the beginning of numbering. Examples: T01, T201 and so on.)

AT89C51驱动直流电机，有仿真跟C语言。直流电机驱动，实现直流电机的正、反转，PWM调速。(AT89C51-driven DC motor, a simulation with the C language. DC motor drives, DC motor forward and reverse PWM speed control.)

User subroutine to describe friction in contact simulations

说明：  关于stm32系列所有芯片的内部IC的读取操作，属于高级历程；(About the high-level application of STM32 chip part of the code process, STM32 code.)

DALI调光详细讲解，软硬件齐全，不可多得的好材料(DALI dimming elaborate hardware and software is complete, the rare good material)