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51单片机考勤系统下位机程序，可以配合上位机软件实现考勤功能，将hex文件下载到51单片机即可使用(51 MCU control procedures can be achieved with the PC software attendance function, the hex file into the microcontroller 51 can be used)

串口与pc机通讯，51单片机例程，只需要修改io口即可实现。(Serial communication with pc, 51 MCU routine, you only need to modify the io port can be realized.)

一种简单的心率测量系统设计，能显示并进行上下限报警(A simple heart rate measurement system design, and upper and lower alarm)

步进电机是将电脉冲信号转变为角位移或线位移的开环控制电机，是现代数字程序控制系统中的主要执行元件，应用极为广泛。。在非超载的情况下，电机的转速、停止的位置只取决于脉冲信号的频率和脉冲数，而不受负载变化的影响，当步进驱动器接收到一个脉冲信号，它就驱动步进电机按设定的方向转动一个固定的角度，称为“步距角”，它的旋转是以固定的角度一步一步运行的。可以通过控制脉冲个数来控制角位移量，从而达到准确定位的目的；同时可以通过控制脉冲频率来控制电机转动的速度和加速度，从而达到调速的目的。(Stepper motor is an open loop control motor which transforms electrical pulse signal into angular displacement or linear displacement. It is the main executive element in modern digital control system, and is widely applied. In the case of non overloaded, the motor speed and stop position depends only on the pulse frequency and pulse number, regardless of load changes, when the stepper driver receives a pulse signal, it drives stepper motor to set the direction of rotation of a fixed angle, called "step", it is the rotation of the fixed point of the operation step by step. We can control the angular displacement by controlling the number of pulses, so as to achieve the goal of accurate positioning. At the same time, we can control the speed and acceleration of motor rotation by controlling the pulse frequency, so as to achieve the purpose of speed regulation.)

说明：  i2c红外 小车扫描 简单程序 扫描准确(smart car scan easy program)

pic单片机Proteus仿真NEC格式红外，编码，解码，调制三部分(PIC proteus ad da )

本程序利用51单片机的定时器中断产生时间信号，同时具有通过按键调节时间的功能，还可设置闹钟(This procedure using 51 single-chip timer interrupt time signal, but also has the functions via buttons adjust the time, but also set the alarm)

CD4051/CC4051是单8通道数字控制模拟电子开关，有三个二进控制输入端A、B、C和INH输入，具有低导通阻抗和很低的截止漏电流。(CD4051/CC4051 is single channel 8 digital controlled analog electronic switch, there are three binary control input A, B, C and INH input, has low conduction resistance and very low by leakage current.)

HM20通用型压力变送器 资料很全 值得下载 (HM20 Universal Pressure Transmitter)

stm32f4 的usb鼠标主机程序，简单的修改即可成为自己的工程(stm32f4 usb mouse host)