基于51单片机的简易电子琴，能利用所给键盘的1，2，3，4，5，6，7，8八个键，能够发出7个不同的音调，而且有一个按键可以自动播放歌曲，要求按键按下时发声，松开延时一小段时间，中间再按别的键则发另外一音调的声音，当系统扫描到键盘按下，则快速检测出是哪一个按键被按下，然后单片机的定时器启动，发出一定频率的脉冲，该频率的脉冲经喇叭驱动电路放大滤波后，就会发出相应的音调。如果在前一个按下的键发声的同时有另一个按键被按下，则启动中断系统。前面的发音停止，转到后按的键的发音程序。发出后按的键的音调。-5

Overview- A passenger want to check the current status of bus like what is the current location and what time will it take to reach to his/her stop etc. So, we are planning to make intelligent bus transportation system which is briefly described b

电动工具无刷电机控制解决方案，基于单片机控制的无刷电机驱动，可立即启停，高性能，低耗能，锂电池充电。-Electric tools brushless motor control solutions, brushless motor driver based on single chip microcomputer control, can immediately stop, high performance, low energy, lithium battery.