简易电子琴，利用所给键盘的1，2，3，4，5，6，7，8八个键，能够发出8个不同的音调，并且要求按下按键发声，松开延时一段时间停止，中间再按别的键则发另一音调的声音。当系统扫描到键盘上有键被按下，则快速检测出是哪一个键被按下，然后单片机的定时器被启动，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键被按下，则启用中断系统，前面键的发音停止，转到后按的键的发音程序，发出后按的键的音。-Simple keyboard, use the keyboard to 1,2,3,4,5,6,7,8 eight keys, issued eight different tone, and asked to press the button sound, release delay for some time to stop the middle and then the other key is made of another tone of voice. When the system scans the keyboard key is pressed to quickly detect which key is pressed, then the MCU timer is activated, emits a certain frequency of pulse, the frequency of the pulse amplifying and filtering by the speaker drive circuit, will send the appropriate tone. If the previous key pressed sound at the same time another key is pressed, the interrupt system is enabled, stopped in front of key pronunciation, pronunciation program go to press the key issue after key press sound.