本代码完成用PC机并口实现SPI功能，能够有效的实用并口完成数据传输-The complete code with the PC parallel port to implement the SPI function, parallel to the effective completion of data transfer utility

实显示采集到的心电波形信号，有SD卡存储和USB数据传输功能-Real display collected ECG signal, SD card storage and USB data transfer function