secondary principle schematics或secondary principle diagrams参考资料：有使用说明书和必要的电路图和原理图。The instrument must be accompanied by instructions manual with the necessary schematics and drawings.如果可能，掌握各个设备串口的原理图是很有用的。If possible it is often useful to have a schematic of the serial port of each device in a system.给出硬件接...
