自制的单片机简单实验板原理图和PCB制板图,由PROTEL99设计；可以实现端口实验，定时器实验，计数器实验，中断实验，发声实验,串口通讯实验，I2C总线实验,SPI总线实验-Self-made single-chip simple experimental board schematic and PCB system board diagram, from PROTEL99 design can realize port experiments, timer experiment, coun