ʾʹõԴ
USER BUTTON  ---   PB2
LDE          ---   PB1


ʾḶ́
1ϵʱӡΪEXTIģʽ¼ѣ
2ȴ3s
3stopģʽWFE; ʱ¼STOP
4ѺָϵͳʱãͬʱLEDGPIO