Introduction - If you have any usage issues, please Google them yourself
Keil C used to prepare an embedded single-chip key drive, all using C language description, for my original. This procedure used to achieve at least the case of single-chip pin to achieve the largest number of keys, such as the use of N root line to achieve N* (N-1) keys, use keys table, and the realization of a long press, short press , multiplexing and other functions keys.