Simple 4*4 matrix keyboard scanning program-EEWORLD

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/*
Program effect: Press any key, LED displays the data read back by P0, and the 4*4 matrix keyboard is connected to P0 port
*/
#include //header file
unsigned char key=0xff; //Define a variable to store the key value
void readkey(); //Read key sub-function, get key value
void main() //Main function
{
while(1)
{
readkey(); //Read key value
if(key!=0xff) //Judge whether any key is pressed
P2=~key; //Here is the inversion: because the LED is common cathode, it displays the pressed value
}
}
void readkey() //Read keyboard sub-function
{
P0=0xfe; //Pull the first column low and scan whether any key is pressed. The key values of the first column are: 0, 4, 8, C
key=P0; //Read keyboard value
if(key!=0xfe) //If key! =0xfe, indicating that a key is pressed, then return
return; //Otherwise continue to scan the next column
P0=0xfd;
key=P0;
if(key!=0xfd)
return;
P0=0xfb;
key=P0;
if(key!=0xfb)
return;
P0=0xf7;
key=P0;
if(key!=0xf7)
return;
key=0xff;
}

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