A matrix keyboard scanning program that feels better

I came up with this program when I was writing a calculator program. I always felt that the commonly used keyboard scanning program was troublesome to use. It always had to scan line by line, and it looked very cumbersome. So I came up with a matrix keyboard scanning program. The principle is very simple!

The basic idea of ​​this program is that two intersecting straight lines have only one intersection point. To put it simply, it detects the rows first and then the columns, or vice versa.

This keyboard scanning subroutine is a parameterless function with a return value, so you just need to calculate an array beforehand!

The following is the implementation of the sub-function. I only use a 3*4 matrix keyboard as an example here. The principle is the same! [page] 
============================================================================== 
uchar code key_table[]= 
{ 
0x77, 
0x7b, 
0x7d 
, 0xb7 , 
0xbb 
, 0xbd 
, 
0xd7, 0xdb, 
0xdd, 
0xe7, 
0xeb, 
0xed 
}; 
/*The above array must be calculated in advance. You can get the value corresponding to the corresponding key by connecting the row and column values ​​together*/

unsigned char key_scan(void ) 
{ 
unsigned char i, key_code; /*Variable declaration*/ 
key_port = 0x0f; /*Here key_port is a GPIO port defined in the previous macro.

First set the row (or column) */                  
if (key_port ! = 0x0f) /* If a key is pressed, the initial value of GPIO will change,

The following statements will be executed*/ 
{ 
delay(5); /*The delay here is to achieve debounce, which will not be introduced here*/ 
if(key_port != 0x0f) /*Confirm that a key is really pressed*/ 
{ 
key_code = key_port; /*Assign the value of the row (or column) to key_code*/ 
key_port = 0xf0; /*Then set the column (or row)*/ 
key_code |= key_port; /*Combine the row and column values ​​and assign them to key_code*/ 
for(i = 0; i < 12; i++) /*Because there is only one key_code corresponding to each key pressed,

Therefore, according to the number of keys on the matrix keyboard, the corresponding FOR loop can be used to determine which key is pressed*/ 
{ 
if(key_table[i] == key_code) 
{ 
key = i+1; 
break; 
} 
} 
} 
} 
else key = 0; 
return key; /*The returned KEY value is the key at the corresponding position*/ 
}