The most classic SCM matrix scanner C Language

/*************************************** **************************************** ***********
Keyboard 3*4 Scanner
Entry parameters:
Exit parameters:
Key code: EE de be, 7E, Ed, DD, BD, 7d, EB, DB, BB, 7b
0 1 2 3 4 5 6 7 8 9 A B
**************************************** **************************************** *************/
Void delay (uchar D );
Uchar keyv ()
{Uchar readkey,;
P2 = 0xf8; // determine the row and column position
If (P2 = 0xf8)
Return (keynum); // if no key is set, 0 is returned.
If (P2 = 0xf8) // judge again. The purpose is to ensure that the detection is correct.
Return (keynum );
Else
{Delay (0); // call the latency function to shake the front key.
For (A = 0; A <3; A ++) // The following is the classic calculated key value (determine the location of the closed key)
{P2 = _ cror _ (0xfb, );
If (p24 = 0) break;
If (P25 = 0) break;
If (P26 = 0) break;
If (P2 = 0) break;
}
Readkey = P2; // obtain the key value
For (; P2! = 0xf8; P2 = 0xf8); // wait until the key is released to shake along the key
Flag = 1;
Return (readkey); // return the primary function with a key value
}
}
/*************************************** **************************************** **********
Calculate and return the number key-value module so that the buttons can be directly determined when the subsequent program calls the module.
Other branches can be executed.
**************************************** **************************************** ***********/
Uchar keycode (void)
{Uchar key_code;
While (1)
{
Key_code = keyv ();
Switch (key_code)
{
Case 0xEE: keynum = 0; break;
Case 0xde: keynum = 1; break;
Case 0xbe: keynum = 2; break;
Case 0x7e: keynum = 3; break;
Case 0xed: keynum = 4; break;
Case 0xdd: keynum = 5; break;
Case 0xbd: keynum = 6; break;
Case 0x7d: keynum = 7; break;
Case 0xeb: keynum = 8; break;
Case 0xdb: keynum = 9; break;
Case 0xbb: keynum = 0x0a; break;
Case 0x7b: keynum = 0x0b; break;
Default: break;
}
Return (keynum );
}
}

 

 

# Include

Unsigned char code table [] = {0xc0, 0xf9, 0xa4, 0xb0, 0x99, // 0 ~ 4
0x92,0x82, 0xf8, 0x80, 0x90, // 5 ~ 9
0x88,0x83, 0xa7, 0xa1, 0x86, 0x8e}; // ~ F

Void keyscan ();
Void delay10ms (unsigned char time );
Void dispaly (unsigned char K );

Unsigned char key, temp;

Void main () // main program
{
While (1)
{
Keyscan ();
}
}

Void keyscan () // a key scan subroutine
{
P1 = 0xff;
P1_3 = 0;
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Delay10ms (1 );
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Temp = p1;
Temp & = 0xf0;

Switch (temp)
{
Case 0x70:
Key = 1; break;
Case 0xb0:
Key = 2; break;
Case 0xd0:
Key = 3; break;
}
Dispaly (key );
}
}

P1 = 0xff;
P1_2 = 0;
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Delay10ms (1 );
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Temp = p1;
Temp & = 0xf0;

Switch (temp)
{
Case 0x70:
Key = 4; break;
Case 0xb0:
Key = 5; break;
Case 0xd0:
Key = 6; break;
}
Dispaly (key );
}
}

P1 = 0xff;
P1_1 = 0;
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Delay10ms (1 );
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Temp = p1;
Temp & = 0xf0;

Switch (temp)
{
Case 0x70:
Key = 7; break;
Case 0xb0:
Key = 8; break;
Case 0xd0:
Key = 9; break;
}
Dispaly (key );
}
}

P1 = 0xff;
P1_0 = 0;
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Delay10ms (1 );
Temp = p1;
Temp & = 0xf0;
If (temp! = 0xf0)
{
Temp = p1;
Temp & = 0xf0;

Switch (temp)
{
Case 0x70:
Key = 14; break;
Case 0xb0:
Key = 0; break;
Case 0xd0:
Key = 15; break;
}
Dispaly (key );
}
}
}

// Latency Program
Void delay10ms (unsigned char time)
{
Unsigned char A, B, C;
For (A = 0; A for (B = 0; B <10; B ++)
For (C = 0; C <120; C ++)
;
}

Void dispaly (unsigned char K) // display program
{
P0 = table [k];
P2_1 = 0;
}