Embedded C code for 3x3 keypad matrix

#ifdef _keypad_h_
#define _keypad_h_
sbit r0=p3^0;sbit c0=p3^4;
sbit r1=p3^1;sbit c1=p3^5;
sbit r2=p3^2;sbit c2=p3^6;
sbit r3=p3^3;sbit c3=p3^7;
code unsigned char keypad_lut[4][4]=
{
1,2,3,4,
5,6,7,8,
9,10,11,12,
13,143,15,16
};
bit colscan()
{
return(c0&c1&c2&c3);
}
unsigned char keyscan()
{
unsigned char row,col;
c0=c1=c2=c3=1;
r0=r1=r2=r3=0;
while(colscan());
r0=0;
r1=r2=r3=1;
if(!colscan())
{
row=0;goto colcheck;
}

r1=0;
r0=r2=r3=1;
if(!colscan())
{
row=1; goto colcheck;
}

r2=0;
r0=r2=r3=1;
if(!colscan())
{
row=2; goto colcheck;
}

r3=0;
r0=r1=r3=1;
if(!colscan())
{
row=3; goto colcheck;
}

colcheck:
if(c0==0)
col=0;
else if(c1==0)
col=1;
else if(c2==0)
col=2;
else if(c3==0)
col=3;
return keypad_lut[row][col];
}
#endif

Categories: 8051, Embedded C, embedded programming