Question

Given the following code and keypad layout, what will the function GetKey() return when it is run while keys 2, 3, 7, B, E, and F are pressed?




DDRH = 0x0F;
RDRH = 0x00;
PERH = 0x00;
PIEH = 0x00;
PTH = 0x0F;


unsigned char GetKey(void)
{ unsigned char KeyMask[16] =
{ 0xEE, 0xDE, 0xBE, 0x7E,
0XED, 0xDD, 0xBD, 0x7D,
0xEB, 0xDB, 0xBB, 0x7B,
0xE7, 0xD7, 0xB7, 0x77
};
int i;
char Key;

for (Key=0, i=0; i<16; i++)
{ PTH = KeyMask[i];
if (PTH == KeyMask[i])
{ if (i<10) Key = ‘0’ + i;
else Key = ‘A’+ i - 10;
}
}
PTH = 0x0F;
return (Key);
}

0 Assert PORT keypad row o o PORTkeypad row11 PORT2 keypad row2 2 4 Assert Assert Assert keypad row 3 3 PORTx 3] Vcc 4 10 K Read kevpad column 0 PORTx 4] Vcc 10 K Read keypad column 1 PORTx[5) Vcc 10 K Read keypad col umn 2 PORTx[6] Vcc 10 K Read keypad column 3 PORTx[7]

Answer 1

I just saw a code ...and it used common.h header and used the function getKey() ..to get the keys pressed ....
For up he used a macro like UPKEY , DOWNKEY etc...
The code isnt compiling on my system i guess common.h is not ansi ...I want to implement the same thing ..In my maze game these are the keys used for the direction
W--up,s -- down,a ---left,d--right.
I want to use the cursor keys for that ....any ANSI fucntion that can help me with it ....The function GetKey() return when it is run while keys 2, 3, 7, B, E, and F are pressed ,it returns the value of getKey() function from the above circuit diagram when 2 is pressed it returns o+2,when 3 is pressed it returns 0+3, when 7 is pressed it returns o+7,when B is pressed it returns A+55,when E is pressed it returns A+59, when F is pressed it returns A+70. As in the above code in for loop the given condition of if statements says that value of i should be i<10 so we implement the above conditions on given values of 2,3,7 for alphabates we concerders their ASSCCi then the conditon is in else statement so it follows A+i-10 in this answer can be finded out. Thank you Hope the above imformation is enough to understand the concept and finding the getKey() function returns value.