the probs occur in keypad due to keydebouncing. If you want to do it properly, use 74922 or 74923 key encoders with keypad to avoid it. Refer this book also
MY EXPERIENCE IN PARALLEL PORT INTERFACING
connect data out(4 bit in case of 922) to the data pins of the uC and DAta available to the separate pin. When DA=1 then key is pressed and no problems occur to u. But the cost of 922 is high. Don't go for other keyencoders like 74148 bcz they don't have keydebounce mask. The proper capacitance should be applied to 922 to mask keydebounce and tht is explained in tht book.
Bibin John
www.bibinjohn.tk
MY EXPERIENCE IN PARALLEL PORT INTERFACING
connect data out(4 bit in case of 922) to the data pins of the uC and DAta available to the separate pin. When DA=1 then key is pressed and no problems occur to u. But the cost of 922 is high. Don't go for other keyencoders like 74148 bcz they don't have keydebounce mask. The proper capacitance should be applied to 922 to mask keydebounce and tht is explained in tht book.
Bibin John
www.bibinjohn.tk