thanks but actually i've try this b4 n i can detect two keys pressed in the same row only. when i come to detect the keys pressed at different rows,let say both keys located at column 1,row 1 and row2.
at the time the first key is pressed, the voltage i detect at the input pin of column 1 is about 1.2v( Vcc is 3V, so stil can b considered as logic low) but once the key at row2 pressed, the voltage detected at col1 become 2.4( which considered as logic high).
tht's y it suddenly detect by the chips as no key been pressed in col1. i really dono wat is happening.
can anyone help me? thanks