Keyboard - detecting keys
Because we don't have enough inputs on the arduion we can implement a key matrix to detect which keys are pressed. This way the needed input are the number of columns plus rows. The way it works is that we send a signal on one row and check which columns receive it. Then check the next row the same way. The basic idea of the matrix scanning: There is the problem called ghosting - keys which are not really pressed register as being pressed. Using diodes we can prevent the effect. Here is how it happens when diodes are not present: As you can see the right column does receive a signal when it is the top row's turn to send it, because the signal goes through the top-left pressed key to the left column and then to the bottom column through the bottom-left key and then to the bottom row through the bottom-right key. That means that the top right switch is registered as pressed, but it's not. And here is the same scenario, but with diodes: It is a good idea to te...
