I compiled more than 200 different PHP versions (every version released since 4.3.0) plus HHVM for you to use.In this project, we will go over how to integrate a keyboard with an arduino board so that the arduino can read the keys being pressed by a user.For example, the matrix keypad we are using has 16 keys (0-9, A-D, *, #), yet only 8 output pins.With a linear keypad, there would have to be 17 output pins (one for each key and a ground pin) in order to work.When you download, change the name to folder to something other than Keypad.If the folder and the file you are importing have the same name, it won't work.
We connect the first pin of the keypad to D9, the second pin to D8, the third pin to D7, the fourth pin to D6, the fifth pin to D5, the sixth pin to D4, the seventh pin to D3, and the eighth pin to D2.
Later, in another project, we will connect the keypad circuit, so that it will get displayed on an LCD.
But for now, for simplicity purposes, we start at simply showing the key pressed on the computer.
The matrix encoding scheme allows for less output pins and thus much less connections that have to made for the keypad to work.
In this way, they are more efficient than linear keypads, being that they have less wiring.