My latest project has 64 buttons.
Computer keyboard matrix circuit.
The trick is to use a keyboard matrix e g.
The key matrix is a grid of circuits underneath the keys.
Go back to the first matrix circuit but take into account the green overlay this time to see how this solution looks.
A keyboard matrix is a great way to add buttons without using up all of your i o pins.
A large part of this circuitry makes up the key matrix.
It has its own processor and circuitry that carries information to and from that processor.
In all keyboards except for capacitive models.
This way the pin set to 1 will never source current and this nearly makes it an od pin.
More on that to follow.
The keyboard is a typical scanning matrix of keys so i suspected a problem with one of the column wires.
Look carefully for any discoloration that would possibly indicate the problem area.
This same code and circuit are what i m using for a new project.
5 rows x 15 columns and quickly cycle through each row column allowing you to use 2n pins only for a n x n matrix.
When you press any particular key it completes this circuit thus enabling the processor to determine the location of the key that was pressed.
These are the actual matrix of the keyboard.
If you press the h key on a keyboard matrix circuit for instance the scanner will notice the switch being activated at the intersection of the wires where the h key is located.
The key matrix is a collection of circuits under the keyboard which is broken at a specific point under every key which results in making the circuit incomplete.
Thus allowing it to determine which key is pressed.
A keyboard matrix circuit is a design used in most electronic musical keyboards and computer keyboards in which the key switches are connected by a grid of wires similar to a diode matrix for example 16 wires arranged in 8 rows and 8 columns can connect 64 keys sufficient for a full five octaves of range 61 notes.
It also controls the illumination of the caps lock num lock and scroll lock lights.
By scanning these crossings a keyboard controller can determine which.
There is a tiny flexible cap at every key position.
You can read more about how that.
I verified the wiring with a multimeter but the problem was that one column driver output pin on the microcontroller gave out just 0 volts.
The keyboard switch matrix is wired to its inputs and it processes the incoming keystrokes and sends the results down a serial cable the keyboard cord to a receiver in the main computer box.
In this keyboard matrix tutorial i showed how a 9 button matrix works.
A keyboard is a lot like a miniature computer.
Of course this isn t real od but it solves the current loop problem in a keyboard matrix.
When we lift off the matrix take great care.
