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How the Matrix Keypad works with a Micro controller?

The matrix is controlled by a micro-controller.

Matrix Keypad when there is no Button press

For the above 16-button 4×4 matrix, 8 pins of the micro controller will be used.

The first 4 pins will be OUTPUTS and will be connected to the COLUMN wires, while the other 4 pins will be INPUTS and will be connected to the ROW wires.

The OUTPUTS of the micro-controller will NOT all have power at the same time.

The outputs will go high one by one in cycle.

During this time, it will also monitor the inputs for a signal. As long as all inputs are LOW , the Micro-controller will take no action.

Now, suppose that the operator presses the button 3C.

Button 3C of the Matrix Keypad is pressed

This button has connect the matrix col C, with the matrix row 3.

When the output C of the micro-controller becomes HIGH, the signal arrives also at the input 3 of the micro-controller, through the pressed button.

The micro-controller check the 4 inputs and detects that when the specific output (C) is high, there is a HIGH signal at the input 3.

So, this means that the input C3 is pressed!

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