Wednesday, July 25, 2012

How the Matrix Keypad works with a Micro controller?

Fig: Matrix Keypad when there is no Button press

The matrix is controlled by a micro-controller.
]For the above 16-button 4x4 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.

Please see the below image.

Fig: 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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