Keypad, which is quite a familiar term nowadays, is nothing but a block of buttons with symbols, alphabets and numerals labeled. Or else, it can be regarded as an assembly of digits and symbols allowing the user to enter the numeric values, symbols or alphabets. They are normally used for user-friendly applications including calculators, push-button phones and digital door locks. The keypad labels include alphabets, numeric digits or symbols in accordance with the purpose of the device. For example, a computer system uses an alphanumeric keypad whereas a telephone system uses numeric ones with a limited number of symbols. Also, one can make a keypad which can enter images and illustrations as per the requirement.
Keypads are mainly used where a data entry operation is required since they are regarded as the most efficient and reliable input devices. One can find applications of keyboards in gadgets and complex systems starting from the cell phones to the systems used in the space mission.
OpenLab keypad is a 4×4 matrix type and has 8 pins to connect with ATmega32 microcontroller, so it will use an 8-bit port for interfacing. The keypad can be used in both pull up and pull down modes. J18 is the keypad port connector and it should be connected to any one of the port connectors. J34 helps to select pull up and pull down modes.
It is easy to use and interface the keypad inside the OpenLab by simply plugging in the cable and burning the program. OpenLab uses a 4*4 matrix keypad with numbers, alphabets, and symbols which can be connected to PORT B by default with pull up or pull down mode selected by the user.
OpenLab keypad comes with 8 pins to connect with ATmega32 microcontroller, so it will need an 8-bit port for interfacing. The keypad can be used in both pull up and pull down modes. J34 jumper helps to select the mode. J18 is the keypad port connector and it should be connected to any one of the port connectors.
*Col – column pins, Row – row pins
From the above image, J18 is the connector which provides keypad output and J38 is the input to the micro-controller inside the OpenLab. J39 is the default connector for keypad interfacing. Connect J39 to J18 using an FRC cable as depicted in the image below.
Pull-up and pull-down modes are used to minimize the noise in the circuit. The keypad used in the OpenLab works on both pull up and pull down modes. Pull up mode provides more noise immunity than pull-down mode.
Pull up and pull down modes can be selected by re-inserting the jumper later all the key-inputs are captured by the controller after burning the program by the end user.