Keypads operation, Computer Engineering

The 16 keys (4x4 matrixes) keypads diagram is shown in figure 4 above. Let see how the keypad is connected. Each square of the alphanumeric has to be pushed to make a switch or connection, which connects the horizontal wires (Rows) with the vertical wires (Columns). For example, if button ‘A' is pressed, it will connect COL1 with ROW4, or pressing button '5' will connect COL2 with ROW2.

The keypads are usually organized in a matrix of rows and columns. The microcontroller will access both the rows and columns through the ports. If a key pressed, a row and column make a contact; otherwise there will be no connection between rows and columns.

Since the switches or keys are all interconnected, I need differentiate between the each one of them. I have connected four 10K Ohms resistors each on the interface board to pull lines (COL1- COL 4) high (set as input) and connected them PORTA (RA1-RA4) on the microcontroller. These four lines are been read in the program. So if no key is pressed, these lines will all read high. The other four pins (ROW-ROW4) are connected to pins on PORTB (RB0-RB3) the PIC18F452 and set as output. The full schematic diagram for this section could be found in the appendix.

To interface the keypad, two main processes listed below must occur:

I. Key press detection
II. Key identification
Moreover, there are two ways of performing key press detection:

1) The interrupt method (Port B - Change interrupt can be used)
2) Scanning method

Posted Date: 2/23/2013 12:40:37 AM | Location : United States







Related Discussions:- Keypads operation, Assignment Help, Ask Question on Keypads operation, Get Answer, Expert's Help, Keypads operation Discussions

Write discussion on Keypads operation
Your posts are moderated
Related Questions
graphical adapters and input methods in computer graphics

Line A Line is, on a simple level, a mark connecting 2 points. However, how lines are used in an image is extremely important. By varying the quality of line used in an image,

Q. Illustration to demonstrate design of sequential circuits? Let us take an illustration to demonstrate above process. Suppose we want to design 2-bit binary counter employing

What is blocking probability? Blocking Probability: The blocking probability P is described as the probability like all the servers in system are busy. If all the servers ar

Suppose you''re given n numbers and asked to find a number that is greater than or equal to the median a) What is the lower bound for the worst case complexity of this problem?

Syntax of $display and $strobe -  $display ("format_string", par_1, par_2, ... ); -  $strobe ("format_string", par_1, par_2, ... ); -  $monitor ("format_string", par_1, p

Explain any three parsing techniques. Following are three parsing techniques: Top-down parsing: This parsing can be viewed as an attempt to get left-most derivations of an

Java uses layout managers to lay out components in a consistent manner across all windowing platforms. As Java's layout managers aren't tied to absolute sizing and positioning, the

shell script to find whether the given number is Armstrong or not

What are the requirements a dialog program must fulfill? A dialog program must fulfil the following requirements A user friendly user interface. - Format and consistency