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
1. (a) Given a baseband bus with station 1 located at 10m, station 2 located at 1000m, and station 3 located at 1010 meters (see diagram above). If the data rate of the bus is 10 M

Some of the plug-ins have proven unstable. These have been moved into a split download, which should be available anywhere you got the GIMP, in the file gimp-plugins-unstable-VERSI

Why should project managers complete hard problems first in an OOSAD project?   Ans) The query really holds good in general for each situation in life. It is one of the prin

1)      Short both I/Ps of NAND gate & use the gate as an inverter. 2)      Connect any one of the two I/Ps to VCC & use the remaining I/P & use the gate as an inverter.

Swing is a GUI toolkit for Java. It is one kind of the Java Foundation Classes (JFC). Swing haves graphical user interface (GUI) widgets such as text boxes, buttons, split-panes, a

Define secondary memory. This memory holds those pages that are not present in main memory. The secondary memory is usually a high speed disk. It is known as the swap evice, an

What is Electronic Data Interchange? Electronic Data Interchange (EDI): It is used by organizations for transactions which arise on regular basis to a pre-found format.

Define Assembly Assembly is a one deployable unit that contains information about the execution of classes, structures and interfaces. it also keeps the information about itsel

Q. Benefits of Device controllers? Using device controllers for attaching I/O devices to a computer system in place of connecting them directly to system bus has subsequent ben

Write a script that will read from a file x and y data points in the following format: x   0    y  1 x  1.3  y  2.2 x  2.2  y  6 x  3.4  y  7.4 The format of each line in the