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Code Library Keypad Interfacing with microcontroller AT89S51 is an electronic device falling under the category of a microcomputer. Being a highly powerful microcomputer, AT89S51 provides effective solutions to numerous embedded control applications.
Such keypads are seen in telephones and other commonly seen applications. Here in this chapter, we discuss in detail about the process of keypad interfacing with an AT89S51 microcontroller. Matrix Keypad Interfacing The advantage of a matrix keypad is that the use of it will allow the programmer to reduce the number of pins to be used.
It may look like one needs 16 pins for the microcontroller to be connected to the matrix keypad but practically 16 inputs of keypad interface are possible with the 8 pins of a microcontroller port.
All 8 lines can be connected to the same port or different ports based on the application requirements. Embedded C course is free with this course for a short period of time Learn more about the course Matrix keypad interfacing and key press identification can be explained in a step by step manner which involves a software. First, we give a HIGH on row pins. When a key is pressed, the corresponding row and column get shorted.
In the second step, a software scans the pins connected to the columns. If it detects a HIGH on any particular column, then it is found that the key press has been made of a key in that column. The third step is to figure out which key is pressed exactly. For this, the software writes logic high on row pins sequentially. The pin of the column on which the pressed key is situated will become high. Procedure of Working Connect four column pins and four-row pins to the microcontroller port.
Either row or column should be configured as input and other as output.
8051 Microcontroller Assembly Language Programming
Example 2 What is a Programming Language? Programming in the sense of Microcontrollers or any computer means writing a sequence of instructions that are executed by the processor in a particular order to perform a predefined task. Programming also involves debugging and troubleshooting of instructions and instruction sequence to make sure that the desired task is performed. Like any language, Programming Languages have certain words, grammar and rules. There are three types or levels of Programming Languages for Microcontroller. These levels are based on how closely the statements in the language resemble the operations or tasks performed by the Microcontroller. This is the lowest level of programming languages and is the language that a Microcontroller or Microprocessor actually understands.
AT89C51 - 8 bit Microcontroller
Embedded Systems - 8051 Microcontroller