In this article, I will guide you step by step programming part as well as structure of keypad. Before starting this article, you should know how to write your first program in keil and how to used input output ports of microcontroller. Because keypad is used as a input with microcontroller. Matrix Keypads are mostly used in calculators, mobile phones, telephones, ATM etc.
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In this article, I will guide you step by step programming part as well as structure of keypad. Before starting this article, you should know how to write your first program in keil and how to used input output ports of microcontroller.
Because keypad is used as a input with microcontroller. Matrix Keypads are mostly used in calculators, mobile phones, telephones, ATM etc. It is used when a number of input switches are required. In this article we will study how to interface keypad with microcontroller. An experiment will show the keypad interfacing. User will give input through keypad and then that input will be displayed on LCD. But the arrangement is changed by connecting switches in a special way. Now we need only 8 pins of microcontroller to connect keypad to it.
The column pins Col 1—Col4 are connected to the microcontroller as the inputs pinsand the rows pins Row 1—Row 4 are connected to the output pins of the microcontroller. Normally, all the column pins are pulled high by internal or external pull up resistors. Now we can read the status of each switch through scanning. Columns pins are used as input pins, and rows pins are used as output. If a low logic is given to all the Rows and high logic is given to each Column.
Output of the corresponding column goes to go low. Since we have made all the rows zero so this gives the column number of the pressed key.
Each row is one by one set to zero by the microcontroller and the earlier detected column is checked and obviously it becomes zero. The row due to which the column gets zero is the row number of the pressed key.
LCD is connected to Port 2 of the microcontroller for displaying output. LED is connected to port 1 pin 3. P1, P2 are used as output ports. P3 lower bits are used as outputs while upper bits as inputs. Then LCD is initialized by specific commands. All columns are given high logic and all rows are given low logic. Check each column for it. Give low logic to single row and high logic to other rows, repeat this process for other rows and row is found.
For Example: In pressing of 1, Col 1 goes low. For Col 1 check the row1. In above screenshot, I pressed 2. It is then written on LCD. When button is pressed, Led will get on and then then off after some delay. The number will appear on the screen as long as other number is not pressed. This display arrangement can be changed by arranging the code in different way.
LCD Interfacing with 8051 Microcontroller
Code Explanation I interffacing tried to explain the code through comments in code itself. You may need to use RS as explained in the Project. Pin 3 V0 is connected to voltage Vcc through a variable resistor of 10k to adjust the contrast of LCD. ModelSim — How to force a struct type written in SystemVerilog? Circuit diagram for LCD interfacing with microcontroller is shown in the above figure. Antenna comes with the GSM module, you need to attach.
AT89S52 INTERFACING PDF
But there may a situation where we have to deal with external inputs such as analog signals. All most all the input signals from physical sensors are of analog signals. In such cases, we can interface the microcontroller with an external device such as an ADC to convert the analog signal to a digital signal. Because our microcontrollers can only understand 0 and 1.
ADC Interfacing with 8051