LED Seven Segment Displays Interface with PIC16f84

These tutorials demonstrate how to use a multiplexed 7 segment LED displays. The digit of a seven segment display basically contains seven LEDs built in. As in the fig below it is cleared that the LEDs have two legs for its operation.

Then each seven segment display one leg of all the LEDs is connected together and it is called common wire or electrode. The other legs are used to operate the LED individually. As shown in the fig below.

Types of the LED Display:

As it is shown above there are many types of LED displays, some very common are shown above.

By functionality point of view and keeping in view our tutorial on led display, we can easily classified these in two:

Common anode type and Common Cathode type displays.

The box that the 7 segment is in represents the common. There are two types of 7 segment displays, common cathode and common anode. In my projects, I use common cathode displays. As you can see, to control any of the segments, a +ve signal is required, as they all share the same earth. So these are common cathode type displays.

Interface of one seven segment display with microcontroller PIC16f84.


Components used:

LED Seven Segment display common cathode type (one)

Microcontroller PIC16f84 (one)

Resistors: 220Ohm (seven)

Crystal : 4 MHz (One)

Capacitors: 33pf (two)

Power supply: % volt Dc regulated power supply (One)

FIG (interface of one digit with microcontroller)

Program:

The program for display is written in Proton Basic language.

The code listing is as follows. The whole code is commented well, to describe the reasoning of each line.

The following example shows how to decode a value between 0-9 into 7 segment data and display it.

Xtal = 4
Dim N As Byte

Initialization:

PORTB_PULLUPS = False ‘internal pull up are switched off.

dim number [10] as byte ‘ this declaration of an array of 10 bytes with name number. Dim is reserved word for proton compiler, and number is the name of the array you can use your own name whatever you like but it should not be from the reserved word of compiler.


number [0] = 111111 ‘ here we do the initialization of the element of the array with known numbers so that a meaning full display comes on the digit. This number depends on the hardware connection very much.

number [1] = 000110

number [2] = %01011011

number [3] = %01001111

number [4] = %01100110

number [5] = %01101101

number [6] = %01111100

number [7] = 000111

number [8] = %01111111

number [9] = %01100111 ‘ the index of the array is the number to be display on the digit. And each element is filled with the binary code of that number.

TRISB = 000000 ' Make PORTB all outputs
Main:

N = 0 initially the counter is zero

Repeat ' Create a loop

PORTB = number [N] ' Convert to segment data and display it

DelaymS 500 ' Small delay to slow down counting

Inc N ' Increment the Number register

Until N = 10 ' Loop until number = 10, then reset

GoTo Main ' Loop forever

Stop

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