Keil Setup For 8051 Revision as of 11:34, 17 December 2013 by Sandeep (Talk | contribs) (diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Seven Segment Display

fig 1: Basic 7 segment Display

fig 2: Simulation

Well, the name 7 segments implies there are 7 LED segments arranged as shown in figure 1. After LEDs they are the easiest interfaces to a microcontroller. There is also a decimal point or dp. It is used when decimal digits like 5.1 etc are displayed.

Applications

Seven segment are widely used in applications where digits[0-9] are required to be displayed.Although they also display letters A to F as shown in figure(2) simulation. This is a very simple and convenient way to display numbers in a bright fashion.

Form Factor

• Sizes:They come in various sizes; 0.28”, 0.3”, 0.32”, 0.36”, 0.39”, 0.4”, 0.5”, 0.56”, 0.6”, 0.8”, 1.0”, 1.2”, 1.5”, 1.8”, 2.0”, 2.3”, 3.0”, 4.0”, 5.0”, 7.0”)
• Colors: and varied colors too; Red, Green, Yellow, Orange, Blue, and White.

Working

fig 3:Common Cathode Display

fig 4: Common Anode 7 segment

Since these are basically LEDs arranged as a group they can either have anode in common or cathode.

• Common Cathode: This type of 7 segments, requires a positive voltage(5v) to given to the segments a to g in order to glow. This is shown in figure(3). Providing a positive voltage with respect to common cathode makes the LED forward biased.
• Common Anode: This type of 7 segments, requires a negativevoltage(GND) to given to the segments a to g in order to glow. This is shown in figure(4). A ground connection to cathode with respect to common anode again forward biases the LED which glows.
  

Interfacing 7 segment display to 8051

Schematic Diagram

Code

                                               
/* Reg51.h contains the defnition of all ports and SFRs */
#include <reg51.h>
#include "delay.h"      //User defined delay library which conatins the delay routines
#define SegmentValue P0
#define SegmentSelection P1
#define SegOne   0x01
#define SegTwo   0x02
#define SegThree 0x04
#define SegFour  0x08
/* start the main program */
void main()
{
 unsigned char seg_code[]=                                           {0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
   unsigned char cnt=0;
   while(1)
    {
           
            for(cnt=0x00;cnt<=0x0f;cnt++)        // loop to display 0-F
                 {
                        SegmentSelection = SegOne;       // Select the segment
                        SegmentValue= seg_code[cnt];     // Send code
                        delay_sec(1);
                  }

     }                                                                                           
}