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- What is 7-SEGMENT DISPLAY (SSD)? – A seven-segment display is a form of electronic display device for displaying decimal numbers (and some alphabets too). SSD may use a liquid crystal display (LCD), a light-emitting diode (LED) for each segment, or other light-generating or controlling techniques such as cold cathode gas discharge, vacuum fluorescent, incandescent filaments, and other.
- Types of SSD– There are mainly two types of SSD available. In a simple LED package, typically all of the cathodes (negative terminals) or all of the anodes (positive terminals) of the segment LEDs are connected and brought out to a common pin; this is referred to as a “common cathode” or “common anode” device. Besides this, there is also a SSD multiplexer is used called 2 digit, 3 digit and so on as you can see on photos.
- Operation – In a simple LED package common cathode SSD, there has 10 pin out of which 2 is ground and rest is LED segments . Particular LED segment is glow(ON) by giving logic ‘1’ to it and rests at logic ‘0’.
So we need to program this 8 pin to display our number on SSD. In following table, we convert this 8 pin’s 8 bit binary data into hex code and shows the hex code of displaying digits below.
| Digit | Hex code | A | B | C | D | E | F | G |
| 0 | 0x3F | 1 | 1 | 1 | 1 | 1 | 1 | 0 |
| 1 | 0x06 | 0 | 1 | 1 | 0 | 0 | 0 | 0 |
| 2 | 0x5B | 1 | 1 | 0 | 1 | 1 | 0 | 1 |
| 3 | 0x4F | 1 | 1 | 1 | 1 | 0 | 0 | 1 |
| 4 | 0x66 | 0 | 1 | 1 | 0 | 0 | 1 | 1 |
| 5 | 0x6D | 1 | 0 | 1 | 1 | 0 | 1 | 1 |
| 6 | 0x7D | 1 | 0 | 1 | 1 | 1 | 1 | 1 |
| 7 | 0x07 | 1 | 1 | 1 | 0 | 0 | 0 | 0 |
| 8 | 0x7F | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 9 | 0x6F | 1 | 1 | 1 | 1 | 0 | 1 | 1 |
- Applications- SSD is widely use in digital clocks, pricing menu at petrol pump, in metros and electronics meters as shown above.
1.Circuit Diagram of common cathode 7 segment display interfacing with ARM7 (LPC21XX)
1. Program Of 0 To 9 Counter On Cathode 7 segment display interfacing with ARM7 (LPC2148)
/******************************************************
IDE :- Keil
DEVELOPED BY:- FIRMWARE DEVELOPER (www.firmcodes.com)
WHAT PROGRAM DO:- COUNT 0 TO 9 ON 7 SEGMENT COMMON
CATHOD BY USING ARM(LPC21XX)
******************************************************/
#include<LPC21XX.H> // header file for lpc2148
void delay(); // delay function
unsigned int i,j,k; // globle variable
unsigned int ar[10]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90 }; // array data
int main()
{
PINSEL0=0X00000000; // select port0 as gpio mode
IO0DIR =0X000000FF; // make starting 8 pin as output and other as input of port0
while(1)
{
for(i=0;i<10;i++)
{
IO0SET =ar[i];
delay();
IO0CLR =ar[i];
}
}
return 0;
}
void delay()
{
for(j=0;j<1000;j++)
for(k=0;k<400;k++);
}
PROTEUS File for SIMULATION(Password Of RAR file is :-firmcodes.com)
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2. Program Of 000 To 999 Counter On Common Cathode 7 segment display interfacing with ARM7 (LPC2148)
/******************************************************
IDE : - Keil
DEVELOPED BY:- FIRMWARE DEVELOPER (www.firmcodes.com)
WHAT PROGRAM DO:- COUNT 000 TO 999 ON 7 SEGMENT COMMON
CATHODE USING ARM(LPC2148)
******************************************************/
#include<LPC21XX.H>
void delay();
int ar[10]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90 };
int ar1[10]={0xc000,0xf900,0xa400,0xb000,0x9900,0x9200,0x8200,0xf800,0x8000,0x9000 };
int ar2[10]={0xc00000,0xf90000,0xa40000,0xb00000,0x990000,0x920000,0x820000,0xf80000,0x800000,0x900000 };
int main()
{
unsigned int i,j,k;
PINSEL0=0X00000000;
IO0DIR =0Xffffffff;
while(1)
{
for(i=0;i<10;i++)
{
IO0SET =ar[i];
for(j=0;j<10;j++)
{
IO0SET =ar1[j];
for(k=0;k<10;k++)
{
IO0SET =ar2[k];
delay();
IO0CLR =ar2[k];
}
IO0CLR =ar1[j];
}
IO0CLR =ar[i];
}
}
return 0;
}
void delay()
{
unsigned int m,n;
for(m=0;m<500;m++)
for(n=0;n<1000;n++);
}
PROTEUS File for SIMULATION(Password Of RAR file is :-firmcodes.com)
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