7-segment has become the most popular display unit on market because it is cheap, easy to program and small. Nowadays they are used as displays in home appliances, cars, and various digital devices etc.
in the seven-segment displays, there are two types. Common anode and common cathode; in common anode all the anodes on the display are tied to a common pin, typically the power source, and the LED are controlled via the cathodes with ground being on and power being off. In common cathode all the cathodes are tied to a common pin, in this case generally ground, and the LED are driven by the state of the anodes where ground is off and power is on.
The 7 Segment figure shows a seven segment display and the names of the various segments.
In this article I will show you how to interface and use 7-Segment displays in your own projects.
Fundamentals of Seven-Segment Display
in the seven-segment displays, there are two types. Common anode and common cathode; in common anode all the anodes on the display are tied to a common pin, typically the power source, and the LED are controlled via the cathodes with ground being on and power being off. In common cathode all the cathodes are tied to a common pin, in this case generally ground, and the LED are driven by the state of the anodes where ground is off and power is on.
For example if you want to display number 4 then segments that will be ‘on’ are {f,g,b,c} while rest are ‘off’.Basically the seven segments are just LEDs.
7 Segment Display to Atmega8 Connection
Programming
#include <avr/io.h>
#include <util/delay.h>
//Configurations
//**************
// Here you may change the port in which you have connected the display
#define SEVEN_SEGMENT_PORT PORTD
#define SEVEN_SEGMENT_DDR DDRD
void SevenSegment(uint8_t n,uint8_t dp)
{
/*
This function writes a digit given by n to the display
the decimal point is displayed if dp=1
Note:
n must be less than 9
*/
if(n<10)
{
switch (n)
{
case 0:
SEVEN_SEGMENT_PORT=0b11000000;
break;
case 1:
//.gfedcba
SEVEN_SEGMENT_PORT=0b11111001;
break;
case 2:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10100100;
break;
case 3:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10110000;
break;
case 4:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10011001;
break;
case 5:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10010010;
break;
case 6:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10000010;
break;
case 7:
//.gfedcba
SEVEN_SEGMENT_PORT=0b11111000;
break;
case 8:
SEVEN_SEGMENT_PORT=0b10000000;
break;
case 9:
//.gfedcba
SEVEN_SEGMENT_PORT=0b10010000;
break;
}
if(dp)
{
//if decimal point should be displayed
//make 7th bit Low
SEVEN_SEGMENT_PORT&=0b01111111;
}
}
else
{
//This symbol on display tells that n was greater than 9
//so display can't handle it
SEVEN_SEGMENT_PORT=0b11111101;
}
}
void main()
{
//Setup io port direction as output
SEVEN_SEGMENT_DDR=0xFF; //All output
//turn off all leds
SEVEN_SEGMENT_PORT=0xFF; //All segments off
uint8_t count=0;
while(1)
{
SevenSegment(count,0);
count++;
if(count==10)
{
count=0;
}
_delay_ms(1000);
}
}
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