DESCRIBTION(click here)
- A seven segment consists of eight LEDs which are aligned in a manner so as to display digits from 0 to 9 when proper combination of LED is switched on. Seven segment uses seven LED’s to display digits from 0 to 9 and the eighth LED is used for the dot. A typical seven segment looks like as shown in the figure below.
Seven Segment are available in two configuration - (1) Common Anode (2) Common Cathode.Here common anode seven segment display is used because the output current of the microcontroller is not sufficient enough to drive the LED’s, similar to the case of driving an LED. The circuit diagram shows the connections of seven segment to the controller. The pins a to g of the Seven Segment are connected to the Port P2 of the microcontroller. The common pin of the seven segment is connected to Vcc. The ‘h’ has not been used, which is the dot pin of the controller.Since the seven segment display works on negative logic, we will have to provide logic 0 to the corresponding pin to make an LED glow. Table below shows the hex values used to display the different digits.DIGITabcdefgHEX Value000000010x40110011110xF9200100100x24300001100x30410011000x19501001000x12601000000x02700011110xF8800000000x00900011000x10When the values corresponding to the digits 0 to 9 are given on the output port, the digit gets displayed on the seven segment.
CODE(click here)
// Program to interface single seven segment
#include<reg51.h>
delay_ms(int time) // Time delay function
{
int i,j;
for(i=0;i<time;i++)
for(j=0;j<1275;j++);
}
void main()
{
char num[]={0x40,0xF9,0x24,0x30,0x19,0x12,0x02,0xF8,0x00,0x10}; // Hex values corresponding to digits 0 to 9
int c;
while(1)
{
for(c=0;c<10;c++)
{
P2=num[c];
delay_ms(200);
}
}
}
