Question

1) Write an 8051 C program that will simulate a traffic light. Green will turn on for 2 seconds, Yellow for 1 second and Red for 2 seconds. The green, yellow and red LEDs are connected to Ports P11, P12 and P13.

2) Write an 8051 C program that will turn on or turn off an LED using a switch. The LED is connected to Port P15 while the switch is connected to Port P11.

Answer 1

solution:

1.

C program to simulate a traffic light :

Give :

Port P1.1 : connect Green LED

Port P1.2 : connect Yellow LED

Port P1.3 : connect Red LED

Delay : 2 sec for green , 1 sec for yellow , 2 sec for red

Code:

#include<reg51.h>

sbit greenLed=P1^1; //Led connected to port-1 pin#1

sbit yellowLed=P1^2; //Led connected to port-1 pin#2

sbit redLed=P1^3; //Led connected to port-1 pin#3

void delay()
{
int count=0;
while(count!=500)
{
   TMOD=0x01; //16-bit timer0 selected
   TH0=0xF8;   // Loading high byte in TH
   TL0=0xCC;   // Loaded low byte in TL
   TR0=1;      // Running the timer
    while(!TF0);   //Checking the timer flag register if it is not equal to 1
   TR0 = 0;      // If TF0=1 stop the timer
   TF0 = 0;      // Clear the Timer Flag bit for next calculation

   count++;
}

}

void main()
{
P1=0x00;   //Port-1 Declared Output

while(1)     // Constantly running while loop.
{
greenLed=1;    // Green LED glows here
yellowLed =0; //Yellow LED off
redLed = 0; // Red LED off

delay(); // Delay for 1 second
delay(); // Delay for 1 second

greenLed=0;    // Green LED off
yellowLed =1; //Yellow LED glows here
redLed = 0; // Red LED off

delay(); // Delay for 1 second

greenLed=0;    // Green LED off
yellowLed =0; //Yellow LED off
redLed = 1; // Red LED glows here

delay(); // Delay for 1 second
delay(); // Delay for 1 second

}
}

please give me thumb up