Stopwatch using AT89S52 URGENT HELP REQUIRED

[sgtom]

Dear guys,


(C code below)


I have built this circuit (with AT89S52) but have the following problems:



Problem 1. (very important)

when I press the start and stop button.... the time jumps an extra second on the LED display. Is that coding problem? Please check the code.



Problem 2. (very important)

when i compare the time measurement to an actual stopwatch it seems to lag a few seconds behind (as in just press start on both at same time and compare time without stopping) Again coding problem?



Problem 3.



When powering up the circuit I have to switch the power supply on and off numerous times before I sucessfully get "0000" diplayed on led. Other wise i get random displays, no display, etc. any ideas why?




Question 1. (very important)

I would also like to display max 9 seconds and rest miliseconds accurately instead of current setup. any help on coding will be great!



Question 2.

How would I go about interfacing this cuircuit with my computer ( i need the recorded times displayed on comp too)



Question 4.

Can i connect 2 microcontrollers recording two sperate times to one port? If sO how do I do that?



Question 5.



Possible to have 1. start button, two sperate stops (with 2 separate led displays) on ONE mircocontroller?





THANK YOU SOO MUCH....



time and help greatly appreciated to any of help/ questions....



Look forward to hearing from you.



Thank you!

#include<reg51.h>
#define msec 1
unsigned int sec1,sec2;
int sec1_1,sec1_2,sec2_1,sec2_2;

unsigned int digi_val[10]={0x40,0xF9,0x24,0x30,0x19,0x12,0x02,0xF8,0x00,0x1 0};
sbit dig_ctrl_1=P1^0; // Declare the control pins of seven segments
sbit dig_ctrl_2=P1^1;
sbit dig_ctrl_3=P1^2;
sbit dig_ctrl_4=P1^3;
sbit start_pin = P1^4; // Start pin to start the watch.
sbit stop_pin = P1^5; // Stop pin to stop the watch.
sbit reset_pin = P1^6; // Reset pin to reset the watch.
int s,t;

void mplex_delay(unsigned int time) // Function to provide a time delay of approximatelty one second using Timer 1
{
int i,j;
for (i=0;i<=time;i++)
for(j=0;j<=50;j++);
}

void digi_out(unsigned int current_num)
{
P2=digi_val[current_num];
mplex_delay(msec);
}

void display(unsigned int dig1,unsigned int dig2) // Function to display the digits on seven segmnet. For more details refer seven segment multiplexing.
{
sec1_2=dig1%10;
sec1_1=dig1/10;
sec2_2=dig2%10;
sec2_1=dig2/10;
TMOD=0x01; //Enable Timer 0
TL0=0xFF;
TH0=0xDB;
TR0=1; // Triger Timer 0
while(TF0==0)
{
dig_ctrl_1 = 1;
dig_ctrl_2 = dig_ctrl_3 = dig_ctrl_4 = 0;
digi_out(sec1_1);
dig_ctrl_2 = 1;
dig_ctrl_1 = dig_ctrl_3 = dig_ctrl_4 = 0;
digi_out(sec1_2);
dig_ctrl_3 = 1;
dig_ctrl_2 = dig_ctrl_1 = dig_ctrl_4 = 0;
digi_out(sec2_1);
dig_ctrl_4 = 1;
dig_ctrl_2 = dig_ctrl_3 = dig_ctrl_1 = 0;
digi_out(sec2_2);
}

TR0=0;
TF0=0;
}

void main()
{
while(1)
{
start: // Segment to start the stop watch
start_pin = 1;
stop_pin = 1;
reset_pin = 1;
dig_ctrl_1 = 0;
dig_ctrl_2 = 0;
dig_ctrl_3 = 0;
dig_ctrl_4 = 0;
P2 = 0xFF;
s = t = 0;
while(start_pin == 1)// Check if start pin is pressed
{
display(0,0);
}

stopwatch: // Segment to stop the watch
for (sec1=s;sec1<=99;sec1++)
{
if (stop_pin == 0 ) //Check if stop pin is pressed
break;
for (sec2=t;sec2<=99; sec2++)
{
if (stop_pin == 0 ) //Check if stop pin is pressed
break;
t=0;
display(sec1,sec2);
}
}
stop_pin = 1;
s = sec1;
t = sec2;

while ( start_pin != 0 && reset_pin != 0 ) //Check if start pin or reset pins are not pressed
{
display(sec1,sec2);
}

if (start_pin == 0) //Check if start pin is pressed
{
goto stopwatch;
}
else
{
if (reset_pin == 0 ) //Check if reset pin is pressed
{
s = t = 0;
goto start;
}
}
}
}