Exact Circuit and MicroC code for stepper motor

Well saw that people still are having quite some doubts on the stepper motor post that i had put up. so i thot to make that abstact clear i better put the exact circuit and the code here.

The exact circuit to connect the stepper motor to 16F877A is given below

In this the common is connected to the 16V supply(12 v is actually enough actually higher current drives the motor better as far as i know*). If u are new here and donot know how to find the common line in a unipolar Stepper motor then see here

The MicroC code for running the motor is as below.
void main()
{
TRISB = 0x00;
PORTB = 0x00;

//routine to move in one direction
for (i=0;i<50;i++)// increse i=50 no i=100 to cover double the distance
{
PORTB=0x80;
delay(20ms);
PORTB=0x40;
delay(20ms);
PORTB=0x20;
delay(20ms);
PORTB=0x10;
delay(20ms);
}

//routine to move in the other direction

for (i=0;i<50;i++) // increse i=50 no i=100 to cover double the distance
{
PORTB=0x10;
delay(20ms);
PORTB=0x20;
delay(20ms);
PORTB=0x40;
delay(20ms);
PORTB=0x80;
delay(20ms);
}
}

There are much easier ways to write the above code but then i am not worried about the memory it’l take nor have any pressing need to keep my code small and trim ,so i guess this will make you absolutely clear of what i’m trying to do to make my motor run.

If you din know MicroC well,let me brief. The line PORTB = 0x80 (1000000)makes my 8th pin of the PORT “B” that’s b7 pin or the 40th pin go high.The next line PORTB = 0x40(01000000) will make the 39th pin go high and all other low.

Now whenever the pin at the input of the ULN2003 goes high say pin 1 the output pin 16 drains the current throuh the motor thus completing the circuit from supplt 16V through motor to the ground in that line. When you keep doing this in series as i called it the abcd pulse the motor will rotate . When your reverse the pulse order the motor rotates in the other direction. As simple as that. For most robotic application atleast at contest level you may use this circuit uinless you go for bigger stepper motors that need more current to drive and is greater than the 500mA that the ULN2003 can sink!!
i guess i was clear about using ULN2003 to drive a sstepper motor. pl post your comments and doubts
–Madan
I like keeping all my circuits small and simple and not crowd it with resistors and capacitors.Afterall its a hobby and we need not complicate it.Cheers.