#include<reg51.h>
sbit m1a = P1^1;//output 1(O1)
sbit m1b = P1^2;//output 2(O2)
sbit m2a = P1^3;//output 3(O3)
sbit m2b = P1^4;//output 4(O4)
void RXDATA(unsigned char);unsigned char RX(void);void MSDELAY(unsigned char);void A();void S();void D();void W();
void Z();void C();void U();void E();void Q();

void main( )
{
unsigned char a;
SCON=0X50;
TMOD=0X20;
TH1=-24;
TR1=1;
PCON=0X40;
P1=0X00;
	while(1)
	{	
	 a=RX();
	RXDATA(a);
	
	}
}

void RXDATA(unsigned char a)    //Receiving a byte data through serial port
{
 	switch(a)
 	{
		case('A'):
		 A( );
		break; 
			case('S'):
		 S( );
		break;
			case('D'):
		 D( );
		break;
			case('W'):
		 W( );
		break;
			case('Q'):
		 Q( );
		break;
			case('E'):
		 E( );
		break;
			case('U'):
		 U( );
		break;
			case('C'):
		 C( );
		break;
			case('Z'):
		 Z();
		break;
 	}
}


void D( )   //Right drifts 
{ 
unsigned char i;
P1=0;
m1a=1;
for(i=0;i<=9;i++)//PWM for 1/3 duty cycle
{
m2a=1;	
MSDELAY(15);
m2a=0;
MSDELAY(30);
}
P1=0;
}

void S( )  //Backward movement  
{
P1=0;
m1b=1;
m2b=1;
}

void A()  //Left drift 
{
unsigned char i;
P1=0;
m2a=1;
for(i=0;i<=9;i++)//PWM for 1/3 duty cycle
{
m1a=1;
MSDELAY(15);
m1a=0;
MSDELAY(30);
}
P1=0;
}

void W( )  //Forward movement 
{
P1=0;
m1a=1;
m2a=1;
}

void U()  //Stop
{
P1=0;
}

void E()  //Sharp forward right turn  
{
P1=0;
m1a=1;
}

void Q( )  //Sharp forward left turn   
{
P1=0;
m2a=1;
}

void Z( )  //Sharp backward right turn   
{
P1=0;
m2b=1;
}

void C()  //Sharp backward left turn 
{
P1=0;
m1b=1;
}

unsigned char  RX()	// Function to receive a data
{
	EMERGENCY:
	 RI=0;
	while(RI==0);
	if(SM0==1)//Check for framming error
	{
	SM0=0;
	goto EMERGENCY;
	}	 
	return(SBUF);
}

void MSDELAY(unsigned char b)  //Delay of 3.6Ms
{
unsigned char i;
unsigned int j;
for(i=0;i<=b;i++)
for(j=0;j<=310;j++);
}