/**********************************************************
- use 57600 bits/second
- every byte received will be sent back (except spaces in the query comand)
  even if it does not belong to any command
- commands are case sensitive
- 'r' will be sent to the host if a stepping is ready 
  (for commands sx,sy,Sx,Sy,ix,iy)

Commands:
   sx<hi><lo> : set position
   sy<hi><lo> : set position
   Sx<hi><lo> : set position (fast)
   Sy<hi><lo> : set position (fast)
   ix<hi><lo> : increment position
   iy<hi><lo> : increment position
   qx<space><space> : query position, <space> won't be sent back, <hi><lo> instead
   qy<space><space> : query position, <space> won't be sent back, <hi><lo> instead
   w<x> : set m*x*0.1ms wait time after a step
   n<m> : set m for wait time

***********************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <8052.h>

#define DLO  P0
#define DHI  P2
#define A1   P3_4
#define A2   P3_3
#define A3   P1_7
#define A4   P3_2
#define RST  P3_6
#define RDWR P3_5
#define STR  P3_7
#define LED  P1_5

static unsigned char dly_cycles=10;
unsigned current_x,current_y,desired_x,desired_y;
unsigned tmr2_i,tmr2_n;

void Delay(void)
{
	{
		_asm
			push b
			mov b,_dly_cycles
		00001$:
			djnz b,00001$
			pop b
		_endasm;
	}
}

void WaitStep()
{
	LED=0;
	tmr2_i=tmr2_n;
	while (tmr2_i);
	LED=1;
}

unsigned char SIn(void)
{
	while (!RI);
	RI=0;
	return SBUF;
}

void SOut(unsigned char a)
{
	while (!TI);
	TI=0;
	SBUF=a;
}

unsigned char SInOut(void)
{
	unsigned char c;
	while (!RI);
	RI=0;
	c=SBUF;
	while (!TI);
	TI=0;
	SBUF=c;
	return c;
}

void SInit()
{
	TH1=255; 	// 57600 baud
	PCON|=SMOD;	// set double baud rate
	TMOD=(TMOD & T0_MASK) | 0x20;	// timer 1 mode : 8-bit auto reload
	SCON=0x50;	// Set Serial for mode 1 & enable reception
	TR1=1;		// Start timer 1
	TI=1;           // ti is normally set in this program
	RI=0;           // ri is normally cleared
}

unsigned char Bitreverse(unsigned char x)
{
	unsigned char b,i;

	b=x & 1; 	// first bit of x
	for(i=0;i<7;i++) // seven shifts
	{
		x=x >> 1;
		b=(b << 1) + (x & 1);
	}
	return b;
}

void WriteX()
{
	DLO=current_x;
	DHI=Bitreverse(current_x>>8);
	A1=0;
	A2=1;
	RDWR=0;
	STR=0;
	Delay();
	STR=1;
	WaitStep();
}

void WriteY()
{
	DLO=current_y;
	DHI=Bitreverse(current_y>>8);
	A1=1;
	A2=0;
	RDWR=0;
	STR=0;
	Delay();
	STR=1;
	WaitStep();
}

void DoSteppingX()
{
	if (desired_x!=current_x)
	{
		if (desired_x>current_x)
		{
			while (current_x<desired_x)
			{
				current_x++;
				WriteX();
			}
		}
		else
		{
			while (current_x>desired_x)
			{
				current_x--;
				WriteX();
			}
		}
	}
	SOut('R');
}

void DoSteppingY()
{
	if (desired_y!=current_y)
	{
		if (desired_y>current_y)
		{
			while (current_y<desired_y)
			{
				current_y++;
				WriteY();
			}
		}
		else
		{
			while (current_y>desired_y)
			{
				current_y--;
				WriteY();
			}
		}
	}
	SOut('R');
}

void Reset()
{
	RST=0;
	Delay();
	RST=1;
}

void Timer2Init(unsigned tmr_n)
{
	EA=0;
	ET2=0;
	T2CON=0x0;
	RCAP2H=tmr_n>>8;
	RCAP2L=tmr_n;
	TH2=tmr_n>>8;
	TL2=tmr_n;
	EA=1;
	ET2=1;
	TR2=1;
}

void Timer2IRQ(void) interrupt 5
{
	TF2=0;
	if (tmr2_i) tmr2_i--;
}

void main(void)
{
	unsigned char c;
	unsigned d;
	unsigned char tmr2_step;

	LED=1;
	tmr2_n=100;
	tmr2_step=10;
	Timer2Init(65444); // 10kHz rate
	SInit(); 	// 57600
	RST=1;		// reset inactive
	current_x=32768;
	WriteX();	// default position
	current_y=32768;
	WriteY();
	while (1)
	{
		c=SInOut();
		if (c=='S') // set absolute position
		{
			c=SInOut();
			if (c=='x')
			{
				current_x=SInOut();
				current_x=(current_x << 8) + SInOut();
				WriteX();
				SOut('R');
			}
			else if (c=='y')
			{
				current_y=SInOut();
				current_y=(current_y << 8) + SInOut();
				WriteY();
				SOut('R');
			}
		}
		else if (c=='s')
		{
			c=SInOut();
			if (c=='x')
			{
				desired_x=SInOut();
				desired_x=(desired_x << 8) + SInOut();
				DoSteppingX();
			}
			else if (c=='y')
			{
				desired_y=SInOut();
				desired_y=(desired_y << 8) + SInOut();
				DoSteppingY();
			}
		}
		else if (c=='i') // increment position
		{
			c=SInOut();
			if (c=='x')
			{
				d=SInOut();
				d=(d << 8) + SInOut();
				if (d<32768) // positive step
				{
					if (65535-current_x>=d) desired_x=current_x+d;
					else desired_x=65535;
				}
				else // negative step
				{
					d=-d; // absolute value
					if (current_x>=d) desired_x=current_x-d;
					else desired_x=0;
				}
				DoSteppingX();
			}
			else if (c=='y')
			{
				d=SInOut();
				d=(d << 8) + SInOut();
				if (d<32768) // positive step
				{
					if (65535-current_y>=d) desired_y=current_y+d;
					else desired_y=65535;
				}
				else // negative step
				{
					d=-d; // absolute value
					if (current_y>=d) desired_y=current_y-d;
					else desired_y=0;
				}
				DoSteppingY();
			}
		}
		else if (c=='q')
		{
			c=SInOut();
			if (c=='x')
			{
				SIn();
				SOut(current_x>>8);
				SIn();
				SOut(current_x);
			}
			else if (c=='y')
			{
				SIn();
				SOut(current_y>>8);
				SIn();
				SOut(current_y);
			}
		}

		else if (c=='w')
		{
			tmr2_n=SInOut();
			if (tmr2_n==0) tmr2_n=1;
			tmr2_n*=tmr2_step; 			// resolution is tmr2_step*0.1millisec
		}
		else if (c=='n')
		{
			tmr2_step=SInOut();
			if (tmr2_step==0) tmr2_step=1;
		}
		else if (c=='r')
		{
			if (SInOut()=='s')
			{
				if (SInOut()=='t')
				{
					RST=0;
					Delay();
					RST=1;
					tmr2_step=10;
					tmr2_n=100; 				// resolution is 0.1millisec
				}
			}
		}
	}
}