/*
	stepper.c

	Stepper motor controller with serial interface.

	Copyright: Jeroen Vreeken (pe1rxq@amsat.org), 2000
	Published under the terms of the GNU Public License 2.0
	or any later version.

	This works well with sdcc under linux, any other compiler might
	not work at all!
*/

#include <reg51.h>
#include "wls.h"

#define LEFT	1
#define RIGHT	2
#define SWEEP	3
#define LEFT_SAFETY	P1_4
#define RIGHT_SAFETY	P1_5
#define OUTPUT_ENABLE	P1_6
#define PULSE_MASK	0xf0

/*******************************************************************************
    Global vars
*******************************************************************************/
/* Used to receive commands with rs232 */
unsigned char motor, command, cmddata;
unsigned char bytenr=0;
/* current rotating direction */
unsigned char direction=0;
/* number of steps to be taken (left_n and right_n) */
unsigned char n=0;
/* Are we executing the sweep command? */
unsigned char sweep=0;
/* Default speed */
unsigned char speed=250;
/* counter used for speed calculation */
unsigned char ticks=0;
/* used for shifting bits through */
unsigned char curpulse=1;
/* used when windows crashes ;-) */
unsigned char serialtimeout=0;
/* counter to prevent continous current */
unsigned char last_pulse;


/*******************************************************************************
    Interrupt routines 
*******************************************************************************/

void timer0_int (void) interrupt 1 using 1
{

	/* Ignore all received bytes after about 2 seconds*/
	serialtimeout++;
	if (!serialtimeout)
		bytenr=0;

	/* Switch of the driver after about 1/4 of a second */
	last_pulse--;
	if (!last_pulse) {
		OUTPUT_ENABLE=1;
	}

	/* invert P1.7, nice for debugging */
	P1 ^= 128;

	ticks++;
	if (!ticks) {
		ticks=speed;
		if (direction) {
			if (direction==LEFT && LEFT_SAFETY) {
				curpulse=curpulse << 1;
				if (curpulse > 8) {
					curpulse=1;
				} 
			} else if (RIGHT_SAFETY) {
				if (curpulse==1) {
					curpulse=8;
				} else {
					curpulse=curpulse >> 1;
				}
			}
			if (direction==LEFT && !LEFT_SAFETY) {
				if (sweep==SWEEP) {
					direction=RIGHT;
				} else {
					direction=0;
					n=0;
				}
			}
			if (direction==RIGHT && !RIGHT_SAFETY) {
				if (sweep==SWEEP) {
					direction=LEFT;
				} else {
					direction=0;
					n=0;
				}
			}
			if (n) {
				n--;
				if (!n) {
					direction=0;
				}
			}
		P1 &= PULSE_MASK;
		P1 |= curpulse;
		last_pulse=16;
		OUTPUT_ENABLE=0;
		}
	}

	return;
}

void serial_int (void) interrupt 4
{
	/* Did we receive data? */
	if (RI) {
		serialtimeout=0;
		RI=0;
		switch (bytenr) {
			case 0: {
				motor=SBUF;
				break;
			}
			case 1: {
				command=SBUF;
				break;
			} 
			case 2: {
				cmddata=SBUF;
				break;
			}
		}
		bytenr++;
		if (bytenr > 2) {
			bytenr=0;
			/* motornr should always be zero */
			if (!motor) {
				/* command handler */
				switch (command) {
					case COMMAND_LEFT_N: {
						n=cmddata;
						if (n)
							direction=LEFT;
						else
							direction=0;
						sweep=0;
						break;
					}
					case COMMAND_RIGHT_N: {
						n=cmddata;
						if (n)
							direction=RIGHT;
						else
							direction=0;
						sweep=0;
						break;
					}
					case COMMAND_LEFT: {
						direction=LEFT;
						n=0;
						sweep=LEFT;
						break;
					}
					case COMMAND_RIGHT: {
						direction=RIGHT;
						n=0;
						sweep=RIGHT;
						break;
					}
					case COMMAND_SWEEP: {
						if (!direction)
							direction=LEFT;
						sweep=SWEEP;
						n=0;
						break;
					}
					case COMMAND_STOP: {
						direction=0;
						sweep=0;
						n=0;
						break;
					}
					case COMMAND_SPEED: {
						speed=cmddata;
						if (ticks<speed)
							ticks=speed;
						break;
					}
					/* No need to do anything on STATUS */
				}
				/* Send status */
				while(!TI);
				TI=0;
				SBUF=
				    direction + 
				    STATUS_SAFETYL * (!LEFT_SAFETY) + 
				    STATUS_SAFETYR * (!RIGHT_SAFETY);
			}
		}
	}
}

/*******************************************************************************
    Main loop
*******************************************************************************/

void main (void)
{
	/* Set serial speed and mode */
	PCON |= 0x80;
	TH1 = TL1 = 250;
	TMOD &= 0x0f;	/* Set timer 1 */
	TMOD |= 0x20;	/* Set timer 1 as Gate=0 Timer, mode 2 */
	TR1 = 1;	/* Enable timer 1 */
	SCON = 0x40;	/* init port as 8-bit UART with variable baudrate */
	SCON |= 0x10;	/* Enabling serial reception*/
	SCON |= 0x02;	/* Setting TI bit */
	ES = 1;		/* Enable Serial interrupt*/
	
	TMOD &= 0xf0;	/* Set timer 0 */
	TMOD |= 0x00;	/* set timer 0 as Gate=0 Timer, mode 1 */
	TH0 = 255;	/* 225 -> 65311= 256*255 + 31 */
	TL0 = 64;
	TR0 = 1;	/* Enable timer 0 */
	ET0 = 1;	/* Enable timer 0 interrupt */
	
	EA=1;		/* Enable all enabled interrupts */
	
	/* Set some stuff right */
	P1 &= PULSE_MASK;
	OUTPUT_ENABLE=1;

	/* Say hello to the world */
	SBUF=
	    direction + 
	    STATUS_SAFETYL * (!LEFT_SAFETY) +
	    STATUS_SAFETYR * (!RIGHT_SAFETY);
	
	/* Go into an endless loop.... */
	while (1) {
	}
}