/*
 * Serial LPT driver module for Hitachi HD44780 based LCD displays by
 * Andrew McMeikan. The LCD is operated in it's 4 bit-mode through a
 * 4094 shift register and supports a keypad.
 *
 * Copyright (c)  1999 Andrew McMeikan <andrewm@engineer.com>
 *		  modular driver 1999 Benjamin Tse <blt@Comports.com> 
 *
 * Full connection details at http://members.xoom.com/andrewmuck/LCD.htm
 *
 * printer port	  4094/LCD
 * D2 (4)	  EN  (6 - LCD)
 * D3 (5)	  D   (2 - 4094)
 * D4 (6)	  CLK (3 - 4094)
 * +Vcc		  OE, STR (15, 1 - 4094)
 * D7 (9)	  EN2 (6 - LCD2) (optional)
 *
 * 4094		  LCD
 * Q1 (4)	  D4 (11)
 * Q2 (5)	  D5 (12)
 * Q3 (6)	  D6 (13)
 * Q4 (7)	  D7 (14)
 * Q6 (13)	  RS (4)
 * Gnd		  nRW (5)
 *
 * This file is released under the GNU General Public License. Refer to the
 * COPYING file distributed with this package.
 */

#include "hd44780-serialLpt.h"
#include "port.h"

// Hardware specific functions
void lcdserLpt_HD44780_senddata (unsigned char displayID, unsigned char flags, unsigned char ch);

static char lcdserLpt_HD44780_getkey (void);
void rawshift (unsigned char r);
void shiftreg (unsigned char displayID, unsigned char r);

#define RS	16
#define LCDDATA 8
#define LCDCLOCK 16
#define EN1	4
#define EN2	32

static unsigned int lp;
static char lastkey = 0;

// Initialisation
int
hd_init_serialLpt (HD44780_functions * hd44780_functions, lcd_logical_driver * driver, char *args, unsigned int port)
{
	int displayID = EN1 | EN2;

	lp = port;

	hd44780_functions->senddata = lcdserLpt_HD44780_senddata;

	// TODO: enable keypad only if specified on command line
	driver->getkey = lcdserLpt_HD44780_getkey;

	// setup the lcd in 4 bit mode
	shiftreg (displayID, 3);
	hd44780_functions->uPause (4100);

	shiftreg (displayID, 3);
	hd44780_functions->uPause (100);

	shiftreg (displayID, 3);
	hd44780_functions->uPause (40);

	shiftreg (displayID, 2);
	hd44780_functions->uPause (40);

	// set display type functions
	lcdserLpt_HD44780_senddata (0, RS_INSTR, FUNCSET | IF_4BIT | TWOLINE | SMALLCHAR);
	// clear
	lcdserLpt_HD44780_senddata (0, RS_INSTR, CLEAR);
	hd44780_functions->uPause (1600);
	// Now turn on the display
	lcdserLpt_HD44780_senddata (displayID, RS_INSTR, ONOFFCTRL | DISPON | CURSOROFF | CURSORNOBLINK);
	hd44780_functions->uPause (1600);

	return 0;
}

void
lcdserLpt_HD44780_senddata (unsigned char displayID, unsigned char flags, unsigned char ch)
{
	unsigned char dispID = 0, portControl = 0, h = ch >> 4, l = ch & 15;

	if (displayID == 1)
		dispID |= EN1;
	else if (displayID == 2)
		dispID |= EN2;
	else
		dispID |= EN1 | EN2;

	if (flags == RS_DATA)
		portControl = RS;
	else
		portControl = 0;

	shiftreg (displayID, flags | portControl | h);
	shiftreg (displayID, flags | portControl | l);

	/* TODO: instead of delay read keys here */
}

char
lcdserLpt_HD44780_getkey ()
{
	// TODO: a keypad scan that does not use shift register
	// define a key table 
	char keytr[] = "ABCDEFGH";
	int n;

	rawshift (0);					  //send all line on shift register low
	hd44780_functions->uPause (1);
	if ((port_in (lp + 1) & 32) == 0)	//test if line back is low - if not return(0)
	{									  //else 
		//start walking a single zero across the eight lines 
		for (n = 7; n >= 0; n--) {
			rawshift (255 - (1 << n));
			hd44780_functions->uPause (1);

			if ((port_in (lp + 1) & 32) == 0)	// check if line back is low if yes debounce 
			{
				if (lastkey == keytr[n])
					return (0);
				//      printf("key is %c %d\n",keytr[n],n);
				lastkey = keytr[n];
				return (keytr[n]);  //return correct key code.
			}
		}
	}									  //else fall out and return(0) [too transient a keypress]
	lastkey = 0;
	return (0);
}

/* this function sends r out onto the shift register */
void
rawshift (unsigned char r)
{
	int i;
	for (i = 7; i >= 0; i--) {	  /* MSB first      */
		port_out (lp, ((r >> i) & 1) * LCDDATA);	/*set up data   */
		port_out (lp, (((r >> i) & 1) * LCDDATA) | LCDCLOCK);	/*rising edge of clock   */
	}
}

// displayID = value on parallel port to toggle the correct display
void
shiftreg (unsigned char displayID, unsigned char r)
{
	rawshift (r);
	port_out (lp, displayID);	  //latch it, to correct display
	port_out (lp, 0);
}