u-boot/drivers/twserial/soft_tws.c

/*
 * (C) Copyright 2009
 * Detlev Zundel, DENX Software Engineering, dzu@denx.de.
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 *
 */

#define TWS_IMPLEMENTATION
#include <common.h>

/*=====================================================================*/
/*                         Public Functions                            */
/*=====================================================================*/

/*-----------------------------------------------------------------------
 * Read bits
 */
int tws_read(uchar *buffer, int len)
{
	int rem = len;
	uchar accu, shift;

	debug("tws_read: buffer %p len %d\n", buffer, len);

	/* Configure the data pin for input */
	tws_data_config_output(0);

	/* Disable WR, i.e. setup a read */
	tws_wr(0);
	udelay(1);

	/* Rise CE */
	tws_ce(1);
	udelay(1);

	for (; rem > 0; ) {
		for (shift = 0, accu = 0;
		     (rem > 0) && (shift < 8);
		     rem--, shift++) {
			tws_clk(1);
			udelay(10);
			accu |= (tws_data_read() << shift); /* LSB first */
			tws_clk(0);
			udelay(10);
		}
		*buffer++ = accu;
	}

	/* Lower CE */
	tws_ce(0);

	return len - rem;
}


/*-----------------------------------------------------------------------
 * Write bits
 */
int tws_write(uchar *buffer, int len)
{
	int rem = len;
	uchar accu, shift;

	debug("tws_write: buffer %p len %d\n", buffer, len);

	/* Configure the data pin for output */
	tws_data_config_output(1);

	/* Enable WR, i.e. setup a write */
	tws_wr(1);
	udelay(1);

	/* Rise CE */
	tws_ce(1);
	udelay(1);

	for (; rem > 0; ) {
		for (shift = 0, accu = *buffer++;
		     (rem > 0) && (shift < 8);
		     rem--, shift++) {
			tws_data(accu & 0x01); /* LSB first */
			tws_clk(1);
			udelay(10);
			tws_clk(0);
			udelay(10);
			accu >>= 1;
		}
	}

	/* Lower CE */
	tws_ce(0);

	return len - rem;
}