From 572e6179adb5447ff42ec2aa5cf3a26decf97583 Mon Sep 17 00:00:00 2001 From: Detlev Zundel Date: Mon, 30 Mar 2009 00:31:32 +0200 Subject: drivers/twserial: Add protocol driver for "three wire serial" interface. This pretty unintelligent interface is used on some RTC chips. Signed-off-by: Detlev Zundel --- drivers/twserial/soft_tws.c | 111 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 drivers/twserial/soft_tws.c (limited to 'drivers/twserial/soft_tws.c') diff --git a/drivers/twserial/soft_tws.c b/drivers/twserial/soft_tws.c new file mode 100644 index 0000000..0b50e1d --- /dev/null +++ b/drivers/twserial/soft_tws.c @@ -0,0 +1,111 @@ +/* + * (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 + +/*=====================================================================*/ +/* 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; +} -- cgit v1.1