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 <dzu@denx.de>

1 files changed, 111 insertions, 0 deletions

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 <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;
+}