Add initial SPI code.

For now, add the following basic SPI functions:

 - spi_init_master()
 - spi_write()
 - spi_read()

This is incomplete and untested, yet.

Also, add some more SPI bit definition macros and comments.

lib/Makefile

@@ -27,7 +27,7 @@ CFLAGS		= -Os -g -Wall -Wextra -I../include -fno-common \
 		  -mcpu=cortex-m3 -mthumb -Wstrict-prototypes
 # ARFLAGS	= rcsv
 ARFLAGS		= rcs
-OBJS		= rcc.o gpio.o usart.o adc.o
+OBJS		= rcc.o gpio.o usart.o adc.o spi.o
 
 # Be silent per default, but 'make V=1' will show all compiler calls.
 ifneq ($(V),1)

lib/spi.c

@@ -0,0 +1,64 @@
+/*
+ * This file is part of the libopenstm32 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopenstm32.h>
+
+/*
+ * SPI and I2S code.
+ *
+ * Examples:
+ *  spi_init_master(SPI1, 1000000, SPI_CR1_CPOL_CLK_TO_0_WHEN_IDLE,
+ *                  SPI_CR1_CPHA_CLK_TRANSITION_1, SPI_CR1_DFF_8BIT,
+ *                  SPI_CR1_LSBFIRST);
+ *  spi_write(SPI1, 0x55);		// 8-bit write
+ *  spi_write(SPI1, 0xaa88);		// 16-bit write
+ *  reg8 = spi_read(SPI1);		// 8-bit read
+ *  reg16 = spi_read(SPI1);		// 16-bit read
+ */
+
+int spi_init_master(u32 spi, u32 br, u32 cpol, u32 cpha, u32 dff, u32 lsbfirst)
+{
+	u32 reg32 = 0;
+
+	reg32 |= br;       /* Set BAUD rate bits. */
+	reg32 |= cpol;     /* Set CPOL value. */
+	reg32 |= cpha;     /* Set CPHA value. */
+	reg32 |= dff;      /* Set data format (8 or 16 bits). */
+	reg32 |= lsbfirst; /* Set frame format (LSB-first or MSB-first). */
+
+	/* TODO: NSS pin handling. */
+
+	/* TODO: Set MSTR and SPE bits. */
+
+	SPI_CR1(spi) = reg32;
+
+	return 0; /* TODO */
+}
+
+void spi_write(u32 spi, u16 data)
+{
+	/* Write data (8 or 16 bits, depending on DFF) into DR. */
+	SPI_DR(spi) = data;
+}
+
+u16 spi_read(u32 spi)
+{
+	/* Read the data (8 or 16 bits, depending on DFF bit) from DR. */
+	return SPI_DR(spi);
+}