[stm32] Support the "new" BCD style RTC peripheral

Add the register definitions and some of the most basic helper functions
for the new style BCD RTC module found on the F2, F4, L1, F3 and F0.

This tries to keep as close to HACKING_COMMON_DOC as possible, while
maintaining sane names.

lib/stm32/common/rtc_common_bcd.c

@@ -0,0 +1,78 @@
+/** @addtogroup rtc_file */
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2012 Karl Palsson <karlp@tweak.net.au>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**@{*/
+
+#include <libopencm3/stm32/rtc.h>
+
+/*---------------------------------------------------------------------------*/
+/** @brief Set RTC prescalars.
+
+This sets the RTC synchronous and asynchronous prescalars.
+*/
+
+void rtc_set_prescaler(u32 sync, u32 async) {
+	/*
+	 * Even if only one of the two fields needs to be changed,
+	 * 2 separate write accesses must be performed to the RTC_PRER register.
+	 */
+	RTC_PRER = (sync & RTC_PRER_PREDIV_S_MASK);
+	RTC_PRER |= (async << RTC_PRER_PREDIV_A_SHIFT);
+}
+
+/*---------------------------------------------------------------------------*/
+/** @brief Wait for RTC registers to be synchronised with the APB1 bus
+
+ Time and Date are accessed through shadow registers which must be synchronized
+*/
+
+void rtc_wait_for_synchro(void) {
+	/* Unlock RTC registers */
+	RTC_WPR = 0xca;
+	RTC_WPR = 0x53;
+
+	RTC_ISR &= ~(RTC_ISR_RSF);
+
+	while (!(RTC_ISR & RTC_ISR_RSF)) {
+		;
+	}
+	/* disable write protection again */
+	RTC_WPR = 0xff;
+}
+
+/*---------------------------------------------------------------------------*/
+/** @brief Unlock write access to the RTC registers
+
+*/
+void rtc_unlock(void) {
+	RTC_WPR = 0xca;
+	RTC_WPR = 0x53;
+}
+
+/*---------------------------------------------------------------------------*/
+/** @brief Lock write access to the RTC registers
+
+*/
+void rtc_lock(void) {
+	RTC_WPR = 0xff;
+}
+
+/**@}*/

lib/stm32/f2/Makefile

@@ -31,7 +31,8 @@ ARFLAGS		= rcs
 OBJS		= rcc.o gpio.o flash.o exti2.o timer.o \
 		  gpio_common_all.o gpio_common_f24.o dma_common_f24.o spi_common_all.o \
 		  dac_common_all.o usart_common_all.o iwdg_common_all.o i2c_common_all.o \
-		  crc_common_all.o
+		  crc_common_all.o \
+		  rtc_common_bcd.o
 
 VPATH += ../../usb:../:../../cm3:../common
 

lib/stm32/f2/rtc.c

@@ -0,0 +1,27 @@
+/** @defgroup rtc_file RTC
+
+@ingroup STM32F2xx
+
+@brief <b>libopencm3 STM32F2xx RTC</b>
+
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/stm32/rtc.h>
+#include <libopencm3/stm32/common/rtc_common_bcd.h>

lib/stm32/f4/Makefile

@@ -35,7 +35,8 @@ OBJS		= rcc.o gpio.o flash.o exti2.o pwr.o timer.o \
 		  pwr_common_all.o \
 		  gpio_common_all.o gpio_common_f24.o dma_common_f24.o spi_common_all.o \
 		  dac_common_all.o usart_common_all.o iwdg_common_all.o i2c_common_all.o \
-		  crc_common_all.o
+		  crc_common_all.o \
+		  rtc_common_bcd.o
 
 VPATH += ../../usb:../:../../cm3:../common
 

lib/stm32/f4/rtc.c

@@ -0,0 +1,27 @@
+/** @defgroup rtc_file RTC
+
+@ingroup STM32F4xx
+
+@brief <b>libopencm3 STM32F4xx RTC</b>
+
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/stm32/rtc.h>
+#include <libopencm3/stm32/common/rtc_common_bcd.h>

lib/stm32/l1/Makefile

@@ -32,6 +32,7 @@ OBJS		= rcc.o desig.o crc.o usart.o exti2.o flash.o timer.o
 OBJS +=     gpio_common_all.o gpio_common_f24.o spi_common_all.o crc_common_all.o
 OBJS +=     dac_common_all.o usart_common_all.o iwdg_common_all.o i2c_common_all.o
 OBJS +=     pwr_common_all.o pwr.o
+OBJS +=     rtc_common_bcd.o
 
 VPATH += ../../usb:../:../../cm3:../common
 

lib/stm32/l1/rtc.c

@@ -0,0 +1,27 @@
+/** @defgroup rtc_file RTC
+
+@ingroup STM32L1xx
+
+@brief <b>libopencm3 STM32L1xx RTC</b>
+
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/stm32/rtc.h>
+#include <libopencm3/stm32/common/rtc_common_bcd.h>