diff --git a/lib/Makefile b/lib/Makefile
index e2d0e280..2bc31a28 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -27,7 +27,7 @@ CFLAGS		= -Os -g -Wall -Wextra -I../include -fno-common \
 		  -mcpu=cortex-m3 -mthumb
 # ARFLAGS	= rcsv
 ARFLAGS		= rcs
-OBJS		= gpio.o
+OBJS		= gpio.o rcc.o
 
 # Be silent per default, but 'make V=1' will show all compiler calls.
 ifneq ($(V),1)
diff --git a/lib/rcc.c b/lib/rcc.c
new file mode 100644
index 00000000..5f100939
--- /dev/null
+++ b/lib/rcc.c
@@ -0,0 +1,212 @@
+/*
+ * This file is part of the libopenstm32 project.
+ *
+ * Copyright (C) 2009 Federico Ruiz-Ugalde <memeruiz at gmail dot com>
+ * 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"
+
+void rcc_osc_ready_int_clear(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		RCC_CR |= PLLRDYC;
+		break;
+	case HSE:
+		RCC_CR |= HSERDYC;
+		break;
+	case HSI:
+		RCC_CR |= HSIRDYC;
+		break;
+	case LSE:
+		RCC_CIR |= LSERDYC;
+		break;
+	case LSI:
+		RCC_CIR |= LSIRDYC;
+		break;
+	}
+}
+
+void rcc_osc_ready_int_enable(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		RCC_CR |= PLLRDYIE;
+		break;
+	case HSE:
+		RCC_CR |= HSERDYIE;
+		break;
+	case HSI:
+		RCC_CR |= HSIRDYIE;
+		break;
+	case LSE:
+		RCC_CIR |= LSERDYIE;
+		break;
+	case LSI:
+		RCC_CIR |= LSIRDYIE;
+		break;
+	}
+}
+
+void rcc_osc_ready_int_disable(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		RCC_CR &= ~PLLRDYIE;
+		break;
+	case HSE:
+		RCC_CR &= ~HSERDYIE;
+		break;
+	case HSI:
+		RCC_CR &= ~HSIRDYIE;
+		break;
+	case LSE:
+		RCC_CIR &= ~LSERDYIE;
+		break;
+	case LSI:
+		RCC_CIR &= ~LSIRDYIE;
+		break;
+	}
+}
+
+int rcc_osc_ready_int_flag(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		return ((RCC_CR & PLLRDYF) != 0);
+		break;
+	case HSE:
+		return ((RCC_CR & HSERDYF) != 0);
+		break;
+	case HSI:
+		return ((RCC_CR & HSIRDYF) != 0);
+		break;
+	case LSE:
+		return ((RCC_CIR & LSERDYF) != 0);
+		break;
+	case LSI:
+		return ((RCC_CIR & LSIRDYF) != 0);
+		break;
+	}
+}
+
+void rcc_css_int_clear(void)
+{
+	RCC_CIR |= CSSC;
+}
+
+int rcc_css_int_flag(void)
+{
+	return ((RCC_CIR & CSSF) != 0);
+}
+
+int rcc_osc_ready(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		return ((RCC_CR & PLLRDY) != 0);
+		break;
+	case HSE:
+		return ((RCC_CR & HSERDY) != 0);
+		break;
+	case HSI:
+		return ((RCC_CR & HSIRDY) != 0);
+		break;
+	case LSE:
+		return ((RCC_BDCR & LSERDY) != 0);
+		break;
+	case LSI:
+		return ((RCC_CSR & LSIRDY) != 0);
+		break;
+	}
+}
+
+void rcc_osc_on(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		RCC_CR |= PLLON;
+		break;
+	case HSE:
+		RCC_CR |= HSEON;
+		break;
+	case HSI:
+		RCC_CR |= HSION;
+		break;
+	case LSE:
+		RCC_BDCR |= LSEON;
+		break;
+	case LSI:
+		RCC_CSR |= LSION;
+		break;
+	}
+}
+
+void rcc_osc_off(osc_t osc)
+{
+	switch (osc) {
+	case PLL:
+		RCC_CR &= ~PLLON;
+		break;
+	case HSE:
+		RCC_CR &= ~HSEON;
+		break;
+	case HSI:
+		RCC_CR &= ~HSION;
+		break;
+	case LSE:
+		RCC_BDCR &= ~LSEON;
+		break;
+	case LSI:
+		RCC_CSR &= ~LSION;
+		break;
+	}
+}
+
+void rcc_css_enable(void)
+{
+	RCC_CR |= CSSON;
+}
+
+void rcc_css_disable(void)
+{
+	RCC_CR &= ~CSSON;
+}
+
+void rcc_osc_bypass_enable(osc_t osc)
+{
+	switch (osc) {
+	case HSE:
+		RCC_CR |= HSEBYP;
+		break;
+	case LSE:
+		RCC_BDCR |= LSEBYP;
+		break;
+	}
+}
+
+void rcc_osc_bypass_disable(osc_t osc)
+{
+	switch (osc) {
+	case HSE:
+		RCC_CR &= ~HSEBYP;
+		break;
+	case LSE:
+		RCC_BDCR &= ~LSEBYP;
+		break;
+	}
+}