stm32:l0: enable usart peripheral

Now that the usart-v2 peripheral is extracted cleanly, adding it for l0
is very simple.

include/libopencm3/stm32/l0/usart.h

@@ -0,0 +1,49 @@
+/** @defgroup usart_defines USART Defines
+ *
+ * @brief <b>Defined Constants and Types for the STM32L0xx USART</b>
+ *
+ * @ingroup STM32L0xx_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
+
+/*
+ * 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/>.
+ */
+
+#ifndef LIBOPENCM3_USART_H
+#define LIBOPENCM3_USART_H
+
+#include <libopencm3/stm32/common/usart_common_all.h>
+#include <libopencm3/stm32/common/usart_common_v2.h>
+
+/** @defgroup usart_reg_base USART register base addresses
+ * @ingroup STM32F_usart_defines
+ * Holds all the U(S)ART peripherals supported.
+ * @{
+ */
+#define USART1				USART1_BASE
+#define USART2				USART2_BASE
+#define USART4				USART4_BASE
+#define USART5				USART5_BASE
+#define LPUART1				LPUART1_BASE
+/**@}*/
+
+BEGIN_DECLS
+
+END_DECLS
+
+#endif

include/libopencm3/stm32/usart.h

@@ -30,6 +30,8 @@
 #       include <libopencm3/stm32/f3/usart.h>
 #elif defined(STM32F4)
 #       include <libopencm3/stm32/f4/usart.h>
+#elif defined(STM32L0)
+#       include <libopencm3/stm32/l0/usart.h>
 #elif defined(STM32L1)
 #       include <libopencm3/stm32/l1/usart.h>
 #else