Add STM32F103 port

Add a fully functional STM32F1 port, currently mostly targeting STM32F103
microcontrollers. This requires an 8 MHz XTAL. The maximum possible step rate
is around 282K steps per second.

This uses stm32flash to burn the firmware. The bootloader needs to be started
by setting BOOT0 to 1 and resetting the MCU. There is no automatic bootloader,
unlike on Arduino.

Signed-off-by: Grigori Goronzy <greg@kinoho.net>

lib/hal-stm32f1/source/stm32f1xx_ll_pwr.c

@@ -0,0 +1,103 @@
+/**
+  ******************************************************************************
+  * @file    stm32f1xx_ll_pwr.c
+  * @author  MCD Application Team
+  * @version V1.1.1
+  * @date    12-May-2017
+  * @brief   PWR LL module driver.
+  ******************************************************************************
+  * @attention
+  *
+  * <h2><center>&copy; COPYRIGHT(c) 2016 STMicroelectronics</center></h2>
+  *
+  * Redistribution and use in source and binary forms, with or without modification,
+  * are permitted provided that the following conditions are met:
+  *   1. Redistributions of source code must retain the above copyright notice,
+  *      this list of conditions and the following disclaimer.
+  *   2. Redistributions in binary form must reproduce the above copyright notice,
+  *      this list of conditions and the following disclaimer in the documentation
+  *      and/or other materials provided with the distribution.
+  *   3. Neither the name of STMicroelectronics nor the names of its contributors
+  *      may be used to endorse or promote products derived from this software
+  *      without specific prior written permission.
+  *
+  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  *
+  ******************************************************************************
+  */
+#if defined(USE_FULL_LL_DRIVER)
+
+/* Includes ------------------------------------------------------------------*/
+#include "stm32f1xx_ll_pwr.h"
+#include "stm32f1xx_ll_bus.h"
+
+/** @addtogroup STM32F1xx_LL_Driver
+  * @{
+  */
+
+#if defined(PWR)
+
+/** @defgroup PWR_LL PWR
+  * @{
+  */
+
+/* Private types -------------------------------------------------------------*/
+/* Private variables ---------------------------------------------------------*/
+/* Private constants ---------------------------------------------------------*/
+/* Private macros ------------------------------------------------------------*/
+/* Private function prototypes -----------------------------------------------*/
+
+/* Exported functions --------------------------------------------------------*/
+/** @addtogroup PWR_LL_Exported_Functions
+  * @{
+  */
+
+/** @addtogroup PWR_LL_EF_Init
+  * @{
+  */
+
+/**
+  * @brief  De-initialize the PWR registers to their default reset values.
+  * @retval An ErrorStatus enumeration value:
+  *          - SUCCESS: PWR registers are de-initialized
+  *          - ERROR: not applicable
+  */
+ErrorStatus LL_PWR_DeInit(void)
+{
+  /* Force reset of PWR clock */
+  LL_APB1_GRP1_ForceReset(LL_APB1_GRP1_PERIPH_PWR);
+
+  /* Release reset of PWR clock */
+  LL_APB1_GRP1_ReleaseReset(LL_APB1_GRP1_PERIPH_PWR);
+
+  return SUCCESS;
+}
+
+/**
+  * @}
+  */
+
+/**
+  * @}
+  */
+
+/**
+  * @}
+  */
+#endif /* defined(PWR) */
+/**
+  * @}
+  */
+
+#endif /* USE_FULL_LL_DRIVER */
+
+/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/