stm32uart单线半双工通信

/** ****************************************************************************** * @file system_stm32f1xx.c * @author MCD Application Team * @version V4.2.0 * @date 31-March-2017 * @brief CMSIS Cortex-M3 Device Peripheral Access Layer System Source File. * * 1. This file provides two functions and one global variable to be called from * user application: * - SystemInit(): Setups the system clock (System clock source, PLL Multiplier * factors, AHB/APBx prescalers and Flash settings). * This function is called at startup just after reset and * before branch to main program. This call is made inside * the "startup_stm32f1xx_xx.s" file. * * - SystemCoreClock variable: Contains the core clock (HCLK), it can be used * by the user application to setup the SysTick * timer or configure other parameters. * * - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must * be called whenever the core clock is changed * during program execution. * * 2. After each device reset the HSI (8 MHz) is used as system clock source. * Then SystemInit() function is called, in "startup_stm32f1xx_xx.s" file, to * configure the system clock before to branch to main program. * * 4. The default value of HSE crystal is set to 8 MHz (or 25 MHz, depending on * the product used), refer to "HSE_VALUE". * When HSE is used as system clock source, directly or through PLL, and you * are using different crystal you have to adapt the HSE value to your own * configuration. * ****************************************************************************** * @attention * * <h2><center>&copy; COPYRIGHT(c) 2017 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. * ****************************************************************************** */ /** @addtogroup CMSIS * @{ */ /** @addtogroup stm32f1xx_system * @{ */ /** @addtogroup STM32F1xx_System_Private_Includes * @{ */ #include "stm32f1xx.h" /** * @} */ /** @addtogroup STM32F1xx_System_Private_TypesDefinitions * @{ */ /** * @} */ /** @addtogroup STM32F1xx_System_Private_Defines * @{ */ #if !defined (HSE_VALUE) #define HSE_VALUE 8000000U /*!< Default value of the External oscillator in Hz. This value can be provided and adapted by the user application. */ #endif /* HSE_VALUE */ #if !defined (HSI_VALUE) #define HSI_VALUE 8000000U /*!< Default value of the Internal oscillator in Hz. This value can be provided and adapted by the user application. */ #endif /* HSI_VALUE */ /*!< Uncomment the following line if you need to use external SRAM */ #if defined(STM32F100xE) || defined(STM32F101xE) || defined(STM32F101xG) || defined(STM32F103xE) || defined(STM32F103xG) /* #define DATA_IN_ExtSRAM */ #endif /* STM32F100xE || STM32F101xE || STM32F101xG || STM32F103xE || STM32F103xG */ /*!< Uncomment the following line if you need to relocate your vector Table in Internal SRAM. */ /* #define VECT_TAB_SRAM */ #define VECT_TAB_OFFSET 0x00000000U /*!< Vector Table base offset field. This value must be a multiple of 0x200. */ /** * @} */ /** @addtogroup STM32F1xx_System_Private_Macros * @{ */ /** * @} */ /** @addtogroup STM32F1xx_System_Private_Variables * @{ */ /******************************************************************************* * Clock Definitions *******************************************************************************/ #if defined(STM32F100xB) ||defined(STM32F100xE) uint32_t SystemCoreClock = 24000000U; /*!< System Clock Frequency (Core Clock) */ #else /*!< HSI Selected as System Clock source */ uint32_t SystemCoreClock = 72000000U; /*!< System Clock Frequency (Core Clock) */ #endif const uint8_t AHBPrescTable[16U] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9}; const uint8_t APBPrescTable[8U] = {0, 0, 0, 0, 1, 2, 3, 4}; /** * @} */ /** @addtogroup STM32F1xx_System_Private_FunctionPrototypes * @{ */ #if defined(STM32F100xE) || defined(STM32F101xE) || defined(STM32F101xG) || defined(STM32F103xE) || defined(STM32F103xG) #ifdef DATA_IN_ExtSRAM static void SystemInit_ExtMemCtl(void); #endif /* DATA_IN_ExtSRAM */ #endif /* STM32F100xE || STM32F101xE || STM32F101xG || STM32F103xE || STM32F103xG */ /** * @} */ /** @addtogroup STM32F1xx_System_Private_Functions * @{ */ /** * @brief Setup the microcontroller system * Initialize the Embedded Flash Interface, the PLL and update the * SystemCoreClock variable. * @note This function should be used only after reset. * @param None * @retval None */ void SystemInit (void) { /* Reset the RCC clock configuration to the default reset state(for debug purpose) */ /* Set HSION bit */ RCC->CR |= 0x00000001U; /* Reset SW, HPRE, PPRE1, PPRE2, ADCPRE and MCO bits */ #if !defined(STM32F105xC) && !defined(STM32F107xC) RCC->CFGR &= 0xF8FF0000U; #else RCC->CFGR &= 0xF0FF0000U; #endif /* STM32F105xC */ /* Reset HSEON, CSSON and PLLON bits */ RCC->CR &= 0xFEF6FFFFU; /* Reset HSEBYP bit */ RCC->CR &= 0xFFFBFFFFU; /* Reset PLLSRC, PLLXTPRE, PLLMUL and USBPRE/OTGFSPRE bits */ RCC->CFGR &= 0xFF80FFFFU; #if defined(STM32F105xC) || defined(STM32F107xC) /* Reset PLL2ON and PLL3ON bits */ RCC->CR &= 0xEBFFFFFFU; /* Disable all interrupts and clear pending bits */ RCC->CIR = 0x00FF0000U; /* Reset CFGR2 register */ RCC->CFGR2 = 0x00000000U; #elif defined(STM32F100xB) || defined(STM32F100xE) /* Disable all interrupts and clear pending bits */ RCC->CIR = 0x009F0000U; /* Reset CFGR2 register */ RCC->CFGR2 = 0x00000000U; #else /* Disable all interrupts and clear pending bits */ RCC->CIR = 0x009F0000U; #endif /* STM32F105xC */ #i