最近把 MDK 升级到了 V5.25 ，发现 Managing Run-Time Environment 中已经有好多好多的库。相比之前已经好了太多太多，从底层驱动，到上层协议栈，常用的有不常用的也有。发现 ARM 对这套系统的更新速度加快了一些，觉得有必要学习一下。从驱动开始学起，先学 USART API 详细介绍见 CMSIS Driver USART API

USART 把收到的数据再发出去程序

/** 

  ****************************************************************************** 

  * @file    main.c 

  * @author  XinLi 

  * @version v1.0 

  * @date    20-March-2018 

  * @brief   Main program body. 

  ****************************************************************************** 

  * @attention 

  * 

  *

Copyright © 2018 XinLi

  * 

  * 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 . 

  * 

  ****************************************************************************** 

  */  

/* Header includes -----------------------------------------------------------*/  

#include "stm32f4xx.h"  

#include "Driver_USART.h"  

#include  

/* Macro definitions ---------------------------------------------------------*/  

/* Type definitions ----------------------------------------------------------*/  

/* Variable declarations -----------------------------------------------------*/  

extern ARM_DRIVER_USART Driver_USART1;  

/* Variable definitions ------------------------------------------------------*/  

static uint8_t rxBuffer[1024] = {0};  

static uint8_t txBuffer[1024] = {0};  

/* Function declarations -----------------------------------------------------*/  

static void USART1_Callback(uint32_t event);  

static void SystemClock_Config(void);  

/* Function definitions ------------------------------------------------------*/  

/** 

  * @brief  Main program. 

  * @param  None. 

  * @return None. 

  */  

int main(void)  

{  

  /* STM32F4xx HAL library initialization: 

       - Configure the Flash prefetch, instruction and Data caches 

       - Configure the Systick to generate an interrupt each 1 msec 

       - Set NVIC Group Priority to 4 

       - Global MSP (MCU Support Package) initialization 

     */  

  HAL_Init();  

  /* Configure the system clock to 168 MHz */  

  SystemClock_Config();  

  Driver_USART1.Initialize(USART1_Callback);  

  Driver_USART1.PowerControl(ARM_POWER_FULL);  

  Driver_USART1.Control(ARM_USART_MODE_ASYNCHRONOUS |  

                        ARM_USART_DATA_BITS_8 |  

                        ARM_USART_PARITY_NONE |  

                        ARM_USART_STOP_BITS_1 |  

                        ARM_USART_FLOW_CONTROL_NONE, 115200);  

  Driver_USART1.Control(ARM_USART_CONTROL_TX, 1);  

  Driver_USART1.Control(ARM_USART_CONTROL_RX, 1);  

  Driver_USART1.Receive(rxBuffer, sizeof(rxBuffer));  

  for(;;)  

  {  

  }  

}  

/** 

  * @brief  USART1 callback function. 

  * @param  event: USART events notification mask. 

  * @return None. 

  */  

static void USART1_Callback(uint32_t event)  

{  

  if(event & ARM_USART_EVENT_RX_TIMEOUT)  

  {  

    Driver_USART1.Control(ARM_USART_ABORT_RECEIVE, 1);  

    uint32_t length = Driver_USART1.GetRxCount();  

    memcpy(txBuffer, rxBuffer, length);  

    Driver_USART1.Send(txBuffer, length);  

    Driver_USART1.Receive(rxBuffer, sizeof(rxBuffer));  

  }  

}  

/** 

  * @brief  System Clock Configuration 

  *         The system Clock is configured as follow :  

  *            System Clock source            = PLL (HSE) 

  *            SYSCLK(Hz)                     = 168000000 

  *            HCLK(Hz)                       = 168000000 

  *            AHB Prescaler                  = 1 

  *            APB1 Prescaler                 = 4 

  *            APB2 Prescaler                 = 2 

  *            HSE Frequency(Hz)              = 8000000 

  *            PLL_M                          = 8 

  *            PLL_N                          = 336 

  *            PLL_P                          = 2 

  *            PLL_Q                          = 7 

  *            VDD(V)                         = 3.3 

  *            Main regulator output voltage  = Scale1 mode 

  *            Flash Latency(WS)              = 5 

  * @param  None 

  * @retval None 

  */  

static void SystemClock_Config(void)  

{  

  RCC_ClkInitTypeDef RCC_ClkInitStruct;  

  RCC_OscInitTypeDef RCC_OscInitStruct;  

  /* Enable Power Control clock */  

  __HAL_RCC_PWR_CLK_ENABLE();  

  /* The voltage scaling allows optimizing the power consumption when the device is  

     clocked below the maximum system frequency, to update the voltage scaling value  

     regarding system frequency refer to product datasheet.  */  

  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);  

  /* Enable HSE Oscillator and activate PLL with HSE as source */  

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;  

  RCC_OscInitStruct.HSEState = RCC_HSE_ON;  

  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;  

  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;  

  RCC_OscInitStruct.PLL.PLLM = 8;  

  RCC_OscInitStruct.PLL.PLLN = 336;  

  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;  

  RCC_OscInitStruct.PLL.PLLQ = 7;  

  HAL_RCC_OscConfig(&RCC_OscInitStruct);  

  /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2  

     clocks dividers */  

  RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);  

  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;  

  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;  

  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;    

  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;    

  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);  

  /* STM32F405x/407x/415x/417x Revision Z devices: prefetch is supported  */  

  if (HAL_GetREVID() == 0x1001)  

  {  

    /* Enable the Flash prefetch */  

    __HAL_FLASH_PREFETCH_BUFFER_ENABLE();  

  }  

}