stm32F407下printf重定向到串口
前面学会了使用通过串口发送和接收数据.。
本例程使用stm32的官方推荐HAL库和STM32CubeIDE作为开发工具
在没有J-link等调试器的情况下，可以通过串口打印日志实现简单的调试功能，想必大家在平时练习的时候，经常会使用printf来打印日志。但是每次通过usart函数通过串口发送数据，实在是太麻烦。因此将printf输出重定向至串口，即可在电脑上通过串口接收工具了解打印信息。
硬件
本例程启用uart1串口，根据开发板，uart1是复用了PA9和PA10两个引脚
同时加了两个LED灯作为指示灯
- LED7<-->PF7：作为指示灯，开发板上电后常亮
- LED8<-->PF8：发送消息时闪烁
- USART1_TX<-->PA9：USART1的发送引脚，与PA9复用
- USART1_RX<-->PA10：USART1的接收引脚，与PA10服用
原理
如何实现，网上的例程很多，我也是抄网上的方法^_^
大概思路是通过宏定义，将输出函数用一个HAL库的HAL_UART_Transmit函数替代，原理代码如下：
#ifdef __GNUC__
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif
PUTCHAR_PROTOTYPE
{
//这里使用uart1串口
HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xffff);
return ch;
}
实现
本例程目标简单，实现代码全部在main.c文件中
导入stdio.h
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
/* USER CODE END Includes */
重定向printf
/* USER CODE BEGIN PFP */
#ifdef __GNUC__
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif
PUTCHAR_PROTOTYPE
{
//使用uart1端口
HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xffff);
return ch;
}
/* USER CODE END PFP */
使用printf
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
led8_switch();
printf("tx=%s\r\n",tx_array);
printf("output float k=%.1f\r\n",k);
HAL_Delay(200);
// HAL_UART_Transmit(&huart1, tx_array, sizeof(tx_array), 10000);
}
/* USER CODE END 3 */
输出结果为
注：这里float输出有问题，解决方法见下面
tx=bytetoy,goodluck!
output float k=
tx=bytetoy,goodluck!
output float k=
tx=bytetoy,goodluck!
output float k=
完整代码
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2022 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usart.h"
#include "gpio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
#ifdef __GNUC__
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif
PUTCHAR_PROTOTYPE
{
//具体哪个串口可以更改huart1为其它串�????
HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xffff);
return ch;
}
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
#define led7_on() HAL_GPIO_WritePin(GPIOF, GPIO_PIN_7, GPIO_PIN_SET)
#define led7_off() HAL_GPIO_WritePin(GPIOF, GPIO_PIN_7, GPIO_PIN_RESET)
#define led7_switch() HAL_GPIO_TogglePin(GPIOF, GPIO_PIN_7)
#define led8_on() HAL_GPIO_WritePin(GPIOF, GPIO_PIN_8, GPIO_PIN_SET)
#define led8_off() HAL_GPIO_WritePin(GPIOF, GPIO_PIN_8, GPIO_PIN_RESET)
#define led8_switch() HAL_GPIO_TogglePin(GPIOF, GPIO_PIN_8)
uint8_t tx=1;
uint8_t tx_array[]="bytetoy,goodluck!";
float k=1.2;
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
led7_on();
led8_on();
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USART1_UART_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
led8_switch();
printf("tx=%s\r\n",tx_array);
printf("output float k=%.1f\r\n",k);
HAL_Delay(200);
// HAL_UART_Transmit(&huart1, tx_array, sizeof(tx_array), 10000);
}
/* USER CODE END 3 */
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Configure the main internal regulator output voltage
*/
__HAL_RCC_PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
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 = 4;
RCC_OscInitStruct.PLL.PLLN = 168;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 4;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|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;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
{
Error_Handler();
}
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
碰到的问题
无法输出浮点数(float)
我用的开发环境是STM32CubeIDE，需要对项目进行一个配置
project->properties->C/C++Build->Settings->Tool Settings->MCU Settings->Use float with printf from newlib-nano(勾选此选项)
配置后输出内容正常
tx=bytetoy,goodluck!
output float k=1.2
tx=bytetoy,goodluck!
output float k=1.2
tx=bytetoy,goodluck!
output float k=1.2
tx=bytetoy,goodluck!
output float k=1.2
输出内容乱码
输出内容在串口调试工具上显示乱码，原因很多，我碰到的主要两个原因
修改波特率
将代码波特率和串口调试工具的波特率均调为9600，波特率太高了，貌似有点问题，有可能是我的数据线质量太差；
重定向的代码
关键代码是一次发送一个字节，不能修改为其他数字
HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xffff);
重要提醒
重定向要在printf使用之前完成定义，因此强烈建议按照放在例程所在的位置。
注意时钟
有个把月没有继续学这个了，配置的时候犯了一个低级又致命的错误，就是外部时钟配置错了。开发板搭载的外部时钟是8M的晶振，因此配置的时候务必改为8（默认是25）