如何在keil中观察c语言printf的结果?,STM32+Keil 如何使用printf函数？

Keil不支持Host-semi机制，即不支持直接在IDE打印字符串。

那么只能通过程序向硬件串口发数据了，这样调用的时候用自定义的函数即可，也很方便，例如：

void send_char_to_usart(unsigned char c){}

但是可否直接使用printf函数呢？毕竟人家都做好了，我们给他定一个打印输出的接口就可以了，答案是肯定的，看ST的官方源码：

/**

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

* @file Lib_DEBUG/Lib_DEBUG_Example/main.c

* @author MCD Application Team

* @version V1.1.1

* @date 13-April-2012

* @brief Main program body

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

* @attention

*

*

*

* Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");

* You may not use this file except in compliance with the License.

* You may obtain a copy of the License at:

*

* http://www.st.com/software_license_agreement_liberty_v2

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*

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

*/

/* Includes ------------------------------------------------------------------*/

#include "stm32l1xx.h"

#include "stm32l1xx_ip_dbg.h"

#include

#ifdef USE_STM32L152D_EVAL

#include "stm32l152d_eval.h"

#else

#include "stm32l152_eval.h"

#endif

/** @addtogroup STM32L1xx_StdPeriph_Examples

* @{

*/

/** @addtogroup Lib_DEBUG_Example

* @{

*/

/* Private typedef -----------------------------------------------------------*/

/* Private define ------------------------------------------------------------*/

/* Private macro -------------------------------------------------------------*/

/* Private variables ---------------------------------------------------------*/

USART_InitTypeDef USART_InitStructure;

/* Private function prototypes -----------------------------------------------*/

#ifdef __GNUC__

/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf

set to 'Yes') calls __io_putchar() */

#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)

#else

#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)

#endif /* __GNUC__ */

/* Private functions ---------------------------------------------------------*/

/**

* @brief Main program

* @param None

* @retval None

*/

int main(void)

{

/*!< At this stage the microcontroller clock setting is already configured,

this is done through SystemInit() function which is called from startup

file (startup_stm32l1xx_xx.s) before to branch to application main.

To reconfigure the default setting of SystemInit() function, refer to

system_stm32l1xx.c file

*/

GPIO_InitTypeDef GPIOA_InitStructure;

/* USARTx configured as follow:

- BaudRate = 115200 baud

- Word Length = 8 Bits

- One Stop Bit

- No parity

- Hardware flow control disabled (RTS and CTS signals)

- Receive and transmit enabled

*/

USART_InitStructure.USART_BaudRate = 115200;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

STM_EVAL_COMInit(COM1, &USART_InitStructure);

/* Initialize all peripherals pointers */

IP_Debug();

printf("rn STM32l1xx Firmware Library compiled with FULL ASSERT function... nr");

printf("...Run-time checking enabled nr");

/* Simulate wrong parameter passed to library function ---------------------*/

/* To enable SPI1 clock, RCC_APB2PeriphClockCmd function must be used and

not RCC_APB1PeriphClockCmd */

RCC_APB1PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

/* Some member of GPIOA_InitStructure structure are not initialized */

GPIOA_InitStructure.GPIO_Pin = GPIO_Pin_6;

GPIOA_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

/*GPIOA_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;*/

GPIOA_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIOA_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOA, &GPIOA_InitStructure);

while (1)

{

}

}

#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 can add his own implementation to report the file name and line number */

printf("nr Wrong parameter value detected onrn");

printf(" file %srn", file);

printf(" line %drn", line);

/* Infinite loop */

/* while (1)

{

} */

}

#endif

/**

* @brief Retargets the C library printf function to the USART.

* @param None

* @retval None

*/

PUTCHAR_PROTOTYPE

{

/* Place your implementation of fputc here */

/* e.g. write a character to the USART */

USART_SendData(EVAL_COM1, (uint8_t) ch);

/* Loop until the end of transmission */

while(USART_GetFlagStatus(EVAL_COM1, USART_FLAG_TC) == RESET)

{

}

return ch;

}

/**

* @}

*/

/**

* @}

*/

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/ 该例子就是把COM1作为输出口，把printf的数据打印到该串口上，因此你需要一个串口线与STM32和电脑相连，这样就可以看到printf了。