stm32 printf源码

以下是基于HAL库的STM32 printf源码示例：

#include "stm32f1xx_hal.h"
#include "stdio.h"

UART_HandleTypeDef huart1;

int __io_putchar(int ch)
{
    uint8_t c = ch;
    HAL_UART_Transmit(&huart1, &c, 1, HAL_MAX_DELAY);
    return ch;
}

void uart_init(void)
{
    huart1.Instance = USART1;
    huart1.Init.BaudRate = 115200;
    huart1.Init.WordLength = UART_WORDLENGTH_8B;
    huart1.Init.StopBits = UART_STOPBITS_1;
    huart1.Init.Parity = UART_PARITY_NONE;
    huart1.Init.Mode = UART_MODE_TX_RX;
    huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
    huart1.Init.OverSampling = UART_OVERSAMPLING_16;
    HAL_UART_Init(&huart1);
}

int main(void)
{
    HAL_Init();
    uart_init();
    printf("Hello, World!\r\n");
    while (1);
}

可以看到，首先需要包含STM32 HAL库和stdio.h头文件。然后定义一个`__io_putchar()`函数，该函数将字符发送到UART。接下来是初始化UART的函数`uart_init()`，其中定义了UART的一些参数。最后在`main()`函数中调用`printf()`来输出字符串。