STM32初始化串口重定向后printf调试信息不输出的难题

STM32初始化串口重定向后调试信息不输出的问题

@@ Author：明月清了个风

@@ Date： 2025/9/9

@@ PS：开发stm32F745的过程中发现printf有时候不打印信息，单独调试确定了串口初始化和重定向正确，但是在系统整体调试的时候虽然正确运行了却没有打印，通过使用本文所记录的方法暂时解决，但并不确定是否是最正确的解决方案，记录一下以供参考

内容结构如下：

1. 问题现象及最终解决方法

一.问题现象及最终解决方法

现象如简介所述，确认初始化正确，重定向正确，资源分配正确，解决方法如下，在初始化时加入这行代码

setvbuf(stdout, NULL, _IONBF, 0);

表示无缓冲输出，但会增加系统调用的次数

下面贴出串口的初始化代码，应该没有错误

void hal_debug_usart_init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {
0
};
RCC_PeriphCLKInitTypeDef RCC_PeriphClkInit;
// debug串口3时钟源配置
RCC_PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART3;
RCC_PeriphClkInit.Usart1ClockSelection = RCC_USART3CLKSOURCE_SYSCLK;
HAL_RCCEx_PeriphCLKConfig(&RCC_PeriphClkInit);
// 使能串口3时钟
DEBUG_USART_CLK_ENABLE();
// 使能串口3引脚时钟---GPIOC
DEBUG_USART_RX_GPIO_CLK_ENABLE();
DEBUG_USART_TX_GPIO_CLK_ENABLE();
// 串口3收发引脚配置
GPIO_InitStruct.Pin = DEBUG_USART_TX_PIN | DEBUG_USART_RX_PIN;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF7_USART3;
HAL_GPIO_Init(DEBUG_USART_PORT, &GPIO_InitStruct);
// 配置串口3模式
huart3.Instance = USART3;
huart3.Init.BaudRate = 115200;
huart3.Init.WordLength = UART_WORDLENGTH_8B;
huart3.Init.StopBits = UART_STOPBITS_1;
huart3.Init.Parity = UART_PARITY_NONE;
huart3.Init.Mode = UART_MODE_TX_RX;
huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart3.Init.OverSampling = UART_OVERSAMPLING_16;
huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
HAL_UART_Init(&huart3);
HAL_NVIC_SetPriority(USART3_IRQn, 9, 0);
HAL_NVIC_EnableIRQ(USART3_IRQn);
}
void hal_debug_usart_dma_init(void)
{
DEBUG_USART_DMA_CLK_ENABLE();
/* DMA interrupt init */
/* 串口3---DMA1-STREAM1接收 */
HAL_NVIC_SetPriority(DMA1_Stream1_IRQn, 10, 0);
HAL_NVIC_EnableIRQ(DMA1_Stream1_IRQn);
/* 串口3---DMA1-STREAM3发送 */
HAL_NVIC_SetPriority(DMA1_Stream3_IRQn, 10, 0);
HAL_NVIC_EnableIRQ(DMA1_Stream3_IRQn);
hdma_usart3_rx.Instance = DMA1_Stream1;
hdma_usart3_rx.Init.Channel = DMA_CHANNEL_4;
hdma_usart3_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_usart3_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_usart3_rx.Init.MemInc = DMA_MINC_ENABLE;
hdma_usart3_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_usart3_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_usart3_rx.Init.Mode = DMA_NORMAL;
hdma_usart3_rx.Init.Priority = DMA_PRIORITY_HIGH;
hdma_usart3_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
HAL_DMA_DeInit(&hdma_usart3_rx);
HAL_DMA_Init(&hdma_usart3_rx);
__HAL_LINKDMA(&huart3, hdmarx, hdma_usart3_rx);
hdma_usart3_tx.Instance = DMA1_Stream3;
hdma_usart3_tx.Init.Channel = DMA_CHANNEL_4;
hdma_usart3_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_usart3_tx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_usart3_tx.Init.MemInc = DMA_MINC_ENABLE;
hdma_usart3_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_usart3_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_usart3_tx.Init.Mode = DMA_NORMAL;
hdma_usart3_tx.Init.Priority = DMA_PRIORITY_LOW;
hdma_usart3_tx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
HAL_DMA_DeInit(&hdma_usart3_tx);
HAL_DMA_Init(&hdma_usart3_tx);
__HAL_LINKDMA(&huart3, hdmatx, hdma_usart3_tx);
}
int fputc(int ch, FILE *f)
{
/* 发送一个字节数据到串口DEBUG_USART */
HAL_UART_Transmit(&huart3, (uint8_t *)&ch, 1, HAL_MAX_DELAY);
return (ch);
}