STM32F407通过复位按键触发外部中断，用DMA方式从串口1发一个100字节的信息，按一次发一次

您可以使用STM32F407的外部中断和DMA功能来实现此操作。首先，您需要配置外部中断以便在按下复位按键时触发。然后，您需要配置串口1以使用DMA发送100字节的信息。最后，您需要编写代码以便在外部中断触发时启动DMA传输。以下是可能的代码示例：

// 外部中断配置
void EXTI_Config(void)
{
    EXTI_InitTypeDef EXTI_InitStructure;

    // 使能GPIO时钟
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    // 配置GPIO为输入模式
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // 配置外部中断线
    EXTI_InitStructure.EXTI_Line = EXTI_Line0;
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);

    // 配置中断优先级
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
}

// 串口1 DMA发送配置
void USART1_DMA_Config(void)
{
    // 使能DMA时钟
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);

    // 配置DMA通道
    DMA_InitTypeDef DMA_InitStructure;
    DMA_InitStructure.DMA_Channel = DMA_Channel_4;
    DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
    DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)message;
    DMA_InitStructure.DMA_BufferSize = 100;
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART1->DR;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
    DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
    DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
    DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
    DMA_Init(DMA2_Stream7, &DMA_InitStructure);

    // 配置USART1
    USART_InitTypeDef USART_InitStructure;
    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_Tx;
    USART_Init(USART1, &USART_InitStructure);

    // 使能USART1
    USART_Cmd(USART1, ENABLE);

    // 配置DMA中断
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream7_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    // 使能DMA传输完成中断
    DMA_ITConfig(DMA2_Stream7, DMA_IT_TC, ENABLE);
}

// 外部中断处理函数
void EXTI0_IRQHandler(void)
{
    // 清除中断标志
    EXTI_ClearITPendingBit(EXTI_Line0);

    // 启动DMA传输
    DMA_Cmd(DMA2_Stream7, ENABLE);
}

// DMA传输完成中断处理函数
void DMA2_Stream7_IRQHandler(void)
{
    // 清除中断标志
    DMA_ClearITPendingBit(DMA2_Stream7, DMA_IT_TC);

    // 关闭DMA传输
    DMA_Cmd(DMA2_Stream7, DISABLE);
}

请注意，此代码示例仅用于演示目的，可能需要进行适当修改才能在您的应用程序中正常工作。