实现了使用3个打印缓冲组连续打印的功能，如果3个缓冲组全满了就在前一个组打印完成后打印：printf buffer is full！剩下的2个缓冲组继续打印。

初步实现了该功能，显示效果如下：

DMA1 transmission successful!successful,successful,successful
print buffer is full!

DMA2 transmission successful!successful,successful,successful

DMA3 transmission successful!successful,successful,successful

DMA1 transmission successful!successful,successful,successful
print buffer is full!

DMA2 transmission successful!successful,successful,successful

DMA3 transmission successful!successful,successful,successful

DMA1 transmission successful!successful,successful,successful
print buffer is full!

DMA2 transmission successful!successful,successful,successful

DMA3 transmission successful!successful,successful,successful

DMA1 transmission successful!successful,successful,successful
print buffer is full!

DMA2 transmission successful!successful,successful,successful

DMA3 transmission successful!successful,successful,successful

宏：

#define UART_BUFFLEN 256

#define PRINTFBUF_NUM 3

#define PRINTFULL ("print buffer is full!\r\n")

typedef enum
{
    BUFF_EMPTY = 0,
    BUFF_HAS_DATA,
    BUFF_FULL
}BUFF_FLAG;
typedef struct
{
    u16 sPriority;
    u16 sLength ;
    BUFF_FLAG iFullFlag;
    u8 ucBuffer[UART_BUFFLEN];
}ST_UARTBUFFER;

函数：

中断：

/*******************************************************************************
* Function Name  : DMA1_Channel4_IRQHandler
* Description    : This function handles DMA1 Channel 4 interrupt request.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void DMA1_Channel4_IRQHandler(void)
{
    u8 ucIndex;
    ST_UARTBUFFER *pUart1SendBuffer;
    volatile ST_PRINTFBUFFER *pPrintfBuffer;

   
    if(DMA_GetITStatus(DMA1_IT_TC4))
    {
        DMA_ClearITPendingBit(DMA1_IT_TC4);
        pUart1SendBuffer = GetUART1SendBufferAddr();
        pPrintfBuffer = GetPrintfBufferAddr ();
        (pUart1SendBuffer + pPrintfBuffer->ucIndex)->iFullFlag = BUFF_EMPTY;
        if (pPrintfBuffer->iFullFlag == BUFF_FULL)
        {
            DMAUART1_Configuration(PRINTFULL,strlen(PRINTFULL));
           
            pPrintfBuffer->iFullFlag = BUFF_HAS_DATA;
        }
        else
        {
            for (ucIndex = 0 ; ucIndex < PRINTFBUF_NUM ;ucIndex++)
            {
                if ( (pUart1SendBuffer + ucIndex)->iFullFlag== BUFF_FULL)
                {
                    pPrintfBuffer->ucIndex = ucIndex;
                    DMAUART1_Configuration((pUart1SendBuffer + pPrintfBuffer->ucIndex)->ucBuffer,(pUart1SendBuffer + pPrintfBuffer->ucIndex)->sLength);

                    break;
                }
            }
            if (ucIndex == PRINTFBUF_NUM)
            {
                pPrintfBuffer->iFullFlag == BUFF_EMPTY;
            }
        }
       
       
       
       
    }
    if(DMA_GetITStatus(DMA1_IT_HT4))
    {
        DMA_ClearITPendingBit(DMA1_IT_HT4);

    }
    if(DMA_GetITStatus(DMA1_IT_TE4))
    {
        DMA_ClearITPendingBit(DMA1_IT_TE4);

    }
    if(DMA_GetITStatus(DMA1_IT_GL4))
    {
        DMA_ClearITPendingBit(DMA1_IT_GL4);

    }
}

每次打印的数据长度不能超过UART_BUFFLEN个
int printf(const char *format ,... )
{
    va_list arg;
    int rv;
    u8 ucIndex;
    static u8 ucCounter = 0;
   

    for (ucIndex = 0 ; ucIndex < PRINTFBUF_NUM ;ucIndex++)
    {
        if ( g_acUART1SendBuffer[ucIndex].iFullFlag == BUFF_EMPTY)
        {
            g_acUART1SendBuffer[ucIndex].iFullFlag = BUFF_FULL;
            va_start(arg, format);
            rv = vsprintf(g_acUART1SendBuffer[ucIndex].ucBuffer, format, arg);
            g_acUART1SendBuffer[ucIndex].sLength = rv;
            va_end(arg);
            break;
        }
        else
        {

        }
    }

    if (ucIndex == PRINTFBUF_NUM)
    {
        g_stPrintBuffer.iFullFlag = BUFF_FULL;
        ucCounter ++;
    }
    else
    {
        if (g_stPrintBuffer.iFullFlag != BUFF_FULL)
        {
            for (ucIndex = 0 ; ucIndex < PRINTFBUF_NUM ;ucIndex++)
            {
                if ( g_acUART1SendBuffer[ucIndex].iFullFlag == BUFF_FULL)
                {
                    g_stPrintBuffer.ucIndex = ucIndex;
                    break;
                }
            }
            if (ucIndex == PRINTFBUF_NUM)
            {
                g_stPrintBuffer.iFullFlag = BUFF_FULL;
            }
            else
            {
                DMAUART1_Configuration(g_acUART1SendBuffer[g_stPrintBuffer.ucIndex].ucBuffer,g_acUART1SendBuffer[g_stPrintBuffer.ucIndex].sLength);
                g_stPrintBuffer.iFullFlag = BUFF_HAS_DATA;
            }
           
        }
        else
        {

        }
    }
   
   
    return rv;
}

void DMAUART1_Configuration(u8 *uiSendBuf,u32 uiLength)
{
    DMA_InitTypeDef DMA_InitStructure;
    DMA_DeInit ((DMA_Channel_TypeDef*)DMA1_Channel4_BASE);
    DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40013804;//&(USART1.DR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)uiSendBuf;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = uiLength;
    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_Medium;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel4, &DMA_InitStructure);

     DMA_ITConfig(DMA1_Channel4, DMA_IT_TC, ENABLE);
     DMA_Cmd(DMA1_Channel4, ENABLE);
}
测试方法：

            printf("\r\nDMA1 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA2 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA3 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA4 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA5 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA6 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA7 transmission successful!successful,successful,successful\r\n");
            printf("\r\nDMA8 transmission successful!successful,successful,successful\r\n");
只有3个缓冲组，所以4，5，6，7，8均来不及打印，

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