stm32f4 DMA挂起后并不总是启动

Question

所以这个问题是这个问题的 "sequel"：Stm32f4: DMA + ADC Transfer pausing。

同样，我正在尝试实现这样的算法：

在一个通道上以三重交错模式使用 ADC 初始化 DMA
等待外部中断
暂停 DMA 传输和 ADC
在中断中通过USART从内存发送缓冲数据
恢复 DMA 和 ADC
退出中断，转到2。

DMA 和 ADC 挂起和恢复，但有时（在大约 16% 的中断调用中）恢复失败 - DMA 只是从 ADC 写入第一个测量值并停止直到下一个中断，在该中断中 DMA 和 ADC 重新启动（因为它们被暂停并再次恢复）并且 - 好吧，一切 returns 恢复正常，直到下一个这样的错误。

我试过像参考手册所说的那样暂停 DMA：

In order to restart from the point where the transfer was stopped, the software has to read the DMA_SxNDTR register after disabling the stream by writing the EN bit in DMA_SxCR register (and then checking that it is at ‘0’) to know the number of data items already collected. Then:
– The peripheral and/or memory addresses have to be updated in order to adjust the address pointers
– The SxNDTR register has to be updated with the remaining number of data items to be transferred (the value read when the stream was disabled)
– The stream may then be re-enabled to restart the transfer from the point it was stopped

唯一的实际区别在于恢复 DMA 工作时写入的 NDTR 值。在我的例子中它是 buffer_size，在 RefMan 的例子中 - 它是暂停 DMA 时读取的值。在 RefMan 的情况下，DMA 在暂停后不会再次启动。就我而言，正如我上面所说，它开始了，但并非总是如此。

如何防止这种情况发生？

当前的中断代码如下所示：

void EXTI4_IRQHandler(void) {
    uint16_t temp = DMA_GetFlagStatus(DMA2_Stream0, DMA_FLAG_TEIF0);
    if(EXTI_GetITStatus(EXTI_Line4) != RESET) {
        uint16_t fPoint1 = 0;
        uint16_t fPoint2 = 0;

        //Some delay using the TIM2
        TIM_SetCounter(TIM2, 0);
        TIM_Cmd(TIM2, ENABLE);

        //Measure the first point NDTR
        fPoint1 = DMA2_Stream0->NDTR;
        while(TIM_GetITStatus(TIM2, TIM_IT_Update) != SET) {};

        //Measure the second point here.
        fPoint2 = DMA2_Stream0->NDTR;

        if(fPoint1 == fPoint2) {
            //The NDTR does not change!
            //If it does not change, it is stuck at buffer_size - 1
        }

        //Disable the timer
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
        TIM_Cmd(TIM2, DISABLE);

        DMA_Cmd(DMA2_Stream0, DISABLE);
        //Wait until the DMA will turn off
        while((DMA2_Stream0->CR & (uint32_t)DMA_SxCR_EN) != 0x00) {};

        //Turn off all ADCs
        ADC_Cmd(ADC1, DISABLE);
        ADC_Cmd(ADC2, DISABLE);
        ADC_Cmd(ADC3, DISABLE);

        //Send all the data here

        //Turn everything back on

        //Turn the DMA ON again
        DMA_SetCurrDataCounter(DMA2_Stream0, BUFFERSIZE);
        DMA_Cmd(DMA2_Stream0, ENABLE);
        while((DMA2_Stream0->CR & (uint32_t)DMA_SxCR_EN) == 0x00) {};

        //See note @ RefMan (Rev. 12), p. 410
        ADC->CCR &= ~((uint32_t)(0x000000FF));
        ADC->CCR |= ADC_TripleMode_Interl;

        ADC_Cmd(ADC1, ENABLE);
        ADC_Cmd(ADC2, ENABLE);
        ADC_Cmd(ADC3, ENABLE);
        while((ADC1->CR2 & (uint32_t)ADC_CR2_ADON) == 0) {};
        while((ADC2->CR2 & (uint32_t)ADC_CR2_ADON) == 0) {};
        while((ADC3->CR2 & (uint32_t)ADC_CR2_ADON) == 0) {};

        ADC_SoftwareStartConv(ADC1);
    }

    EXTI_ClearITPendingBit(EXTI_Line4);
}

Answer 1

我自己找到了解决方案。我以为是 DMA 问题；然而，这不是ADC的问题。 ADCx->CR 寄存器中的 OVR 标志总是在传输 "stuck" 时设置。因此，我在 ADC 溢出情况下添加了一个中断，并在其中重新启动了 DMA 和 ADC。现在问题已经解决了。

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