配置STM32 DMA寄存器时，我无法访问它

Question

我目前使用标准外围设备库在STM32 F407 ZGT6芯片上编写一个驱动程序，使内存能够进行USART6_TX DMA传输。然而，我尝试了很长一段时间，但初始化一直失败：DMA_GetCmdStatus总是返回DISABLE。通过使用GDB，我发现在DMA_Init尝试将配置写入DMA寄存器后，DMACR寄存器保持为0。DMA初始化代码和执行如下：

void DMA_USART6_Init(char* DMA_Start_Pos, uint32_t DMA_Buffer_Size){
DMA_Buffer_Size_GV = DMA_Buffer_Size;
DMA_Start_Pos_GV = DMA_Start_Pos;
/*RCC config*/
RCC_AHB1PeriphResetCmd(RCC_AHB1Periph_DMA2, ENABLE);
/*DMA init*/
//DMA_DeInit(DMA2_Stream7);
DMA_Cmd(DMA2_Stream7, DISABLE);
while ((DMA_GetCmdStatus(DMA2_Stream7) == ENABLE)){}
DMA_StructInit(&DMA_InitStruct);
DMA_InitStruct.DMA_Channel = DMA_Channel_5;
DMA_InitStruct.DMA_PeripheralBaseAddr = USART6_BASE + 0x04;//(uint32_t)&USART6->DR;
DMA_InitStruct.DMA_Memory0BaseAddr = (uint32_t) dubuff;//(uint32_t) DMA_Start_Pos;
DMA_InitStruct.DMA_DIR = DMA_DIR_MemoryToPeripheral;
DMA_InitStruct.DMA_BufferSize = (uint16_t)sizeof(dubuff);//DMA_Buffer_Size;
printf("buffer size should be %d rn", (uint16_t)sizeof(dubuff));
DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStruct.DMA_Mode = DMA_Mode_Circular;
DMA_InitStruct.DMA_Priority = DMA_Priority_High;
DMA_InitStruct.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_Init(DMA2_Stream7, &DMA_InitStruct);
printf("data counter after init %d rn", DMA_GetCurrDataCounter(DMA2_Stream7));
}

对于ENABLE代码

void DMA_USART6_Enable_DMA(char* DMA_Start_Pos, uint32_t DMA_Buffer_Size, int MB){
Max_Buffer = MB;
USART6_init_for_DMA();
DMA_USART6_Init(DMA_Start_Pos, DMA_Buffer_Size);
DMA_USART6_NVIC_Init();
DMA_ITConfig(DMA2_Stream7, DMA_IT_TC, ENABLE);
DMA_Cmd(DMA2_Stream7, ENABLE);
while ((DMA_GetCmdStatus(DMA2_Stream7) == DISABLE)){}//program stucked in this loop
}

对于USART6代码：

void USART6_init_for_DMA(void){
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART6, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_USART6);
GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_USART6);
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);
USART_InitStructure.USART_BaudRate = 57600;//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_Rx | USART_Mode_Tx;
USART_Init(USART6, &USART_InitStructure);
USART_Cmd(USART6, ENABLE);
USART_DMACmd(USART6, USART_DMAReq_Tx, ENABLE);
}

GDB结果：

应该写入DMA CR寄存器的值

图片中的文本1:

367   DMAy_Streamx->CR = tmpreg;
(gdb) print tmpreg 
$7 = 167904576

DMA CR寄存器保持0

图片中的文本2:

371   tmpreg = DMAy_Streamx->FCR;
(gdb) print *DMAy_Streamx
$10 = {CR = 0, NDTR = 0, PAR = 0, M0AR = 0, M1AR = 0, FCR = 0}

请告诉我，如果我能提供任何关于我的问题或我可以进一步尝试的事情。。。注意：在同一个程序中，我的USART6和GPIO运行良好。

Answer 1

当所需的流被激活时，相关寄存器将无法再进行配置。只有在双缓冲模式下，才能根据位CT功能更新存储器地址0和1。您必须先停用相关频道，然后应用更改。

Answer 2

我是OP。一开始，我觉得这可能是一个明显的错误，这是真的。事实证明，我应该使用RCC_AHB1PeriphClockCmd而不是RCC_AHB1 PeriphResetCmd，因为很明显，后来访问的RSTR(RCC重置寄存器(而不是ENR，因此时钟没有启用(大约Codo是正确的(。

好吧，希望看到这个问题的人不要再犯这个尴尬的错误；(