freeRTOS + DMA (STM32).

Question:

I understand that the forum is not so specialized, but I will still ask my question here. Probably someone will tell you. There is a simple working program – freeRTOS + diode flashing (there is still a little crap, but not the point), the platform is STM32 (F217). I decided to try adding USART + DMA. Initialization takes place in the following order:

  1. порты GPIO (для диодов);
  2. контроллер NVIC (для лабуды =));

  3. DMA :

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
    
    DMA_DeInit(DMA2_Stream7 );
    DMA_InitTypeDef DMA_InitStructure;
    DMA_InitStructure.DMA_Channel = DMA_Channel_4;
    DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_BASE + offsetof(USART_TypeDef, DR);
    DMA_InitStructure.DMA_Memory0BaseAddr = (u32) buffer;
    DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
    DMA_InitStructure.DMA_BufferSize = strlen(buffer);
    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_Circular;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    //DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA2_Stream7, &DMA_InitStructure);`
    
  4. USART:

    USART_InitTypeDef USART_InitStructure;   //для инициализации USART
    
    GPIO_StructInit(&GPIO_InitStructure);
    
    //настроить выводы, к которым подключены RX и TX
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);   //тактирование GPIOA
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;          //линия RX
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN; //вход, третье состояние
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStructure);             //выполнить инициализацию
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;           //линия TX
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;     //макс частота сигнала
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;      //симетричный выход
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);             //выполнить инициализацию
    
    //настройка модуля USART
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    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_Rx | USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStructure);
    
  5. DMA + USART:

    USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
    USART_Cmd(USART1, ENABLE);
    DMA_Cmd(DMA2_Stream7, ENABLE);
    

Actually, if you comment on the DMA initialization, the initial version of the program (flashing with a diode) works as it should. But if you uncomment – the LED stupidly lights up and that's it. Those. the task (but rather the sheduler) hangs.

What could be the reason?

Answer:

It seems to me that you have not configured the pins correctly for yusart.
They must be configured as Alternative Functions.
Also, in this DMA_InitStructure.DMA_PeripheralBaseAddr you can simply put USART1->DR and that's it:

DMA_InitStructure.DMA_PeripheralBaseAddr = USART1->DR;

Please tell me if it worked …
Why aren't you using MXCube? Of course, the approach with HAL is a little different, but it works more stable than SPL …

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