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STM32F3 UART with DMA transmit max. 4 bytes

Question asked by moennicke.bernd on Jan 2, 2015
Latest reply on Feb 6, 2015 by Montassar BEN ROMDHANE

I've test the STM32F303 for using it in a new project. The configuration and libbrary are used from the CubeMX with the IAR compiler.
Now I can maximum transmit 4 bytes over the UART with one DMA transfer.

Here my configuration for the DMA and UART:
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 57600;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONEBIT_SAMPLING_DISABLED ;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;

    hdma_usart2_rx.Instance = DMA1_Channel6;
    hdma_usart2_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
    hdma_usart2_rx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_usart2_rx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_usart2_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
    hdma_usart2_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
    hdma_usart2_rx.Init.Mode = DMA_NORMAL;
    hdma_usart2_rx.Init.Priority = DMA_PRIORITY_LOW;


    hdma_usart2_tx.Instance = DMA1_Channel7;
    hdma_usart2_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
    hdma_usart2_tx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_usart2_tx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_usart2_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
    hdma_usart2_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
    hdma_usart2_tx.Init.Mode = DMA_NORMAL;
    hdma_usart2_tx.Init.Priority = DMA_PRIORITY_LOW;


I start the transmission with the function HAL_UART_Transmit_DMA (&huart2, pData, uSize);
When I call this function with uSize 1,2,3 or 4 works all fine. All values bigger than 4 have the same result as 4.
Have somebody a idea?