Failing to receive data from UART in DMA mode

0
votes

I am trying to receive 8 bytes from my pc on my NUCLEO F446RE stm32 board. Transmitting to the pc works. The problem is, I am unable to receive data using DMA. I saw an example with almost the same code and it has worked for the person. If I use the interrupt mode (just change HAL_UART_Receive_DMA to HAL_UART_Receive_IT, it does work and the RX Complete callback is being called.

Here is the complete main.c. DMA is in circular mode.

main.c

https://pastebin.com/1W4BCjxB

2
stm32stm32f4nucleocubemxstm32cubeide
Somehow, this code does work: github.com/MYaqoobEmbedded/STM32-Tutorials/blob/master/… – Knee Caps

2 Answers

2
votes

I got it solved, it is actually ridiculous.

So, this is part of the code that CubeMX generates:

MX_GPIO_Init();
MX_USART2_UART_Init();
MX_DMA_Init();

If I order it as follows:

MX_GPIO_Init();
MX_DMA_Init();
MX_USART2_UART_Init();

It works!!!

0
votes

You haven't initialized the DMA variables as well as handler for the DMA interrupt. You will need to do something along these lines

Initialize DMA:

hdma_usart2_rx.Instance = DMA2_Stream1;
hdma_usart2_rx.Init.Channel = DMA_CHANNEL_2;
hdma_usart2_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_usart2_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_usart2_rx.Init.MemInc = DMA_MINC_DISABLE;
hdma_usart2_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_usart2_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_usart2_rx.Init.Mode = DMA_CIRCULAR;
hdma_usart2_rx.Init.Priority = DMA_PRIORITY_HIGH;
hdma_usart2_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
HAL_DMA_Init(&hdma_usart2_rx);

void DMA2_Stream2_IRQHandler(void)
{
    HAL_NVIC_ClearPendingIRQ(DMA2_Stream2_IRQn);
    HAL_DMA_IRQHandler(&hdma_usart1_rx);
}

HAL_UART_Receive_DMA only starts the DMA and does not handle the interrupt and the data transfer.