HAL_UART_Receive_DMA only receive last byte

[alyssa]

Hi, i want use usart DMA to receive data, but i only get last data by HAL_UART_Receive_DMA.

STM32U575VITX

STM32CUBEMX 6.8.0

STM32CubeIDE 1.12.0

the transmit data is $$......##

my code is in main function

when i use HAL_UART_Receive(), i can get correct data, but it has packet loss to some extend.

when i use HAL_UART_Receive_DMA(), i only get last byte # .

cubemx setting for DMA:

cubemx setting for usart :

usart.c file is attached below.

i try this solution https://community.st.com/t5/stm32-mcus-embedded-software/stm32h750-dma-hal-uart-receive-dma-acting-oddly/m-p/569897 but, still can't solve it.

it will be very helpful, if any one tell me something.

thank you.

[Tesla DeLorean]

The function returns immediately, you can't have multiple operations in flight concurrently. Manage fill of buffer in the completion callback.

Avoid using auto/local buffers for DMA, they have collapsing scope on the stack.

[alyssa]

Hi, let me make the situation more clear.

i can run into IQRHander.

i use the callback function, length=__HAL_DMA_GET_COUNTER can change.  (i think MCU have known the interrupt received by usart, but dont know where to read the buffer data)

observation:

1. hdmarx state is HAL_DMA_STATE_BUSY, HAL_UART_Receive_DMA state is HAL_OK 

2. pRxBuffPtr is #000....... (only first byte have data, other bytes are all 0)

3. hdmarx->init are all 0, if i set HAL_DMA_Init() in usart.c, it will into HardFault_Handler()

4. i change baud rate from 921600 to 115200, but still not work

i attach the .ioc and main.c file below.

 thank you

[embedko · Accepted solution]

Hi. Problem with DMA configuration. You must set Enabled for Destination Address Increment After Transfer.

[Tesla DeLorean]

It's not a clarity issue, its a one that lacks understanding of the mechanics

I've told you HAL_UART_Receive_DMA(&hlpuart1,data,256); returns immediately, not after you have 256 bytes, immediately.

You need some volatile semaphone coming back from the callback indicating it completed and is read for a second usage.

volatile int global_flag = 0;
...
while(1)
{
  if (global_flag == 0) // nothing pending
  {
    global_flag = 1; // busy
    HAL_UART_Receive_DMA(&hlpuart1,data,256);
  }
}

In full completion callback
    global_flag = 0;

[alyssa]

Yes! thank you ,you are right!

After I set this, everything go done well.

[alyssa]

I try this but fail. Still thanks for your helping.

My solution is given.