Problems on RX data on stm32f091 using uart and dma

[Denis Gottardello]

Hi. After many hours my stm32f091 board does not receive what I send to it using uart.

Please could someone confirm that I'm using uart, rx and dma correctly?

So this is my sequence:

CubeMX -> usart1 -> DMA Settings -> add

(on RX, circular, memory)

Usart1 global interrupt: checked

main.c

/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
 
bool ReadyRead0= false;
std::vector<unsigned char> VBufferSerial0Read;
unsigned char MicroBufferSerial0Read[2];
unsigned long LastByteIn0;
 
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart) {
	if (huart->Instance== USART1) {
		VBufferSerial0Read.push_back(MicroBufferSerial0Read[0]);
		LastByteIn0= HAL_GetTick();
		ReadyRead0= true;
	}
}
 
/* USER CODE END PFP */
 
int main(void)
{
	HAL_UART_Receive_DMA(&huart1, (uint8_t*)&MicroBufferSerial0Read, 1);
    for(;;) {
        if (ReadyRead0) {
            ......
            ......
            ......
            ReadyRead0= false;
        }
    }
}

[randy2]

There should be an example in your device firmware package. You are not checking what the HAL returns. whats happening in your debug...

[in mozbek we trust]

Yes you should as @randy2​ says you should check what happening in your debug

[Denis Gottardello]

Is my code ok? Is there a better way to use dma on rx channel, without to know how many bytes are coming?

[randy2]

Hi there,

Yes you can use IDLE interrupts in normal mode, not circular. The was a good example of code if you google "Efficiently receive UART data using DMA"

[T J]

Excellent work, Tick, Tick Tick....

my sequence:
 
CubeMX -> usart1 -> DMA Settings -> add
(on RX, circular, memory)
Usart1 global interrupt: checked

this is the Polling method..

In your process, are you waiting for a byte or a length ?

either way, you can Peek inside the RxDMAbuffer without reading it..

that is, if you are waiting for a length or sequence set.. You can Peek without touching

Usually a buffer has PtrIN and PtrOUT

on startup

PtrIN =0; // not needed

PtrOUT =0; // needed

if PtrIN - PtrOUT =0, there is no data in the buffer...

If the DMA receives a byte, PtrIN is calculated from the DMAbufferPointer.

U1RxBufferPtrIN =  U1RxBufSize - huart2.hdmarx->Instance->CNDTR;

used here to check the UNread length of the buffer

char readableU1(void) {
    U1RxBufferPtrIN =  U1RxBufSize - huart2.hdmarx->Instance->CNDTR;
    return U1RxBufferPtrIN - U1RxBufferPtrOUT;  //UNread length
}

I had to initialise the Rx interrupt, but I dont use the callback.

char readU1(void) {
    char readByte = Usart1RxDMABuffer[U1RxBufferPtrOUT++];
    if (U1RxBufferPtrOUT >= U1RxBufSize) U1RxBufferPtrOUT = 0;
    return readByte;
}

[Denis Gottardello]

Your approach is very interesting.

I have just applied it and started to test.

I hope my demo board will work correctly till monday.

Have a nice weekend.