stm32 UART-DMA one character transfer problem

[mdg82]

Posted on June 01, 2015 at 14:21

Hello! I'm using STM32F407 processor. When I'm trying to send 1 byte via USART-DMA (for example 0x72) I get two bytes ''72 72'' in terminal.If I send two or more bytes everything is okay. If I send something from terminal I can't receive one byte, only two or more bytes can be received. Maybe someone can help to solve this problem. Thanks.

[qwer.asdf]

Posted on June 01, 2015 at 14:43

Not without seeing your code. What library are you using?

[Tesla DeLorean]

Posted on June 01, 2015 at 15:48

Aren't there more efficient ways to send one character? Seems like DMA would add a lot of overhead in this case.

[mdg82]

Posted on June 02, 2015 at 09:25

Here's the function that sends buffer

uint32_t USART_Send(USART_Handle* handle, uint8_t *data, uint32_t size) {     assert_param(handle);     assert_param(handle->instance);     assert_param(data);     assert_param(size <= sizeof(handle->buffer_tx));          if(handle->buffer_tx_busy)         return 0;     handle->buffer_tx_busy = 1;          memcpy(handle->buffer_tx, data, size);          /* Configure DMA Stream source address */   handle->dma_tx_instance->M0AR = (uint32_t)handle->buffer_tx;     /* Configure DMA Stream data length */     handle->dma_tx_instance->NDTR = size;          LEDS_ON_GREEN(handle->params.led);          DMA_Cmd(handle->dma_tx_instance, ENABLE);     if(!_DMA_Cmd(handle->dma_tx_instance, ENABLE) && handle->buffer_tx_busy)     {         Errors.Error_uart = ERROR_FAIL_UART_DMA_CMD;         return 0;     }          return size; }