Solved
When reading USART, DMA instantaneously completes
Posted on May 15, 2018 at 13:48
Please see code below.
I'm trying to read from USART using DMA.
Please see the last line DMA1_Channel3->CCR |= DMA_CCR_EN;
When I step over that line,
CNDTR instantaneously resets to zero like it has finished reading, also destination buffer is populated by multiple instances of the same char that was in USART1->RDR.It looks like DMA believes that the same char is constantly arriving into RDR and available for transfer.
I don't expect any actual USART transmission at that time.
What am I doing wrong please?
void ScheduleUsartDmaRead(){
USART1->CR1 &= ~USART_CR1_TE; USART1->CR1 |= USART_CR1_RE; USART1->CR1 |= USART_CR1_UE; // enable usart DMA1_Channel3->CCR &= ~DMA_CCR_EN; // disable DMA to set registers DMA1_Channel3->CCR &= ~DMA_CCR_DIR; // peripheral to memory DMA1->IFCR = DMA_FLAG_GL3; // clear flags DMA1_Channel3->CNDTR = usartBufferSize; // set buffer size DMA1_Channel3->CPAR = (uint32_t)(&(USART1->RDR)); // USART register address DMA1_Channel3->CMAR = (uint32_t)(usartInBuffer); // memory address DMA1_Channel3->CCR |= DMA_CCR_EN; // start DMA}