Posted on August 02, 2017 at 15:12
Here's some code. Please let me know if more details are needed, but I think the below should be sufficient. DMA setup code followed by my interrupt handlers.
Sean
DMA setup:
#define UART6_RX_DMA_ALL_FLAGS (DMA_FLAG_FEIF1 | DMA_FLAG_DMEIF1 | \
DMA_FLAG_TEIF1 | DMA_FLAG_HTIF1 | DMA_FLAG_TCIF1 )
// USART RX DMA Channel
ConfigDMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART6->DR;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_Channel = DMA_Channel_5;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)RxBuffer;
DMA_InitStructure.DMA_BufferSize = RX_BUFFER_SIZE;
DMA_Cmd(DMA2_Stream1, DISABLE);
DMA_Init(DMA2_Stream1, &DMA_InitStructure);�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
// Enable Rx DMA
DMA_ITConfig(DMA2_Stream1, DMA_IT_TC, ENABLE);
DMA_ClearFlag(DMA2_Stream1, UART6_RX_DMA_ALL_FLAGS);
USART_DMACmd(USART6, USART_DMAReq_Rx, ENABLE);
DMA_Cmd(DMA2_Stream1, ENABLE);�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
Interrupt processing:
// Global to store the count of the data in the buffer
static volatile uint32_t rxBufferContentsSize = 0;
// RxBuffer for DMA
#define RX_BUFFER_SIZE 64
static uint8_t RxBuffer[RX_BUFFER_SIZE];
void __attribute__((used)) USART6_IRQHandler(void)
{
// Only have USART_IT_IDLE enabled
if (USART_GetITStatus(UARTSLK_TYPE, USART_IT_IDLE) == SET)
{
// Disable the DMA - this ought to trigger the TC interrupt
DMA_Cmd(UARTSLK_RX_DMA_STREAM, DISABLE);
// Block on the EN bit to wait for the DMA to be disabled
// (Yes, I plan to do a timeout here here eventually)
while((UARTSLK_RX_DMA_STREAM->CR & CCR_ENABLE_SET) != 0);
// Record the number of bytes the DMA has read out at the time of IDLE
// Is this the appropriate way to determine bytes read? Could be related
// to my underrun errors if the DMA isn't actually finished reading data
// to memory before I disable it, right?
rxBufferContentsSize = RX_BUFFER_SIZE - UARTSLK_RX_DMA_STREAM->NDTR;
// This step is necessary to clear the IDLE interrupt
USART_ReceiveData(UARTSLK_TYPE);
// Would it be a good practice to disable the UART peripheral here as well,
// until the DMA is re-enabled??? Perhaps this is related to the extra byte
// of received data I often see, described by problem number 1 in my post?
}
}
// DMA Rx handler
void __attribute__((used)) DMA2_Stream1_IRQHandler(void)
{
// DMA Rx handler has been entered. This should only happen when the IDLE
// interrupt has been processed, so the data from 0 through rxBufferContentSize
// is supposed to contain one complete, valid packet.
// This is my test function that quickly runs through the buffer starting
// from index 0 through rxBufferContentsSize (see the UART ISR for where that's set)
// In my actual application, this is where the upstream code would be signaled that
// data is ready. This would not be a long, blocking call - we need to get the DMA
// enabled again ASAP to be ready for the next message.
if(!isValidPacket())
{
DEBUG_PRINT('RECEIVED INVALID PACKET');
}
// Clear the Rx Buffer on each iteration so it's easier to inspect for errors
// Won't need to do this in product code.
memset(RxBuffer, 0, RX_BUFFER_SIZE);
// Restart the DMA
// I suppose this is where JW has suggested I do an additional read of the UART first
// Would it be better to have disabled the UART perihperal and only re-enable it when
// I am ready to enable DMA again?
DMA_ClearFlag(DMA2_Stream1, UART6_RX_DMA_ALL_FLAGS);
DMA2_Stream1->NDTR = RX_BUFFER_SIZE;
DMA2_Stream1->M0AR = (uint32_t)RxBuffer;
/* Enable DMA USART TX Stream */
DMA_Cmd(DMA2_Stream1, ENABLE);
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