DMA SPI

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Hy,
I have a problem with my DMA Controller.
I would use DMA to send Data over SPI. I know I must use the USART as a SPI Master.
My Problem is when I send Data and I watch them on my oscilloscope then I see that one/two Bytes wouldn't send in the middle of the transaction.
Have anyone the same Problem or an idea?

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Some more info might be helpful.

How many bytes are you sending? Is it the same amount every time? Is it the same bytes that don't show up or different ones? Where is the data originating for the DMA transfer?

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I sending 8 Bytes.
Often the third Byte is missing, but sometimes it is the fourth Byte.
At the beginning I initialise my Data and the DMA Controller.

 uint8_t Data0[NUM_BYTES]={0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88};
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I have found my failure.
I have made a start Trasfer after i enable the Channel.
But by the USART the Transfer starts without any Start Transfer command.

Thank you for your help