SPI_DMA Slave Receive only after reset

[egywell]

Posted on June 15, 2018 at 07:53

Hi st

I try to recieve spi dma slave by stm32f746 as slave 

i send two bytes for test from master raspberry 

when reset mcu it receive ok  when i repeat request it receive nothing and rx buffer not changed

i tried checking over run and interrupts and error found nothing 

it seem to be time sync problem with master but how it work after reset then stop working without any error

[T J]

Posted on June 15, 2018 at 11:54

there is no time sync, the input clock bits are counted to 8 then the data is latched.

I guess you are clearing the Rx buffer

// initialise by clearing residual bytes in DR

    while ((hspi1.Instance->SR  & SPI_FLAG_RXNE))

        RxSPI = hspi1.Instance->DR;

// wait for next Rx

while ((hspi1.Instance->SR  & SPI_FLAG_RXNE)) ;

RxSPI = hspi1.Instance->DR;  // have new byte  //should save to buffer

otherwise you may have a poor ground between your SPI device and the F746.

can you check the clock line is going to ground on a scope connected to the F746 ground.?

[egywell]

Posted on June 15, 2018 at 13:49

Thanks for replyI tried clean buffer same problemNo problem with groundWhen I use spi polling no DMA it is OK which mean there something with timing I do not know

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Re: SPI_DMA Slave Receive only after reset

reply from T J in STM32 MCUs Forum - View the full discussion

there is no time sync, the input clock bits are counted to 8 then the data is latched.

I guess you are clearing the Rx buffer

// initialise by clearing residual bytes in DR

while ((hspi1.Instance->SR & SPI_FLAG_RXNE))

RxSPI = hspi1.Instance->DR;

// wait for next Rx

while ((hspi1.Instance->SR & SPI_FLAG_RXNE)) ;

RxSPI = hspi1.Instance->DR; // have new byte //should save to buffer

otherwise you may have a poor ground between your SPI device and the F7

can you check the clock line is going to ground on a scope connected to the F746 ground.?

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