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STM32L4 Reading SPI with Receive or TransmitReceive returns different values

Question asked by Alex Wagner on May 22, 2018

Hey guys,

i am using a custom board with a STM32L452CE MCU. I am trying to implement a 2 Line SPI with a sensor as slave. Communicating via Transmit and Receive separately works fine. However if I want to switch to TransmitReceive there are wrong values returned. I monitor the SPI with a Logic Analyzer.

 

Send byte:                                         0xD0

Returned byte:                                  0x60

Received byte by TransmitReceive: 0x50

 

Right now i tried working with DMA, but it doesn't change anything. With or without DMA i get the same wrong readings with TransmitReceive and Correct readings with Transmit and Receive only.

 

I attached some screenshots of the problem.

 

Thank you for any hints!

 

Alex

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