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sjenyart
sjenyart
Associate II
January 30, 2017
Question

STM32F4: Receiving USART DMA Tx on Rx

  • January 30, 2017
  • 1 reply
  • 596 views
Posted on January 30, 2017 at 20:38

I've configured DMA for Tx and Rx on USART 3 on an STM32F4.  The device on the other end is a Bluetooth module.  I am, for some reason, receiving my transmitted command back as a reception.   Is this expected behavior?

I've confirmed that my commands are properly formed and are being received by the Bluetooth module.  I can see this in its behavior and its responses (which are also coming in via DMA Rx on USART 3). I've confirmed Tx and Rx are not shorted and the module does not appear to be echoing commands back.

Possible I have something misconfigured or some other bug but I thought I would just check whether this rings a bell for anyone.

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    1 reply

    waclawek.jan
    waclawek.jan
    Super User
    January 30, 2017
    Posted on January 30, 2017 at 21:20

    Overlapping buffers? Messed-up setting of DMA pointer registers?

    Hazy crystal ball today.

    JW

    PS.

    >the module does not appear to be echoing commands back

    the easiest way to check is to disconnect the module

    [EDIT] correcting myself: the easiest way to check is not to configure any Rx/Tx pin in GPIO

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