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Error_Code
Associate II
January 17, 2024
Solved

SPI COMMUNICATION THREE WIRE/ FOUR WIRE

  • January 17, 2024
  • 1 reply
  • 13013 views

Hi,

I have doubt with the spi communication setup in this configuration. I'm using two sensors where one of the sensor only support 3 wire spi and another  is 4 wire .I have a single spi in mcu. The hardware setup is followed by mapping four wire spi to mcu(mcu is configured in full duplex mode) and put a resistor between miso and mosi and given to three wire spi slave. 

>Is it possible to make proper communication in this setup?

>If this is okay how the master mcu will differentiate betweeen them?

    Best answer by TDK

    Technically, yes. You would need to reconfigure the peripheral in 3-wire mode when you wanted to use that mode and switch to 4-wire mode for the other sensors. Not something that will be supported by CubeMX.

    1 reply

    Ghofrane GSOURI
    Ghofrane GSOURI
    ST Technical Moderator
    January 17, 2024

    Hello @Error_Code 

    First let me thank you for posting.

    1- Yes you can make a proper communication using this setup.
    Serial Peripheral Interface (SPI) allows full-duplex or half-duplex synchronous serial communication with multiple devices over 3 or 4 wires.
    For example  by checking the datasheet of the sensor ADXL345 ( Digital Accelerometer)

    GhofraneGSOURI_0-1705485628712.png

     


    2- To differentiate between the two sensors, you can use a separate GPIO pin as an additional chip select (CS) for the 3 wire sensor.

    Thx

    Ghofrane

     

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    E
    Error_CodeAuthor
    Associate II
    January 17, 2024

    Thanks for your response,

    Is it possible to use both three wire and 4 wire spi in same spi bus? if yes how it will work?

     

    TDK
    TDKBest answer
    January 17, 2024

    Technically, yes. You would need to reconfigure the peripheral in 3-wire mode when you wanted to use that mode and switch to 4-wire mode for the other sensors. Not something that will be supported by CubeMX.

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