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microcontroller in SPI Slave mode when clock is continous and no SSEL

Discussion in 'Embedded' started by blisca, Nov 14, 2012.

  1. blisca

    blisca Guest

    Please can i have your help?

    I'm confused about the following situation:

    A transceiver is connected in SPI mode to a microcontroller(LPC12xx).
    The transceiver outputs a continous clock ,and it does not drive any SSEL
    line to enable the SPI section of the microcontroller.
    The microcontroller should decide when to start a data transmission,but just
    enabling its SPI module it goes in Busy condition and i have found no way to
    change it.
    Polling the BSY flag goes to a never ending loop,just as the uC is still
    sending out something,or receiving and it is always busy.

    How is the right way to deal with similar situations?

    Many thanks for help or hints or links
    Diego
     
    blisca, Nov 14, 2012
    #1
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  2. blisca

    Rob Gaddi Guest

    If your transceiver outputs a continuous clock, and has no SSEL, then
    how does it expect the receiving device to frame the data?
     
    Rob Gaddi, Nov 14, 2012
    #2
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  3. blisca

    blisca Guest

    Thanks for your answer
    Mine is..I dont'know...
    the transceiver is
    http://www.analog.com/static/imported-files/data_sheets/ADF7021-N.pdf
    if you take a look at page 46 Figure 60 you can see how microcontroller and
    transceiver are connecter.None of lower output signals SWD or SREAD acts as
    SSEL.

    At least i could use those signals to write into control registers,to enable
    TX mode only when i need it,but i don't think that i could have a known
    number of clock pulses in this way.

    Thanks for your attention
    Diego
     
    blisca, Nov 14, 2012
    #3
  4. blisca

    hamilton Guest

    You mean this figure 60, the one that states:
    Figure 60. ADF7021-N (UART Mode) to Asynchronous Microcontroller Interface

    This is NOT using the SPI interface for this mode of operation.

    The paragraph heading should have told you something: UART Mode

    Please re-read these paragraphs and form your question from there.

    Its figure 61 that uses SPI.

    hamilton
     
    hamilton, Nov 14, 2012
    #4
  5. blisca

    blisca Guest

    Thank you ,
    i realized that the datasheet in my PC is not the same as the one that i
    linked.
    Is Figure 61.
     
    blisca, Nov 15, 2012
    #5
  6. blisca

    Tauno Voipio Guest


    To your original question:

    The payload interface (TxRxCLK and TxRxDATA) transfers just a raw bit
    stream with no framing provided, see figures 8 and 9 in the linked
    data sheet. It is up to you to decode the bit porridge. A suggested
    framing is in figure 54 of the data sheet. The raw bit stream is not
    very well suited to a SPI interface, though it is so named by AD.

    You might be better off using the UART mode with an UART interface
    on the host processor.
     
    Tauno Voipio, Nov 15, 2012
    #6
  7. blisca

    blisca Guest

    Thank you too,Tauno
    i did something working on SPI,but i 'm not able to master it completely,
    by now i'm on a trivial software handling of that communication,using a GPIO
    edge interrupt
    and a pulse clock counter and it works correctly.
    UART mode is not allowed for the modulation that was decided by the RF pals

    Thanks again to you all
     
    blisca, Nov 15, 2012
    #7
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