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TMS320F28054: SPI MOSI output

Martin Kohout
Prodigy 50 points

Part Number: TMS320F28054

Hello,

I'm going to use TMS320F28054 SPI MOSI output to create simple waveform (a pulse or series of pulse) instead of typical SPI communication. Because I do not have HW ready yet I need help to answer following questions.

Assumption is that SPI will be configured as master with desired baud rate to create requested waveform.

Can I configure GPIO Mux to output just SPI MOSI output while SPI MISO and SCLK will not be used at device package pins?

Will last SPI output bit be also last SPI MOSI output pin state until next SPI data will be send out? I mean when I send out SPI data with last bit equal 0 will SPI MOSI be kept low until next SPI transaction? When I send out SPI data with last bit equal 1 will SPI MOSI be kept high until next SPI transaction? 

Have SPI MOSI defined output state after SPI transaction has finished?

Thanks,

Martin

  • 0
    Guru 30330 points

    Martin, 

    1. Yes, There is no problem with only configuring SPISIMO and not bringing out SPICLK and SPISOMI.
    2. The last bit will be held on the line until the next SPI transaction.
    3. See #2

    I hope this help, would you mind sharing what you are trying to do? It is an interesting usage, and I know that we have emulated a deltasigma ADC for some debug purposes. This sounds like a similar situation.

    Thanks,
    Mark

  • 0 in reply to Mark Labbato
    Guru 30330 points
    Martin,

    Did I answer your question sufficiently?

    -Mark
  • 0 in reply to Mark Labbato
    Prodigy 50 points

    Hi Mark,

    thank you very much. Yes, your answer is very good. I just forgot to reply.

    Regarding your previous question about SPI usage. I'm going to use SPI to generate waveform for another device for testing purpose. Nothing interesting.

    But I'm going to use also SPI to communicate over 1-Wire bus by Dallas semiconductor. SPI MISO and MOSI together with external transistor and pull-up will be used to generate and sample 1-Wire signal. With this approach I can use SPI module to do all timing for me on 1-Wire bus.

  • 0 in reply to Martin Kohout
    Guru 30330 points
    Martin,
    Glad to hear that it helped. When you complete you project, be sure to share your final results if you can. It sounds like an interesting project and I'm sure that others would be very interested in how you accomplished it.

    -Mark