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SPI on RM48

Vaidyanathan Balakrishnan
Intellectual 705 points
Other Parts Discussed in Thread: RM48L952

We are using the RM48L952 device and have connected a write only peripherial to SPI3. Our connections are:

SIMO  -> peripheral data out

SPICLK -> perihperial clock

CS is controlled separately through another pin programmed as GIO.

We have connected SOMI pin as a GIo for another functionality, not for this peripheral. The issue is that the hardware SPI does not work, while I do pin toggled SPI, it works.

The RM48 reference documentation mentions that for SPI towork "SPISOMI and/or SPISIMO" should be configured for SPI functionality.

Is it and  or or? In our case, can I expect h/w spi to work or do I have to change the SOMI pin connection?

  • 0
    TI__Expert 4610 points

    Hi Vaidyanthan,

    Can you let us know what you have configured the SIMO/SPICLK pins as? As a GIO pin or SPI functional pin? In pin toggled SPI, i am assuming that you would have configured it as a GIO pin. For hardware SPI to work, you will have to configure these pins as SPI functional pin. Please refer to SPI Pin Control Register 0 (SPIPC0) register for configuring these pins.

    As a sanity for the hardware SPI, you have an option to do a digital/analog loopback using SPI test registers to transmit and recieve to make sure the SPI is configured properly, before proceeding with an external peripheral.

    Regards,

    Praveen

  • 0 in reply to Praveen Kumar Ravichandran
    Intellectual 705 points

    Hello Praveen,

    I have configured SIMO for SPI functionality, SPICLK  for spi functionality

    The SOMI pin is configured as a GIO pin, used for controlling another peipheral, not connected to the SPI.

    The datasheet says that for the internal SPI state machine to work properly the "SIMO and/or SOMI pins should be configured for SPI" - my question is whether the SPI working depends only on one of the pins configured for SPI or both pins?

    I already have hardware SPI code working in another application using the RML952.


    Vaidi.

  • 0 in reply to Vaidyanathan Balakrishnan
    TI__Mastermind 22715 points

    Vaidi,

    For proper SPI operation, you have to configure at least SPICLK, SIMO and SOMI pins as SPI function. Transmission and reception happen simultaneously on SPI. I would suggest you to check TRM for SPI operation modes (3-pin, 4-pin, and 5-pin modes).

    Thanks and regards,

    Zhaohong