CC3220SF-LAUNCHXL: CC3220SF-LAUNCHXL

Hi Kishore,

To switch the SPI clock speed, you will need to first close and then reopen the SPI interface with the new clock rate. This can be done by changing .bitRate in your SPI open parameters.

Since you mentioned that the CS signal must not be de-asserted during the switch, the simplest way to ensure that is to make the CS signal a SW controlled GPIO. To do so, set the SPI peripheral into 3 wire mode, with SW controlled CS. The SPI CS settings are done in CC3200SF_LAUNCHXL.c, in the spiCC3220SDMAHWAttrs struct. Please use the following settings:

    {
        .baseAddr = GSPI_BASE,
        .intNum = INT_GSPI,
        .intPriority = (~0),
        .spiPRCM = PRCM_GSPI,
        .csControl = SPI_SW_CTRL_CS,
        .csPolarity = SPI_CS_ACTIVELOW,
        .pinMode = SPI_3PIN_MODE,
        .turboMode = SPI_TURBO_OFF,
        .scratchBufPtr = &spiCC3220SDMAscratchBuf[CC3220SF_LAUNCHXL_SPI1],
        .defaultTxBufValue = 0,
        .rxChannelIndex = UDMA_CH6_GSPI_RX,
        .txChannelIndex = UDMA_CH7_GSPI_TX,
        .minDmaTransferSize = 10,
        .mosiPin = SPICC32XXDMA_PIN_07_MOSI,
        .misoPin = SPICC32XXDMA_PIN_06_MISO,
        .clkPin = SPICC32XXDMA_PIN_05_CLK,
        .csPin = SPICC32XXDMA_PIN_NO_CONFIG
    }

Then, configure a GPIO in the gpioPinConfigs struct of the same file. If you wanted to keep CS on pin8, then configure GPIO17 as an output. With that, you can use a GPIO_write() to assert CS when needed in your code.

Let me know if you need more clarification or have further questions on this topic.

Regards,

Michael