TM4C123GH6PM: SoftSSI mapping to SPI lines

Hello Bob,

I think the API to configure SS signal best explains your options - you can either set it and have the Soft SSI driver handle the SS line for you, or manually control SS in your application, whichever works better for you.

//*****************************************************************************
//
//! Sets the GPIO pin to be used as the SoftSSI Fss signal.
//!
//! \param psSSI specifies the SoftSSI data structure.
//! \param ui32Base is the base address of the GPIO module.
//! \param ui8Pin is the bit-packed representation of the pin to use.
//!
//! This function sets the GPIO pin that is used for the SoftSSI Fss signal.
//! If there is not a GPIO pin allocated for Fss, the SoftSSI module does not
//! assert/deassert the Fss signal, leaving it to the application either to do
//! manually or to not do at all if the slave device has Fss tied to ground.
//!
//! The pin is specified using a bit-packed byte, where bit 0 of the byte
//! represents GPIO port pin 0, bit 1 represents GPIO port pin 1, and so on.
//!
//! \return None.
//
//*****************************************************************************
void
SoftSSIFssGPIOSet(tSoftSSI *psSSI, uint32_t ui32Base, uint8_t ui8Pin)
{
    //
    // Save the base address and pin for the Fss signal.
    //
    if(ui32Base == 0)
    {
        psSSI->ui32FssGPIO = 0;
    }
    else
    {
        psSSI->ui32FssGPIO = ui32Base + (ui8Pin << 2);
    }
}

Best Regards,

Ralph Jacobi