/*FUNCTION**********************************************************************
*
* Function Name : SPI_HAL_SetBaud
* This function takes in the desired bitsPerSec (baud rate) and calculates the nearest
* possible baud rate without exceeding the desired baud rate unless the baud rate requested is
* less than the absolute minimum in which case the minimum baud rate will be returned. The returned
* baud rate is in bits-per-second. It requires that the caller also provide the frequency of the
* module source clock (in Hertz).
*
*END**************************************************************************/
uint32_t SPI_HAL_SetBaud(SPI_Type * base, uint32_t bitsPerSec, uint32_t sourceClockInHz)
{
uint32_t prescaler, bestPrescaler;
uint32_t rateDivisor, bestDivisor;
uint32_t rateDivisorValue;
uint32_t realBaudrate, bestBaudrate;
uint32_t diff, min_diff;
uint32_t baudrate = bitsPerSec;
/* find combination of prescaler and scaler resulting in baudrate closest to the
* requested value
*/
min_diff = 0xFFFFFFFFU;
/* Set the maximum divisor bit settings for each of the following divisors */
bestPrescaler = 7;
bestDivisor = 8;
/* Set baud rate to minimum baud rate possible, adjust prescale divisor and divisor
* bit settings in acutal divisor values
*/
bestBaudrate = sourceClockInHz / ((bestPrescaler + 1) * (bestDivisor * 64));
/* In all for loops, if min_diff = 0, the exit for loop*/
for (prescaler = 0; (prescaler <= 7) && min_diff; prescaler++)
{
rateDivisorValue = 2U; /* Initialize to div-by-2 */
for (rateDivisor = 0; (rateDivisor <= 8U) && min_diff; rateDivisor++)
{
/* calculate actual baud rate, note need to add 1 to prescaler */
realBaudrate = ((sourceClockInHz) /
((prescaler + 1) * rateDivisorValue));
/* calculate the baud rate difference based on the conditional statement*/
/* that states that the calculated baud rate must not exceed the desired baud rate*/
if (baudrate >= realBaudrate)
{
diff = baudrate-realBaudrate;
if (min_diff > diff)
{
/* a better match found */
min_diff = diff;
bestPrescaler = prescaler; /* Prescale divisor SPIx_BR register bit setting */
bestDivisor = rateDivisor; /* baud rate divisor SPIx_BR register bit setting */
bestBaudrate = realBaudrate;
}
}
/* Multiply by 2 for each iteration, possible divisor values: 2, 4, 8, 16, ... 512 */
rateDivisorValue *= 2U;
}
}
/* write the best prescalar and baud rate scalar */
SPI_WR_BR(base, SPI_BR_SPR(bestDivisor) | SPI_BR_SPPR(bestPrescaler));
/* return the actual calculated baud rate*/
return bestBaudrate;
}
/*FUNCTION**********************************************************************
*
* Function Name : SPI_HAL_Init
* Description : RestoreS SPI to reset configuration.
* This function basically resets all of the SPI registers to their default setting including
* disabling the module.
*
*END**************************************************************************/
void SPI_HAL_Init(SPI_Type * base)
{
SPI_WR_C1(base, SPI_C1_CPHA_MASK);
SPI_WR_C2(base, 0);
SPI_WR_BR(base, 0);
#if FSL_FEATURE_SPI_16BIT_TRANSFERS
SPI_WR_MH(base, 0);
SPI_WR_ML(base, 0);
#else
SPI_WR_M(base, 0);
#endif
}
// See fsl_spi_hal.h for documentation of this function.
void spi_hal_reset(SPI_Type * baseAddr)
{
// Restore those control and configuration registers which are used to
// be operated
SPI_WR_C1(baseAddr, SPI_C1_CPHA_MASK);
SPI_WR_C2(baseAddr, 0);
SPI_WR_BR(baseAddr, 0);
#if FSL_FEATURE_SPI_16BIT_TRANSFERS
SPI_WR_ML(baseAddr, 0);
#else // FSL_FEATURE_SPI_16BIT_TRANSFERS
SPI_WR_M(baseAddr, 0);
#endif // FSL_FEATURE_SPI_16BIT_TRANSFERS
}
