Function LEUART_BaudrateSet

bsp/efm32/Libraries/emlib/src/em_leuart.c:254–322

/ * @brief * Configure baudrate (or as close as possible to specified baudrate). * * @note * The setting of a baudrate requires synchronization into the * low frequency domain. If the same register is modified before a previous * update has completed, this function will stall until the previous * synchronization has completed. * * @param[in] leuart * Pointer to LEUART periphe

 *   Baudrate to try to achieve for LEUART.
 ******************************************************************************/
void LEUART_BaudrateSet(LEUART_TypeDef *leuart,
                        uint32_t refFreq,
                        uint32_t baudrate)
{
  uint32_t          clkdiv;
  CMU_Clock_TypeDef clock;

  /* Inhibit divide by 0 */
  EFM_ASSERT(baudrate);

  /*
   * We want to use integer division to avoid forcing in float division
   * utils, and yet keep rounding effect errors to a minimum.
   *
   * CLKDIV in asynchronous mode is given by:
   *
   * CLKDIV = 256*(fLEUARTn/br - 1) = ((256*fLEUARTn)/br) - 256
   *
   * Normally, with fLEUARTn appr 32768Hz, there is no problem with overflow
   * if using 32 bit arithmetic. However, since fLEUARTn may be derived from
   * HFCORECLK as well, we must consider overflow when using integer arithmetic.
   *
   * The basic problem with integer division in the above formula is that
   * the dividend (256 * fLEUARTn) may become higher than max 32 bit
   * integer. Yet, we want to evaluate dividend first before dividing in
   * order to get as small rounding effects as possible. We do not want
   * to make too harsh restrictions on max fLEUARTn value either.
   *
   * Since the last 3 bits of CLKDIV are don't care, we can base our
   * integer arithmetic on the below formula
   *
   * CLKDIV/8 = ((32*fLEUARTn)/br) - 32
   *
   * and calculate 1/8 of CLKDIV first. This allows for fLEUARTn
   * up to 128MHz without overflowing a 32 bit value!
   */

  /* Get current frequency? */
  if (!refFreq)
  {
    if (leuart == LEUART0)
    {
      clock = cmuClock_LEUART0;
    }
#if (LEUART_COUNT > 1)
    else if (leuart == LEUART1)
    {
      clock = cmuClock_LEUART1;
    }
#endif
    else
    {
      EFM_ASSERT(0);
      return;
    }

    refFreq = CMU_ClockFreqGet(clock);
  }