Function DAC_PrescaleCalc

bsp/efm32/Libraries/emlib/src/em_dac.c:240–266

/ * @brief * Calculate prescaler value used to determine DAC clock. * * @details * The DAC clock is given by: HFPERCLK / (prescale ^ 2). * * @param[in] dacFreq DAC frequency wanted. The frequency will automatically * be adjusted to be below max allowed DAC clock. * * @param[in] hfperFreq Frequency in Hz of reference HFPER clock. Set to 0 to * use currently defined HFPER clock set

 *   <= @p dacFreq.
 ******************************************************************************/
uint8_t DAC_PrescaleCalc(uint32_t dacFreq, uint32_t hfperFreq)
{
  uint32_t ret;

  /* Make sure selected DAC clock is below max value */
  if (dacFreq > DAC_MAX_CLOCK)
  {
    dacFreq = DAC_MAX_CLOCK;
  }

  /* Use current HFPER frequency? */
  if (!hfperFreq)
  {
    hfperFreq = CMU_ClockFreqGet(cmuClock_HFPER);
  }

  /* Iterate in order to determine best prescale value. Only a few possible */
  /* values. We start with lowest prescaler value in order to get first */
  /* equal or below wanted DAC frequency value. */
  for (ret = 0; ret <= (_DAC_CTRL_PRESC_MASK >> _DAC_CTRL_PRESC_SHIFT); ret++)
  {
    if ((hfperFreq >> ret) <= dacFreq)
      break;
  }

  return((uint8_t)ret);
}


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