MKW30Z HW RTC without external 32KHz quartz oscillator

[lucianfiran]

KW40Z_Connectivity_Software_1.0.1 (KSDK_1.3.0) IAR 7.50

Is it possible to use hardware RTC without external crystal oscillator ?

If the chip runs in DCDC bypass mode same question.

[jorge_a_vazquez]

Hi Lucian Firan

Yes, you can use LPO, witch is a clock generated by the PMC. This change is made when you call CLOCK_SetBootConfig(&g_defaultClockConfigRun);

defaultClockConfigRun is a structure defined as:

const clock_manager_user_config_t g_defaultClockConfigRun =
{
    .mcgConfig =
    {
        .mcg_mode           = kMcgModeBLPE, // Work in BLPE mode.
        .irclkEnable        = true,  // MCGIRCLK enable.
        .irclkEnableInStop  = false, // MCGIRCLK disable in STOP mode.
        .ircs               = kMcgIrcSlow, // Select IRC32k.
        .fcrdiv             = 0U,    // FCRDIV is 0.

        .frdiv   = 5U,
        .drs     = kMcgDcoRangeSelLow,  // Low frequency range
        .dmx32   = kMcgDmx32Default,    // DCO has a default range of 25%
        .oscsel  = kMcgOscselOsc,       // Select 
    },
    .simConfig =
    {
        .pllFllSel = kClockPllFllSelFll,    // PLLFLLSEL select FLL.
        .er32kSrc  = kClockEr32kSrcOsc0,     // ERCLK32K selection, use OSC0.
        .outdiv1   = 0U,
        .outdiv4   = 1U,
      
    }
};‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

So, you need to change .er32kSrc from kClockEr32kSrcOsc0 to kClockEr32kSrcLpo.

Hope this information helps you
Have a great day,
Jorge Alcala

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