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KL25Z custom board with KSDK 2.0: clock registers won't change accordingly

Question asked by Gustavo Leal on Sep 29, 2016
Latest reply on Sep 30, 2016 by Gustavo Leal

On my custom board with MKL25Z128, I'm using KSDK 2.0 with Keil MDK and initializing the clock with the following function to use the internal oscillator (no crystal):

void BOARD_BootClockRUN(void) {

    const sim_clock_config_t simConfig = {
        .pllFllSel = 0U,        /* PLLFLLSEL select FLL. */
        .er32kSrc = 3U,         /* ERCLK32K selection, use LPO. */
        .clkdiv1 = 0x00000000U, /* SIM_CLKDIV1. */


    CLOCK_SetInternalRefClkConfig(kMCG_IrclkEnable, kMCG_IrcFast, 0);

While debugging, I see that the CLOCK_SetSimSafeDivs() function correctly alters the SIM_CLKDIV1 register.

However, when CLOCK_BootToFeiMode executes, the registers won't change to the specified parameters. As an example, the DRST_DRS bit in MCG_C4 should be set to 1, but the function doesn't modify it and it still keeps the value 2.


Also, in the CLOCK_SetInternalRefClkConfig function, the MCG_C1 bit CLKS is not set to 1 to select the internal reference clock, but keeps the value 2, which selects the external reference clock.


My application sets a LPTMR interrupt using the LPO (1kHz) clock, but when I set, e.g., a 1 second interrupt, it triggers every 1.2 seconds.


I tried setting the same clock configuration (internal clock, 41.94MHz) and creating the LPTMR interrupt using Processor Expert and KDS and it works correctly, so I thought it might be something related to KSDK.


Any clues?