/*!
* @cond DOXYGEN_PRIVATE
*
* @brief Sets up timer with divider settings closest to the requested period in microseconds.
*
* The function gets the value of the base frequency of the timer via clock manager and calculates required
* divider ratio. If the required period is a large value, then the code will try to use a low-frequency
* external clock if available.
*
* Called by hwtimer_set_freq() and hwtimer_set_period().
* Fills in the divider (actual total divider) and modulo (sub-tick resolution) members of the hwtimer_t structure.
*
* @param hwtimer[in] Pointer to hwtimer structure.
* @param period[in] Required period of timer in micro seconds.
*
* @return kHwtimerSuccess Success.
* @return kHwtimerInvalidInput Divider is equal too big.
*
* @see HWTIMER_SYS_SystickInit
* @see HWTIMER_SYS_SystickDeinit
* @see HWTIMER_SYS_SystickStart
* @see HWTIMER_SYS_SystickStop
* @see HWTIMER_SYS_SystickGet_time
* @see HWTIMER_SYS_SystickIsrAction
*/
static _hwtimer_error_code_t HWTIMER_SYS_SystickSetDiv(hwtimer_t *hwtimer, uint32_t period)
{
assert(NULL != hwtimer);
uint64_t divider;
#if FSL_FEATURE_SYSTICK_HAS_EXT_REF
/* Set the clock source back to core freq */
CLOCK_SYS_SetSystickSrc(kClockSystickSrcCore);
#endif
/* Get Core clock frequency */
hwtimer->clockFreq = CLOCK_SYS_GetSystickFreq();
divider = (((uint64_t)hwtimer->clockFreq * period)) / 1000000U ;
/* if divider is greater than 24b value we return an error */
if ((divider - 1U) & ~SysTick_LOAD_RELOAD_Msk)
{
#if FSL_FEATURE_SYSTICK_HAS_EXT_REF
/* Check if we can use a slower clock source to get required period */
CLOCK_SYS_SetSystickSrc(kClockSystickSrcExtRef);
hwtimer->clockFreq = CLOCK_SYS_GetSystickFreq();
divider = (((uint64_t)hwtimer->clockFreq * period)) / 1000000U ;
if ((divider - 1U) & ~SysTick_LOAD_RELOAD_Msk)
{
return kHwtimerInvalidInput;
}
#else
return kHwtimerInvalidInput;
#endif
}
/*
* A start value of 0 (divider == 1) is possible, but has no effect because the
* SysTick interrupt and COUNTFLAG are activated when counting from 1 to 0.
*/
if (divider == 1U)
{
divider = 2U; /* Set smallest possible value for divider. */
}
SysTick->LOAD = divider - 1U;
/* Store in struct. */
hwtimer->divider = divider;
hwtimer->modulo = divider;
return kHwtimerSuccess;
}
/*
** ===================================================================
** Method : OSA_TimeInit (component fsl_os_abstraction)
**
** Description :
** This function initializes the timer used in BM OSA, the
** functions such as OSA_TimeDelay, OSA_TimeGetMsec, and the
** timeout are all based on this timer.
** This method is internal. It is used by Processor Expert only.
** ===================================================================
*/
void OSA_TimeInit(void)
{
uint64_t divider;
/* Disable timer and interrupt */
SysTick->CTRL = 0U;
/* A write of any value to current value register clears the field to 0, and also clears the SYST_CSR COUNTFLAG bit to 0. */
SysTick->VAL = 0U;
#if FSL_FEATURE_SYSTICK_HAS_EXT_REF
/* Set the clock source back to core freq */
CLOCK_SYS_SetSystickSrc(kClockSystickSrcCore);
#endif
/* Get SysTick counter input frequency and compute divider value */
divider = ((((uint64_t)CLOCK_SYS_GetSystickFreq() * OSA1_TIMER_PERIOD_US)) / 1000000U);
assert(divider != 0U);
/* Set divide input clock of systick timer */
SysTick->LOAD = (uint32_t)(divider - 1U);
/* Set interrupt priority and enable interrupt */
NVIC_SetPriority(SysTick_IRQn, 7U);
/* Run timer and enable interrupt */
SysTick->CTRL = (SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk | SysTick_CTRL_TICKINT_Msk);
}
