driver_pit.c

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/*! \file driver_pit.c
    \brief Provides a simple abstraction for a periodic interval timer.

   Bare metal implementations of the sensor fusion library require at least
   one periodic interrupt for use as a timebase for sensor fusion functions.
   The Periodic Interval Timer (PIT) is one such module that is commonly
   found on NXP Kinetis MCUs.  The PIT functions are only referenced at the
   main() level.  There is no interaction within the fusion routines themselves.
*/

#include "board.h"
#include "fsl_pit.h"
#include "pin_mux.h"
#include "clock_config.h"

/*******************************************************************************
 * Definitions
 ******************************************************************************/
#define PIT_LED_HANDLER     PIT0_IRQHandler
#define PIT_IRQ_ID          PIT0_IRQn
#define PIT_SOURCE_CLOCK    CLOCK_GetFreq(kCLOCK_BusClk)

volatile bool   pitIsrFlag = false;

void PIT_LED_HANDLER(void)
{
    /* Clear interrupt flag.*/
    PIT_ClearStatusFlags(PIT, kPIT_Chnl_0, PIT_TFLG_TIF_MASK);
    pitIsrFlag = true;
}

void pit_init(uint32_t microseconds)
{
    /* initialize PIT */
    pit_config_t    pitConfig;                  // Declare KSDK PIT configuration structure
    PIT_GetDefaultConfig(&pitConfig);           // Fill out that structure with defaults
    PIT_Init(PIT, &pitConfig);                  // PIT is declared by the KSDK
    // We choose to use Channel 0 of the PIT.  That can obviously be changed
    PIT_SetTimerPeriod(PIT, kPIT_Chnl_0, USEC_TO_COUNT(microseconds, PIT_SOURCE_CLOCK));
    PIT_EnableInterrupts(PIT, kPIT_Chnl_0, kPIT_TimerInterruptEnable);
    EnableIRQ(PIT_IRQ_ID);
    PIT_StartTimer(PIT, kPIT_Chnl_0);
}