#include <nrf.h>

// count to us (micro seconds) conversion factor
// set in start_timer()
static volatile float countToUs = 1;

// counter
static volatile uint32_t tCount = 0;


#ifdef __cplusplus
extern "C" {
#endif

// Timer 1 IRQ handler
// just increment count
void TIMER1_IRQHandler(void)
{
    if (NRF_TIMER1->EVENTS_COMPARE[1] &&
            NRF_TIMER1->INTENSET & TIMER_INTENSET_COMPARE1_Msk) {

        // clear compare register event
        NRF_TIMER1->EVENTS_COMPARE[1] = 0;

        // increment count
        tCount++;

        Serial.println("Entered 3");
    }
}

#ifdef __cplusplus
}
#endif

// set up and start Timer1
void start_timer(void)
{
    NRF_TIMER1->MODE = TIMER_MODE_MODE_Timer;
    NRF_TIMER1->TASKS_CLEAR = 1;
    // set prescalar n
    // f = 16 MHz / 2^(n)
    uint8_t prescaler = 0;
    NRF_TIMER1->PRESCALER = prescaler;
    NRF_TIMER1->BITMODE = TIMER_BITMODE_BITMODE_16Bit;

    // 16 MHz clock generates timer tick every 1/(16000000) s = 62.5 nano s
    // With compare enabled, the interrupt is fired every: 62.5 * comp1 nano s
    // = 0.0625*comp1 micro seconds
    // multiply this by 2^(prescalar)

    uint16_t comp1 = 500;
    // set compare
    NRF_TIMER1->CC[1] = comp1;

    // set conversion factor
    countToUs = 0.0625 * comp1 * (1 << prescaler);

    //printf("timer tick = %f us\n", countToUs);

    // enable compare 1
    NRF_TIMER1->INTENSET =
        (TIMER_INTENSET_COMPARE1_Enabled << TIMER_INTENSET_COMPARE1_Pos);

    // use the shorts register to clear compare 1
    NRF_TIMER1->SHORTS = (TIMER_SHORTS_COMPARE1_CLEAR_Enabled <<
                          TIMER_SHORTS_COMPARE1_CLEAR_Pos);

    // enable IRQ
    NVIC_EnableIRQ(TIMER1_IRQn);

    Serial.println("Entered 2");

    // start timer
    NRF_TIMER1->TASKS_START = 1;

}

void setup()
{
    // put your setup code here, to run once:
    Serial.begin(9600);

    delay(2000);

    start_timer();
}

void loop()
{
    // put your main code here, to run repeatedly:
    Serial.println("Entered 1");
    __WFE();
}