Selecting HFCLK as clock source for hardware timer when using Zephyr

Question

Hello,

To get the highest precision, I would like to use nRF's hardware timers instead of Zephyr's timers.
To do so, I access nRF's timers configuration as follow:

timer_init(void)
{
    IRQ_CONNECT(TIMER1_IRQn, 0, hc_meas_timer_handler, NULL, 0);
    NRF_TIMER1->BITMODE = 32;
    NRF_TIMER1->PRESCALER = 8;
    NRF_TIMER1->MODE = TIMER_MODE_MODE_Timer;
    NRF_TIMER1->CC[0] = 1250;
    NRF_TIMER1->SHORTS = 0;
    NRF_TIMER1->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos;
    NRF_TIMER1->INTENSET = TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos;
    NRF_TIMER1->TASKS_START = 1;
}

Even if it seems to work, I'm still wondering if there is a way to ensure that this timer use external HFCLK as clock source at it is the more precise ?

Thank you,
Regards

Vidar Berg · Accepted Answer

Hello, 
 The TIMERs will run of the internal oscillator unless the application has requested the High-frequency (32 MHz) crystal oscillator (HFXO) . The internal oscillator as a worst case tolerance of -+8%. 
 Here is an example on how you can use the On-Off manager to request the crystal oscillator: https://github.com/nrfconnect/sdk-nrf/blob/85fef3ca6680d73aa1e68169cb0d45f859a43f3c/samples/peripheral/radio_test/src/main.c#L11 
 Regards, 
 Vidar

Selecting HFCLK as clock source for hardware timer when using Zephyr

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