How to enable the external 32MHZ crystal oscillator through the internal capacitor

[singerW]

I'm using a custom development board and I want to enable timer 0 through the external 32MHZ crystal oscillator. Here is my configuration:

prj.config:
# Enable the UART driver

CONFIG_CLOCK_CONTROL=y

CONFIG_CLOCK_CONTROL_NRF=y

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

CONFIG_SOC_ENABLE_LFXO=n

CONFIG_SOC_HFXO_CAP_INTERNAL=y

CONFIG_SOC_HFXO_CAP_INT_VALUE_X2=24
app.overlay:

&hfxo {

    status = "okay";

    load-capacitors = "internal";

    load-capacitance-femtofarad = <15000>; 

};

&timer0 {

    compatible = "nordic,nrf-timer";

    status = "okay";

    label = "MY_TIMER0";

    interrupts = <15 NRF_DEFAULT_IRQ_PRIORITY>;

    prescaler = <0>;

};

main.c:

void my_hfclk_start(void)

{

    struct onoff_manager *mgr =

        z_nrf_clock_control_get_onoff(CLOCK_CONTROL_NRF_SUBSYS_HF);

    __ASSERT_NO_MSG(mgr != NULL);

    sys_notify_init_callback(&hfclk_cli.notify, hfclk_on_callback);

    int ret = onoff_request(mgr, &hfclk_cli);

    __ASSERT_NO_MSG(ret >= 0);

}

   if (NRF_CLOCK->HFCLKSTAT & CLOCK_HFCLKSTAT_STATE_Msk) {

            if (NRF_CLOCK->HFCLKSRC & CLOCK_HFCLKSRC_SRC_Msk) {

                printk("HFCLK source is HFXO\n");

            } else {

                printk("HFCLK source is HFINT (16 MHz)\n");

            }

        } else {

            printk("HFCLK is not running\n");

        }

        uint32_t prescaler = NRF_TIMER0->PRESCALER;

        printk("TIMER0 PRESCALER: %u\n", prescaler);

        uint32_t freq = counter_get_frequency(counter_dev);

        printk("Counter frequency: %u Hz\n", freq);

The printing result is:
HFCLK source is HFXO
TIMER0 PRESCALER: 0
Counter frequency: 16000000 Hz
I really can't find the cause of the problem, I'm using NCS V3.1.0.

 

[Asbjørn]

Hello Slim,

The clock source available to timer0 is the PCLK1M (Peripheral CLK 1MHz) or PCLK16M https://docs-be.nordicsemi.com/bundle/ps_nrf5340/page/ip/timer/doc/image/block.svg?_LANG=enus

You can't get the 32MHz crystal oscillation to the timer directly. It's only available as the HFCLK source to the peripherals.

Clock setup and names: https://docs.nordicsemi.com/bundle/ps_nrf5340/page/chapters/clock/doc/clock.html

Best regards

Asbjørn

[singerW]

Hello Asbjørn, thank you for your reply
Sorry, I didn't read the manual carefully. Does this mean that although I configured to use HFXO, after being processed by the HFCLK system, the clock source of the timer is still only 16MHZ？

[Asbjørn]

Hello Slim

singerW said:

Does this mean that although I configured to use HFXO, after being processed by the HFCLK system, the clock source of the timer is still only 16MHZ？

Yes, this is correct.

Asbjørn