Can the software adjust the internal load capacitance of the nrf5340 crystal oscillator

[Август]

Hello，

Purpose: Adjust 5340 frequency offset.

I want to use software adjust the internal load capacitance, but I don't know how to do it.

I found this below.

Can you give me some advice?

[Kenneth]

Hi,

It looks like this is under discussion on how these values can be controlled. As it is today it they are set in:

See zephyr/soc/arm/nordic_nrf/nrf53/soc.c: nordicsemi_nrf53_init

Though you may also set this in the application by including hal/nrf_oscillators.h and call: 

nrf_oscillators_lfxo_cap_set(NRF_OSCILLATORS, your_cap_value);

Best regards,
Kenneth

[Август]

Thank you Kenneth, but I want to adjust the 32Mhz crystals.

[Kenneth]

You should be able to use the api in hal/nrf_oscillators.h for that also, see api here:

/**
 * @brief Function for configuring the internal capacitors of HXFO.
 *
 * The capacitance of internal capacitors ranges from 7 pF to 20 pF in 0.5 pF steps.
 * To calculate the correct @p cap_value, use the following equation:
 * CAPVALUE = (1+FICR->XOSC32MTRIM.SLOPE/16) * (CAPACITANCE*2-14) + FICR->XOSC32MTRIM.OFFSET
 *
 * @param[in] p_reg     Pointer to the structure of registers of the peripheral.
 * @param[in] enable    True if internal capacitors are to be enabled, false otherwise.
 * @param[in] cap_value Value representing capacitance, calculated using provided equation.
 *                      Ignored when internal capacitors are disabled.
 */
NRF_STATIC_INLINE void nrf_oscillators_hfxo_cap_set(NRF_OSCILLATORS_Type * p_reg,
                                                    bool                   enable,
                                                    uint32_t               cap_value);

Just call this in the beginning of the application.