RE: Understanding SPIM3 Hardware CS without SDK

Einar Thorsrud — Thu, 05 May 2022 11:23:28 GMT

Hi,

There are tre registers that are relevant for CSN on SPIM3. The simplest way to get an overview of how this works is to refer to the SPIM chapter in the PS, and see how CSN. is configured in the nrfx driver. That essentially just call this function (copy-pasted from nrf_spim.h):

__STATIC_INLINE void nrf_spim_csn_configure(NRF_SPIM_Type *    p_reg,
                                            uint32_t           pin,
                                            nrf_spim_csn_pol_t polarity,
                                            uint32_t           duration)
{
    p_reg->PSEL.CSN = pin;
    p_reg->CSNPOL = polarity;
    p_reg->IFTIMING.CSNDUR = duration;
}

(As a side note, I would generally advice against avoiding drivers unless you have a good reason for doing so, for a few of reasons: They will save you time, they will make your code more readable, and they often contain errata workarounds that it is easy to miss.)