Is it possible to configure nRF54L15 for SPI without SDI / MISO and use that pin for other functions?

RE: Is it possible to configure nRF54L15 for SPI without SDI / MISO and use that pin for other functions?

AlexZander — Fri, 08 Aug 2025 12:06:41 GMT

We have confirmed using the nRF54L15DK that it is indeed possible to configure SPI without MISO and use the remaining pin as a GPIO. Just require confirmation that we are using `NRF_PSEL_DISCONNECTED` correctly but this does seem to be the case.

RE: Is it possible to configure nRF54L15 for SPI without SDI / MISO and use that pin for other functions?

AlexZander — Tue, 05 Aug 2025 16:29:10 GMT

Hi Susheel.

I understand that NRF_SPI_PIN_NOT_CONNECTED is defined as 0xFFFFFFFF however it is not clear how I would use this from the DTS file.

I did find NRF_PSEL_DISCONNECTED so would appreciate if you would confirm if this is correct please?

&pinctrl {
    spi21_default: spi21_default {
        group1 {
            psels = <NRF_PSEL(SPIM_SCK, 1, 8)>,
                    <NRF_PSEL(SPIM_MOSI, 1, 7)>,
                    <NRF_PSEL_DISCONNECTED(SPIM_MISO)>;
        };
    };
};

RE: Is it possible to configure nRF54L15 for SPI without SDI / MISO and use that pin for other functions?

Susheel Nuguru — Tue, 29 Jul 2025 07:43:12 GMT

Alex,

It looks like you can omit SDI pin assignment to SPIM. In the Nordic HAL you do this by passing the standard NRF_PSEL_DISCONNECTED constant for the MISO pin; under Zephyr you must explicitly set the devicetree’s miso-pin to 0xFFFFFFFF rather than dropping it altogether. Once that’s done, P1.10 (your would-be SDI pin) remains a free GPIO you can configure for your other signal. I have not tried this myself, but it seems very possible to do this.

RE: Is it possible to configure nRF54L15 for SPI without SDI / MISO and use that pin for other functions?

Susheel Nuguru — Fri, 25 Jul 2025 14:16:31 GMT

Alex, Apologies for delays in response, I need to double check the specs to see if you can use the SPI pin on something else. I will try to come back to you with more info early next week.