Is it possible to use P0.00 and P0.01 for I2C? I'm using RTC for LFCLK, so I thought these would be available as GPIO.

[James H]

I've designed a custom board for the NRF52832. Current consumption is not a major concern, and the pin location was convenient, so I wanted to use P0.00 and P0.01 for I2C. I've set the LFCLK to the RTC, and so I thought it would be OK to use those pins. My application gets hung up though when trying to use them. Setting I2C to use different pins resolves that issue, but would require a board redesign. Can I use P0.00 and .01 for I2C? Is some other configuration necessary?

[hmolesworth]

Worth checking the settings, have a look at this code:

    // 32kHz Osc pins can be used as GPIOs or 32kHz Oscillator, special case
    if ( (PinId == RCC_OSC_OUT_PIN) && (NRF_CLOCK->LFCLKSRC & 0x000001) ) return "RTC-OSC-OUT";
    if ( (PinId == RCC_OSC_IN_PIN)  && (NRF_CLOCK->LFCLKSRC & 0x000001) ) return "RTC-OSC-IN";

Typically the pins are set to RTC mode by functions invoked by this:

    // Configure RTC
    lfclk_config();

__STATIC_INLINE void nrf_clock_lf_src_set(nrf_clock_lfclk_t source)
{
    NRF_CLOCK->LFCLKSRC =
        (uint32_t)((source << CLOCK_LFCLKSRC_SRC_Pos) & CLOCK_LFCLKSRC_SRC_Msk);
}

[Nguyen Hoan Hoang]

Those pins are for the 32KHz crystal of the RTC but default.  If you want to use those pins as gpio, you need to remap them and use internal RC for your timer.

[James H]

I have set the LFCLK to use the internal oscillator, but that doesn't seem to be all that is needed.

[hmolesworth]

Did you try the code I posted above? This is (typically) the default code, pins used for crystal not io; how are you setting LFCLK?

// <o> CLOCK_CONFIG_LF_SRC  - LF Clock Source

// <0=> RC
// <1=> XTAL
// <2=> Synth

#ifndef CLOCK_CONFIG_LF_SRC
#define CLOCK_CONFIG_LF_SRC 1
#endif

nrf_clock_lf_src_set((nrf_clock_lfclk_t)CLOCK_CONFIG_LF_SRC);

The board .h default (for PCA10040 for example):

// Low frequency clock source to be used by the SoftDevice
#define NRF_CLOCK_LFCLKSRC      {.source        = NRF_CLOCK_LF_SRC_XTAL,            \
                                 .rc_ctiv       = 0,                                \
                                 .rc_temp_ctiv  = 0,                                \
                                 .accuracy     = NRF_CLOCK_LF_ACCURACY_20_PPM}

[hmolesworth]

Similar post I responded to here