In the file app_sdcard.c of the SDK13.0.0, an assert is done when calling app_sdc_init() with a pin P0.0. Can i safely use P0.0 with the assert deactivated or should i use another pin ?
ASSERT(p_config->cs_pin && p_config->miso_pin
&& p_config->mosi_pin && p_config->sck_pin);
On the nRF52840 Preview DK board, P0.00 and P0.01 are by default used for the 32.768 kHz crystal and are not available as GPIO on the connectors. If P0.00 and P0.01 are needed as normal I/Os, the 32.768 kHz crystal can be disconnected and the GPIO routed to the connectors, by shorting some solder-bridges on the PDK. For the low-frequency clock (LFCLK), using an external 32 kHz crystal as source will give lower average current consumption than using the internal RC oscillator. I would therefore recommend using some other pins for the SD card.
I'm using a proprietary PCB that already has the connection on the SD card with P0.0. So it's too late for changing that. I will try to use the PCA10056 with those pin to see if it's work.
Ok, in that case you can just ignore/remove the assert().