My board has four SPI ports with common mosi, miso, and sck pins. CS pins are 9, 10, 15, and 24. I can use either the builtin microSD reader or an external reader connected to one of the SPI ports.
The code to initialize the SD card:
// SPI
#define PIN_SPI_CS_10 10
#define PIN_SPI_CS_9 9...