beginSPITransmission()

void beginSPITransmission(unsigned short chip_select, bool polarity = false);

void setup() {
    beginSPI(13, 12, 11);  // initializes the SPI communication with the clock pin connected to pin
                           // 13, the data in pin connected to pin 12, and the data out pin connected
                           // to pin 11
}

void loop() {
    beginSPITransmission(10, LOW);  // begins an SPI transmission to the follower chip with the chip
                                    // select pin connected to pin 10, and the polarity of the chip
                                    // select line set to LOW
                                    
    writeSPI(42);                   // sends the value 42 to the follower chip
    endSPITransmission(10, LOW);    // ends the SPI transmission
}