accel.c

int accel_spi_init() 
{
  if (bcm2835_init() != 1)
  {
    perror("Could not initialize BCM2835 library");
    return -1;
  }

  // enable SPI for accelerometer
  bcm2835_spi_begin();
  bcm2835_spi_setDataMode(BCM2835_SPI_MODE0);
  bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_128);
  bcm2835_spi_chipSelect(BCM2835_SPI_CS0);
  bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW);
  return 0;
}

// other functions here to read/write accelerometer

power.c

int power_spi_init()
{
  if (bcm2835_init() != 1)
  {
    perror("Could not initialize BCM2835 library");
    return -1;
  }

  // enable SPI for accelerometer
  bcm2835_spi_begin();
  bcm2835_spi_setDataMode(BCM2835_SPI_MODE1);
  bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_8192);
  bcm2835_spi_chipSelect(BCM2835_SPI_CS1);
  bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS1, HIGH);
  return 0;
}

// other functions here to read/write power management