#include <msp430g2553.h>
#include "spi.h"


void __attribute__ ((interrupt (USCIAB0RX_VECTOR))) receive() {
  if (UC0IFG & UCB0RXIFG) {
    // receive an octet
  }
}


void spiInit() {
  // SPI slave
  // BIT4: UCB0STE
  // BIT5: UCB0CLK
  // BIT6: UCB0SOMI
  // BIT7: UCB0SIMO
  P1SEL |= BIT4 | BIT5 | BIT6 | BIT7;
  P1SEL2 |= BIT4 | BIT5 | BIT6 | BIT7;

  // most significant bit first, enable STE
  UCB0CTL0 = UCSYNC | UCMSB | UCMODE_2;
  UCB0CTL1 = 0x00;

  // enable RX interrupt
  UC0IE |= UCB0RXIE;
}