#include <msp430.h>
#include "SPI.h"

uchar SPI_CS = 0;

int SPIInit(){

  UCA0CTL1 = UCSWRST;

  // setup A0 for SPI
  UCA0CTL0 = UCMSB | UCMST | (0x10 << 1) | UCSYNC;
  UCA0CTL1 |= UCSSEL_2;
  UCA0BR1 = 0;
  UCA0BR0 = 16; // 1 MHz


  // config port
  //set SEL to USCI (0b01); MOSI (pin 1), MISO (pin 2), CLK (pin 4)
  P1SEL  |= BIT1 | BIT2 | BIT4;
  P1SEL2 |= BIT1 | BIT2 | BIT4;


  UCA0CTL1 &= ~UCSWRST;

  // enable interrupts
  // IE2 |= UCA0TXIE;
  // IFG2 &= ~UCA0TXIFG;

  // set initial values for vars
  SPI_packetC = 0;
  SPI_CS = 0;

  __enable_interrupt();

  return 0;
}

//TODO: add clock freqency configuration
/* 
 * do some configuration before sending the data.
 * 
 * @arg uchar cs: the bit of port 1 connected to the chip select pin of target device
 * @arg enum SPI_Mode: the SPI modus (clock pase and polarity)
 * @arg enum SPI_clock: the clock freqency
 */
void SPIInitSend(uchar cs, enum SPI_Mode mode, enum SPI_Clock clk){
  //TODO: add a clock as powerefficent delay
  while(SPI_CS != 0); // wait for last transmit to be done
      
  // set clock frequency
  UCA0BR0 = clk;

  // set SPI mode
  UCA0CTL0 &= 0x3F; // set mode bits to 0
  UCA0CTL0 |= mode;

  // save chip select
  SPI_CS = cs;
}

//TODO: make it asyncronily with interupt. 
/*
 * Send the packet stored in SPI_packet. it start from SPI_packetC to the last byte
 */
void SPISend(){
  P1OUT &= ~SPI_CS; // select slave

  while(SPI_packetC < 5){
    // send one byte
    UCA0TXBUF = SPI_packet[SPI_packetC];

    //TODO: fix the delay! it's to short with low data speeds
    if(UCA0BR0 > 4) 
      // if de frequency lower than 4 MHz do a manual delay. this is a workaround for the to short delay
      // this works down to 1 MHz
      __delay_cycles(129);
    else
      while(UCB0STAT & UCBUSY); // wait for SPI TX/RX to finish

    // save recieved data
    SPI_packet[SPI_packetC] = UCA0RXBUF;

    // increase counter for next byte
    SPI_packetC++;
  }

  SPI_packetC = 0; // recet counter
  P1OUT |= SPI_CS; // deselect slave
  SPI_CS = 0;
}