//******************************************************************************
//   MSP430xG461x Demo - USCI_B0 I2C Master TX multiple bytes to MSP430 Slave
//
//   Description: This demo connects two MSP430's via the I2C bus. The master
//   transmits to the slave. This is the master code. It continuously
//   transmits an array of data and demonstrates how to implement an I2C
//   master transmitter sending multiple bytes using the USCI_B0 TX interrupt.
//   ACLK = 32kHz, MCLK = SMCLK = TACLK = BRCLK = 1MHz
//
//                                 /|\  /|\
//                MSP430xG461x     10k  10k    MSP430xG461x
//                    slave         |    |        master
//              -----------------   |    |  -----------------
//            -|XIN  P3.1/UCB0SDA|<-|---+->|P3.1/UCB0SDA  XIN|-
//       32kHz |                 |  |      |                 | 32kHz
//            -|XOUT             |  |      |             XOUT|-
//             |     P3.2/UCB0SCL|<-+----->|P3.2/UCB0SCL     |
//             |                 |         |                 |
//
//   Andreas Dannenberg/ M. Mitchell
//   Texas Instruments Inc.
//   October 2006
//   Built with IAR Embedded Workbench Version: 3.41A
//******************************************************************************
#include "msp430xG46x.h"

unsigned char *PTxData;                     // Pointer to TX data
unsigned char TXByteCtr;
const unsigned char TxData[] =              // Table of data to transmit
{
  0x11,
  0x22,
  0x33,
  0x44,
  0x55
};

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
  UCB0CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset
  UCB0BR0 = 11;                             // fSCL = SMCLK/11 = 95.3kHz
  UCB0BR1 = 0;
  UCB0I2CSA = 0x48;                         // Slave Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  IE2 |= UCB0TXIE;                          // Enable TX interrupt

  while (1)
  {
    PTxData = (unsigned char *)TxData;      // TX array start address
    TXByteCtr = sizeof TxData;              // Load TX byte counter
    UCB0CTL1 |= UCTR + UCTXSTT;             // I2C TX, start condition
    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
                                            // Remain in LPM0 until all data
                                            // is TX'd
    while (UCB0CTL1 & UCTXSTP);             // Loop until STP is TX'd
  }
}

//------------------------------------------------------------------------------
// The USCIAB0TX_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count. Also, TXData
// points to the next byte to transmit.
//------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  if (TXByteCtr)                            // Check TX byte counter
  {
    UCB0TXBUF = *PTxData++;                 // Load TX buffer
    TXByteCtr--;                            // Decrement TX byte counter
  }
  else
  {
    UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
    IFG2 &= ~UCB0TXIFG;                     // Clear USCI_B0 TX int flag
    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
  }
}