//******************************************************************************
//    MSP430x47xx Demo - USCI_B0 I2C Master RX multiple bytes from 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
//
//                                 /|\  /|\
//                 MSP430x47xx     10k  10k     MSP430x47xx
//                    slave         |    |        master
//              -----------------   |    |  -----------------
//            -|XIN  P3.1/UCB0SDA|<-|---+->|P3.1/UCB0SDA  XIN|-
//       32kHz |                 |  |      |                 | 32kHz
//            -|XOUT             |  |      |             XOUT|-
//             |     P3.2/UCB0SCL|<-+----->|P3.2/UCB0SCL     |
//             |                 |         |                 |
//
//  P. Thanigai / K.Venkat
//  Texas Instruments Inc.
//  November 2007
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.42A
//******************************************************************************
#include "msp430x47x4.h"

unsigned char *PRxData;                     // Pointer to RX data
unsigned char RXByteCtr;
volatile unsigned char RxBuffer[5];         // Allocate 128 byte of RAM

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P3SEL |= BIT1+BIT2;                       // Assign I2C pins to USCI_B0
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
                                            // 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 |= UCB0RXIE;                          // Enable RX interrupt

  while (1)
  {
    PRxData = (unsigned char *)RxBuffer;    // Start of RX buffer
    RXByteCtr = 5;                          // Load RX byte counter
    UCB0CTL1 |= UCTXSTT;                    // I2C start condition
    __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
                                            // Remain in LPM0 until all data
                                            // is RX'd
    __no_operation();                       // Set breakpoint >>here<< and
  }                                         // read out the RxBuffer buffer
}
//-------------------------------------------------------------------------------
// The USCIB0 data ISR is used to move received data from the I2C slave
// to the MSP430 memory. It is structured such that it can be used to receive
// any 2+ number of bytes by pre-loading RXByteCtr with the byte count.
//-------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  RXByteCtr--;                              // Decrement RX byte counter
  if (RXByteCtr)
  {
    *PRxData++ = UCB0RXBUF;                 // Move RX data to address PRxData
    if (RXByteCtr == 1)                     // Only one byte left?
      UCB0CTL1 |= UCTXSTP;                  // Generate I2C stop condition
  }
  else
  {
    *PRxData = UCB0RXBUF;                   // Move final RX data to PRxData
    __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
  }
}