#include <msp430f5529.h>

unsigned char TXData;
unsigned char i=0;

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  P3SEL |= 0x03;                            // Assign I2C pins to USCI_B0
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMODE_3 + UCSYNC;             // I2C Slave, synchronous mode
  UCB0I2COA = 0x48;                         // Own Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  UCB0IE |= UCTXIE + UCSTTIE + UCSTPIE;     // Enable TX interrupt
                                            // Enable Start condition interrupt
  TXData = 0xAA;                               // Used to hold TX data

  __bis_SR_register(LPM0_bits + GIE);       // Enter LPM0 w/ interrupts
  __no_operation();                         // For debugger
}

// USCI_B0 State ISR
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
{
  switch(__even_in_range(UCB0IV,12))
  {
  case  0: break;                           // Vector  0: No interrupts
  case  2: break;                           // Vector  2: ALIFG
  case  4: break;                           // Vector  4: NACKIFG
  case  6:                                  // Vector  6: STTIFG
     UCB0IFG &= ~UCSTTIFG;                  // Clear start condition int flag
     break;
  case  8:                                  // Vector  8: STPIFG
    //TXData++;                               // Increment TXData
    UCB0IFG &= ~UCSTPIFG;                   // Clear stop condition int flag
    break;
  case 10: break;                           // Vector 10: RXIFG  
  case 12:                                  // Vector 12: TXIFG
    UCB0TXBUF = TXData;                     // TX data
    break;
  default: break;
  }
}

Кстати, а резисторы на шине к питанию MSP430 подтянуты или к другому напряжению? У FTDI на VССIO то же самое по величине напряжение, что и на MSP430 подается, надеюсь?

#include <msp430f5529.h>

unsigned char TXData;
void SetVcoreUp (unsigned int level);

void main(void)
{
  volatile unsigned int i;

  WDTCTL = WDTPW+WDTHOLD;                   // Stop WDT
  
  P1DIR |= 0x01;                            // Set P1.0 to output direction
  P1OUT  = 0x01;

  P1DIR |= BIT1;                            // P1.1 output

  P1DIR |= BIT0;                            // ACLK set out to pins
  P1SEL |= BIT0;                            
  P2DIR |= BIT2;                            // SMCLK set out to pins
  P2SEL |= BIT2;                            
  P7DIR |= BIT7;                            // MCLK set out to pins
  P7SEL |= BIT7;          

    //*********************   I2C  ****************************
  P3SEL |= 0x03;                            // Assign I2C pins to USCI_B0
  UCB1CTL1 |= UCSSEL1;
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMODE_3 + UCSYNC;             // I2C Slave, synchronous mode
  UCB0I2COA = 0x48;                         // Own Address is 048h
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  UCB0IE |= UCTXIE + UCSTTIE + UCSTPIE;     // Enable TX interrupt
                                            // Enable Start condition interrupt
  TXData = 0x7F;                            // Used to hold TX data

  //*********************************************************
  
  
  // Increase Vcore setting to level3 to support fsystem=25MHz
  // NOTE: Change core voltage one level at a time..
  SetVcoreUp (0x01);
  SetVcoreUp (0x02);  
  SetVcoreUp (0x03);  
  
  UCSCTL3 = SELREF_2;                       // Set DCO FLL reference = REFO
  UCSCTL4 |= SELA_2;                        // Set ACLK = REFO

  __bis_SR_register(SCG0);                  // Disable the FLL control loop
  UCSCTL0 = 0x0000;                         // Set lowest possible DCOx, MODx
  UCSCTL1 = DCORSEL_7;                      // Select DCO range 50MHz operation
  UCSCTL2 = FLLD_1 + 762;                   // Set DCO Multiplier for 25MHz
                                            // (N + 1) * FLLRef = Fdco
                                            // (762 + 1) * 32768 = 25MHz
                                            // Set FLL Div = fDCOCLK/2
  __bic_SR_register(SCG0);                  // Enable the FLL control loop

  // Worst-case settling time for the DCO when the DCO range bits have been
  // changed is n x 32 x 32 x f_MCLK / f_FLL_reference. See UCS chapter in 5xx
  // UG for optimization.
  // 32 x 32 x 25 MHz / 32,768 Hz ~ 780k MCLK cycles for DCO to settle
  __delay_cycles(782000);

  // Loop until XT1,XT2 & DCO stabilizes - In this case only DCO has to stabilize
  do
  {
    UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);
                                            // Clear XT2,XT1,DCO fault flags
    SFRIFG1 &= ~OFIFG;                      // Clear fault flags
  }while (SFRIFG1&OFIFG);                   // Test oscillator fault flag
  
  __bis_SR_register(GIE);       // Enter LPM0 w/ interrupts
  
  while(1)
  {}
}

void SetVcoreUp (unsigned int level)
{
  // Open PMM registers for write
  PMMCTL0_H = PMMPW_H;              
  // Set SVS/SVM high side new level
  SVSMHCTL = SVSHE + SVSHRVL0 * level + SVMHE + SVSMHRRL0 * level;
  // Set SVM low side to new level
  SVSMLCTL = SVSLE + SVMLE + SVSMLRRL0 * level;
  // Wait till SVM is settled
  while ((PMMIFG & SVSMLDLYIFG) == 0);
  // Clear already set flags
  PMMIFG &= ~(SVMLVLRIFG + SVMLIFG);
  // Set VCore to new level
  PMMCTL0_L = PMMCOREV0 * level;
  // Wait till new level reached
  if ((PMMIFG & SVMLIFG))
    while ((PMMIFG & SVMLVLRIFG) == 0);
  // Set SVS/SVM low side to new level
  SVSMLCTL = SVSLE + SVSLRVL0 * level + SVMLE + SVSMLRRL0 * level;
  // Lock PMM registers for write access
  PMMCTL0_H = 0x00;
}

// USCI_B0 State ISR
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
{
  switch(__even_in_range(UCB0IV,12))
  {
  case  0: break;                           // Vector  0: No interrupts
  case  2: break;                           // Vector  2: ALIFG
  case  4: break;                           // Vector  4: NACKIFG
  case  6:                                  // Vector  6: STTIFG
     UCB0IFG &= ~UCSTTIFG;                  // Clear start condition int flag
     break;
  case  8:                                  // Vector  8: STPIFG
    //TXData++;                               // Increment TXData
    UCB0IFG &= ~UCSTPIFG;                   // Clear stop condition int flag
    break;
  case 10: break;                           // Vector 10: RXIFG  
  case 12:                                  // Vector 12: TXIFG
    UCB0TXBUF = TXData;                     // TX data
    break;
  default: break;
  }
}