MSP430FR2476: MSP430FR2476TRHB UART0 TXD

Can you try the example first. All of them is using UCA0. If you want to change the GPIO, please check this code. 

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 *                       MSP430 CODE EXAMPLE DISCLAIMER
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 * demonstrate a single peripheral function or device feature in a highly
 * concise manner. For this the code may rely on the device's power-on default
 * register values and settings such as the clock configuration and care must
 * be taken when combining code from several examples to avoid potential side
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//******************************************************************************
//  MSP430FR267x Demo - eUSCI_A0 UART echo at 4800 baud using BRCLK = 32768Hz.
//
//  Description: This demo echoes back characters received via a PC serial port.
//  ACLK is used as UART clock source and the device is put in LPM3.
//  Note that level shifter hardware is needed to shift between RS232 and MSP
//  voltage levels.
//
//  The example code shows proper initialization of registers
//  and interrupts to receive and transmit data.
//  To test code in LPM3, disconnect the debugger.
//
//  ACLK = REFO = 32768Hz, MCLK = SMCLK = DCODIV ~1MHz.
//
//                MSP430FR2676
//             -----------------
//         /|\|                 |
//          | |                 |
//          --|RST              |
//            |                 |
//            |                 |
//            |     P5.2/UCA0TXD|----> PC (echo)
//            |     P5.1/UCA0RXD|<---- PC
//            |                 |
//
//   Longyu Fang
//   Texas Instruments Inc.
//   August 2018
//   Built with IAR Embedded Workbench v7.12.1 & Code Composer Studio v8.1.0
//******************************************************************************
#include <msp430.h>

void Init_GPIO();

int main(void)
{
  WDTCTL = WDTPW | WDTHOLD;                 // Stop watchdog timer

  // Configure GPIO
  Init_GPIO();

  PM5CTL0 &= ~LOCKLPM5;                     // Disable the GPIO power-on default high-impedance mode
                                            // to activate 1previously configured port settings

  // Configure UART pins
 // SYSCFG3|=USCIA0RMP;                       //Set the remapping source
  P1SEL0 |= BIT4 | BIT5;                    // set 2-UART pin as second function

  // Configure UART
  UCA0CTLW0 |= UCSWRST;
  UCA0CTLW0 |= UCSSEL_1;                    // set ACLK as BRCLK

  // Baud Rate calculation. Referred to UG 17.3.10
  // (1) N=32768/4800=6.827
  // (2) OS16=0, UCBRx=INT(N)=6
  // (4) Fractional portion = 0.827. Refered to UG Table 17-4, UCBRSx=0xEE.
  UCA0BR0 = 6;                              // INT(32768/4800)
  UCA0BR1 = 0x00;
  UCA0MCTLW = 0xEE00;

  UCA0CTLW0 &= ~UCSWRST;                    // Initialize eUSCI
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt

  __bis_SR_register(LPM3_bits|GIE);         // Enter LPM3, interrupts enabled
  __no_operation();                         // For debugger
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_A0_VECTOR))) USCI_A0_ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(UCA0IV,USCI_UART_UCTXCPTIFG))
  {
    case USCI_NONE: break;
    case USCI_UART_UCRXIFG:
      while(!(UCA0IFG&UCTXIFG));
      UCA0TXBUF = UCA0RXBUF;
      __no_operation();
      break;
    case USCI_UART_UCTXIFG: break;
    case USCI_UART_UCSTTIFG: break;
    case USCI_UART_UCTXCPTIFG: break;
    default: break;
  }
}

void Init_GPIO()
{
    P1DIR = 0xFF; P2DIR = 0xFF;
    P1REN = 0xFF; P2REN = 0xFF;
    P1OUT = 0x00; P2OUT = 0x00;
}