[参考译文] MSP430FR5994：更改UART的Tx/Rx引脚

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/1091481/msp430fr5994-changing-tx-rx-pins-for-uart

我正在为 MSP430FR5994 (特别是 MSP-EXP430FR5994)编写一些代码，并且我正在按照 示例代码发送PC信号并返回。 为了使用EXP板上的USB端口，我需要将UART引脚从WFP 6.0 和6.1 更改为2.0 WFP和WFP 2.1。 下面是我为实现此目标而更改的代码。

#include <msp430.h>

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


    // Configure GPIO
    P2SEL0 &= ~(BIT0 | BIT1);
    P2SEL1 |= (BIT0 | BIT1);                // USCI_A0 UART operation (p93_s)
    P6SEL1 &= ~(BIT0 | BIT1);
    P6SEL0 |= (BIT0 | BIT1);                // USCI_A3 UART operation (p109_s)

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

    // Startup clock system with max DCO setting ~8MHz
    CSCTL0_H = CSKEY_H;                       // Unlock CS registers
    CSCTL1 = DCOFSEL_3 | DCORSEL;             // Set DCO to 8MHz
    CSCTL2 = SELA__VLOCLK | SELS__DCOCLK | SELM__DCOCLK;
    CSCTL3 = DIVA__1 | DIVS__1 | DIVM__1;     // Set all dividers
    CSCTL0_H = 0;                             // Lock CS registers

    // Configure USCI_A3 for UART mode
    //UCA3CTLW0 = UCSWRST;                      // Put eUSCI in reset (p788)
    //UCA3CTLW0 |= UCSSEL__SMCLK;               // CLK = SMCLK
    // Baud Rate calculation
    // 8000000/(16*9600) = 52.083
    // Fractional portion = 0.083
    // User's Guide Table 21-4: UCBRSx = 0x04
    // UCBRFx = int ( (52.083-52)*16) = 1
    //UCA3BRW = 52;                             // 8000000/16/9600, BRW = Baud Rate Ctrl Word Register, p789
    //UCA3MCTLW |= UCOS16 | UCBRF_1 | 0x4900;   // UCOS16 = Oversampling enable, used when high frequency clk is used, probably divides everything by 16, UCBRF = fine turner when UCOS16 is active
                                              // 0x4900 is for first 8 bits,
    //UCA3CTLW0 &= ~UCSWRST;                    // Initialize eUSCI
    //UCA3IE |= UCRXIE;                         // Enable USCI_A3 RX interrupt

    // Configure USCI_A0 for UART mode
    UCA0CTLW0 = UCSWRST;                    // Put eUSCI in reset (p788)
    UCA0CTLW0 |= UCSSEL__SMCLK;             // CLK = SMCLK
    // Baud Rate calculation for 19200
    // 8000000/(16*19200) = 26.042
    // Fractional portion = 0.042
    // User's Guide Table 21-4: UCBRSx = 0x04
    // UCBRFx = int ( (52.083-52)*16) = 1
    UCA0BRW = 52;                           // 8000000/16/9600, BRW = Baud Rate Ctrl Word Register, p789
    UCA0MCTLW |= UCOS16 | UCBRF_1 | 0x4900; // UCOS16 = Oversampling enable, used when high frequency clk is used, probably divides everything by 16, UCBRF = fine turner when UCOS16 is active
                                              // 0x4900 is for first 8 bits,
    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=EUSCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(EUSCI_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));  //While the A0 flag and TX flag are not both active
            UCA0TXBUF = UCA0RXBUF;
            __no_operation();
            break;
        case USCI_UART_UCTXIFG: break;
        case USCI_UART_UCSTTIFG: break;
        case USCI_UART_UCTXCPTIFG: break;
        default: break;
    }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=EUSCI_A3_VECTOR
__interrupt void USCI_A3_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(EUSCI_A3_VECTOR))) USCI_A3_ISR (void)
#else
#error Compiler not supported!
#endif
{
    switch(__even_in_range(UCA3IV, USCI_UART_UCTXCPTIFG))
    {
        case USCI_NONE: break;
        case USCI_UART_UCRXIFG:
            while(!(UCA3IFG&UCTXIFG));  //While the A3 flag and TX flag are not both active
            UCA3TXBUF = UCA3RXBUF;
            __no_operation();
            break;
        case USCI_UART_UCTXIFG: break;
        case USCI_UART_UCSTTIFG: break;
        case USCI_UART_UCTXCPTIFG: break;
        default: break;
    }
}

但是，我无法使用Termite将字符从我的PC传输到主板。 使用引脚6.0 和6.1 测试系统，并将GPIO引脚连接到J101引脚，这样可以有效地更改引脚。