MSP430FR5869: UART configuration

Hello,

Please add below code to activate the port setting, otherwise the GPIO is in high-impedance state.

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

Hi,

I have deactivated high-impedance state setting. My full code is below:

void config_uart(void)
{
    // Configure GPIO
    P2SEL1 |= BIT0 | BIT1;                    // USCI_A1 UART operation
    P2SEL0 &= ~(BIT0 | BIT1);

    UCA0CTLW0 = UCSWRST;                      // Put eUSCI in reset
    UCA0CTL1 |= UCSSEL__SMCLK;                // CLK = SMCLK
    UCA0BR0 = 8;                              // 1000000/115200 = 8.68
    UCA0MCTLW = 0xD600;                       // 1000000/115200 - INT(1000000/115200)=0.68
                                              // UCBRSx value = 0xD6 (See UG)
    UCA0BR1 = 0;
    UCA0CTL1 &= ~UCSWRST;                     // release from reset
    UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt
}

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;	// stop watchdog timer
    PM5CTL0 &= ~LOCKLPM5;
  
    config_uart();
    __bis_SR_register(GIE);

    while(1)
    {
        while (!(UCA0IFG&UCTXIFG));               // USCI_A0 TX buffer ready?
        UCA0TXBUF = 0;
        LPM0;
    }
    return 0;
}
 

Please refer to the code example.

https://dev.ti.com/tirex/explore/node?node=AJr9qX-CKoMI9Io-uCLayw__IOGqZri__LATEST

And it should be   

UCA0CTLW0 |= UCSSEL__SMCLK;               // CLK = SMCLK

Hi,

I am following this example code:

https://dev.ti.com/tirex/explore/node?node=AOT9wOr9FckXR1RzMAjv7g__IOGqZri__LATEST

Hi,

Another question is if I measured the output of TXD port on the MCU using oscilloscope I should observe bit pattern corresponding with the data bits I am sending from MCU. From my understanding if I am sending data continuously data observed should be bit pattern repeated that match the data value. Is this correct? Thank you.

Yes, it's correct. Did you capture the waveform when running example code?

Hi Winter,

I did not see any output on UART TXD when running the code. Because I am using the same UART port RXD for downloading firmware in BSL mode. Do you think this may cause problem with UART transmission? Thank you

I think may not be a problem. But you can try another UART port.