• State TI Thinks Resolved
  • Locked Locked
  • Replies 11 replies
  • Answers 4 answers
  • Subscribers 80 subscribers
  • Views 850 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430FR5949: UART did not receive data properly

Siv M
Prodigy 90 points

Part Number: MSP430FR5949

Hi,

I am using UART protocol as command and response manner. So, whenever  the controller receives the command then only it responses. Earlier this function of protocol is okay with following configuration: Baud_Rate : 9600, Bits: 8, Stop_bit:1, Parity:None.

Now I am trying the same thing with Baud_rate:115200, Bits: 8, Stop_bit:1, Parity:None. But The UART receive buffer is not getting the command bytes properly on its first trial. In the first trial I got 0xff in UART receive buffer. When the command hitting the receive buffer on it's second time then only it receives the command bytes. 

I have no idea about this behaviour of UART receiver. So please help me to find the solution.

  • 0
    TI__Intellectual 2065 points

    Hi Siv,

    This is most likely an issue caused by different baud rates. You need to make sure both the controller and receiver have the same baud rate; if you only changed one to 115200 you will not get the correct data in the buffer.

    Best,
    Amruta 

  • 0 in reply to Amruta Deole
    Prodigy 90 points

    Yes, both transmitter and receiver are kept in same baud_rate only. Here my problem is that I can receive data in controller at the second attempt of the command. In the first attempt controller RXBUF is filled by 0xff. 

  • 0 in reply to Siv M
    Guru 42835 points

    I would check it with a scope. A glitch on the line that mimics a start-bit will cause this.

  • 0 in reply to Keith Barkley
    Prodigy 90 points

    Okay then how to overcome this error? Can you please explain which factor cause this type of problem and please help me to solve this.

  • 0 in reply to Siv M
    Guru 42835 points

    Since it is on the receive side it is coming from whatever is sending the data.

  • 0 in reply to Siv M
    TI__Intellectual 2065 points

    Have you looked at it with a scope? When you do, what are you seeing?

  • 0 in reply to Amruta Deole
    Prodigy 90 points

    Yes I do. I saw the data whatever sent by the transmitter at the receiver end/ RX pin of the controller. But in debug mode the RXBUF of controller filled with 0xff or some garbage characters. I couldn't figured out what functionality is missing in UART configuration. 

  • 0 in reply to Siv M
    Guru 42835 points

    Are you using an interrupt?

    Can you share your code?

  • 0 in reply to Keith Barkley
    Prodigy 90 points

    Yes I am using ISR for UART. Here I share my code. Please find the attachment.

    uint8_t uart_initialize(void)
{
    P3DIR = 0x01;
    P2SEL1 = 0x03;
    UCA0CTLW0 = 0x0081;
//    UCA0BRW =  104;                                                              /* 16MHz / 9600 Baud_rate set */
//    UCA0MCTLW = 0xD621;
    UCA0BRW =  0x0008;                                                              /* 16MHz / 115200 Baud_rate set */
    UCA0MCTLW = 0xF7A1;
    UCA0CTLW0 = 0x0080;
    UCA0IE = 0x0001;
    return 1;
}

/*
 * This function used to transmit the data Through UART
 */
uint8_t tx_dat(uint8_t dat)
{
    while(!(UCA0IFG & UCTXIFG));
    UCA0TXBUF = dat;

    return 1;
}

/*
 * This function used to receive the data Through UART
 */
uint8_t rx_dat()
{
    uint8_t rx_data = 0U;
    while(!(UCA0IFG & UCRXIFG));
    rx_data = UCA0RXBUF;
    return (rx_data);
}

/*
 * This function used as UART Interrupt calling function
 */
uint8_t uart_interrupt1(void)
{
    uint8_t dat_buf[250] = {0};
    volatile uint8_t rxd_data1;
    uint16_t  looper_151;

    for(looper_151 = 0U; looper_151 < 245; looper_151++)
    {
        rxd_data1 = rx_dat();
        if(rxd_data1 != (uint8_t)'!')
        {
            rxd_data1 &= 0xFF;
            dat_buf[looper_151] = rxd_data1;
        }
        else
        {
            looper_151 = 245U;
        }
    }
    (void)commands(dat_buf);
    return 1;
}

/*
 * UART Interrupt Service routine
 */
#pragma vector = USCI_A0_VECTOR
__interrupt void UART_A0_ISR(void)
{
    (void)uart_interrupt1();
}

  • 0 in reply to Siv M
    Guru 42835 points

    You should only read one byte at a time in the interrupt, return, and wait for the next one. Check out the UART examples in Resource Explorer.

    Remember Herbert Hawkins rules for interrupts:

    Hubert Hawkins: I'd like to get in, get on with it, get it over with, and get out. Get it?

    Ravenhurst: Got it.

    Hubert Hawkins: Good.

     -Hubert Hawkins’ first rule of interrupts. Danny Kaye in The Court Jester

  • 0 in reply to Keith Barkley
    TI__Intellectual 2065 points

    Yes, take it out of the loop and just read every time the interrupt occurs.

**Attention** This is a public forum