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msp432 baud rate

Luca Palombella
Intellectual 560 points

hi all,

some questions.

1)what is the higher clock frequency that i can give to Uart serial communication? If i have DCO at 24Mhz, can i set it? 

2)If i have smclk at 12Mhz, the baud rate is fixed to 9600? Can i change baudrate without change clock?

  • 0
    Guru 74080 points
    UART has 7MBaud as maximum transmit frequency and 24MHz as maximum input frequency. The baudrate can be set very flexible and is not fixed to 9600Baud. Look at the code examples and the Technical Reference Manual for more information.

    Dennis
  • 0 in reply to Dennis Eichmann
    TI__Mastermind 49692 points
    The maximum eUSCI input clock frequency in UART mode depends on the value of VCORE. The frequencies that Dennis mentioned above require VCORE to be 1.4V (refer to Table 5-35 in the datasheet).

    Also, you can change the baud rate without changing the clock frequency within a reasonable limit (e.g. BRCLK equal to 32.768 kHz can't support a baud rate of 115200). Depending on BRCLK frequency and the required baud rate, you'll have to change UCOS16, UCBRx, UCBRFx, and UCBRSx as shown by Table 22-5 in the TRM. Referring to this table, you can quickly modify the UART code examples to achieve the desired baud rate.

    Regards,

    James

    MSP Customer Applications
  • 0 in reply to James Evans
    Intellectual 560 points

    Ok thanks for the explanation. Another question:

    If my uart clock is set to 12Mhz (SMCLK), reading the table i can choose different baud rate changing parameters. 

    1)Different baud rate change only the communication speed right?

    2)If i want baudrate = 38400 i have (from table): UCOS16=1, UCBRx=19, UCBRFx=8, UCBRSx=0x65. Is it correct write as the code written below?

      // Configure UART
  (...)
  UCA0CTLW0 |= UCSSEL__SMCLK;             // 12Mhz
  UCA0BR0 = 19;                           // 12000000/16/38400
  UCA0BR1 = 0x00;
  UCA0MCTLW = 0x6500 | UCOS16 | 0x0080;
  (...)

  • 0 in reply to Luca Palombella
    Guru 74080 points

    Hi Luca!

    Luca Palombella said:
    Different baud rate change only the communication speed right?

    Yes, that is right.

    Luca Palombella said:
    If i want baudrate = 38400

    I did not test it, but from these tables...

    ...I would say it is:

    UCA0BRW   = 19; // Same as UCA0BR0 = 19; and UCA0BR1 = 0;
UCA0MCTLW = (0x6500 | 0x0080 | UCOS16);

    Same as yours.

    Dennis

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