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leventeyigel52
leventeyigel52
Associate III
July 25, 2012
Question

Change the USART Baudrate !

  • July 25, 2012
  • 6 replies
  • 901 views
Posted on July 25, 2012 at 20:37

Hello I want to change the USART baudrate in some conditions but i couldn't do this.

switch( bdstate)

          {

            case 0 :

              DownloadUsartConfig(9600);

              break;

            case 1 :

             DownloadUsartConfig(19200);

              break;

            case 2 :

              DownloadUsartConfig(38400);

              break;

            case 3 :

              DownloadUsartConfig(57600);

              break;

            case 4 :

              DownloadUsartConfig(115200);

              break;

            default:

              break ; 

          

          

          }

the function is :

void DownloadUsartConfig(uint32_t baudrate)

{

  USART_InitStructure.USART_BaudRate = baudrate;

  USART_InitStructure.USART_WordLength = USART_WordLength_8b;

  USART_InitStructure.USART_StopBits = USART_StopBits_1;

  USART_InitStructure.USART_Parity = USART_Parity_No;

  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

  

  /* Configure USART2 */

  USART_Init(DL_USART, &USART_InitStructure);

  

  USART_ITConfig(DL_USART, USART_IT_RXNE, ENABLE);

  /* Enable the USART2 */

  USART_Cmd(DL_USART, ENABLE);

}

it doesn't work 

How can do about the this problem ? Where doing i  make  mistake ?
    This topic has been closed for replies.

    6 replies

    Tesla DeLorean
    Tesla DeLorean
    Guru
    July 25, 2012
    Posted on July 25, 2012 at 20:52

    I would think just doing the USART_Init() portion would be sufficient, I swear I've done this before when downshifting the CORE/APB clocks.

    What you'd want to be sure of is that you aren't actively transmitting, ie wait for TC and TXE, so you don't change mid symbol.

    Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..
    leventeyigel52
    leventeyigel52Author
    Associate III
    July 25, 2012
    Posted on July 25, 2012 at 21:20

    I understood that 

    case 0 :

    USART_InitStructure.USART_BaudRate = 9600;

    USART_Init(DL_USART, &USART_InitStructure);

    break;

    case 1:

    USART_InitStructure.USART_BaudRate = 19200;

    USART_Init(DL_USART, &USART_InitStructure);

    break;

    ...

    ...

    Like it ?

    Andrew Neil
    Andrew Neil
    Super User
    July 26, 2012
    Posted on July 26, 2012 at 20:14

    ''it doesn't work''

    That is not a useful description of the problem!

    Do you mean it sets the wrong baud rate? Or sets it, but won't change it? Or the UART doesn't work at all? Or what??

    What debugging have you done to locate the problem?

    Have you started with a basic, working example on DevKit or Discovery Board or similar?

    http://www.catb.org/~esr/faqs/smart-questions.html

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
    leventeyigel52
    leventeyigel52Author
    Associate III
    July 26, 2012
    Posted on July 26, 2012 at 20:54

    Everything is ok

    At the first the baudrate must be 9600 and than it will be change in some conditions.

    when i changed the bd on the source code i saw the signals like noise ?

    Scope can't decode this signals .. 

    Andrew Neil
    Andrew Neil
    Super User
    July 26, 2012
    Posted on July 27, 2012 at 00:40

    ''Everything is ok''

    You mean the problem is now solved?
    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
    leventeyigel52
    leventeyigel52Author
    Associate III
    July 27, 2012
    Posted on July 27, 2012 at 03:08

    No I'm trying still

    Only problem is changing baudrate. usart is working

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