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hospodar
hospodar
Associate III
November 20, 2012
Question

UART example code for STM32F0

  • November 20, 2012
  • 60 replies
  • 11869 views
Posted on November 20, 2012 at 23:34

Hello,

I looking for some example code for communication between my ST-DISCOVERY F0 board and PC (UART). Can someone help me with it? I´m novice.

Thank you
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    60 replies

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    kasun_duminda92
    kasun_duminda92
    Associate II
    June 19, 2013
    Posted on June 19, 2013 at 19:44

    I am receiving and error while calling sscanf on the 'line_buffer' variable.

    main.c(168): error:  #167: argument of type ''volatile char *'' is incompatible with parameter of type ''const char *restrict''

    My code within the while loop;

        __WFI(); // Wait for an interrupt rather than grind endlessly

        if (line_valid) // A new line has arrived

        {

                // ProcessLine(line_buffer); // Do something with the line

                char str[20];

                int num;

                sscanf(line_buffer, ''%s %d'', str, &num);

        ......................

    What do you think is the error here?
    Tesla DeLorean
    Tesla DeLorean
    Guru
    June 19, 2013
    Posted on June 19, 2013 at 23:27

    What do you think is the error here?

    Sounds like a casting issue. The buffer can be changed by an interrupt, and is thus transient. You can apply a cast, or copy it someplace else.

    A more complex implementation would require multiple buffers, and enqueuing them
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    kasun_duminda92
    kasun_duminda92
    Associate II
    June 20, 2013
    Posted on June 20, 2013 at 05:09

    Thanks!

    hospodar
    hospodarAuthor
    Associate III
    September 17, 2013
    Posted on September 17, 2013 at 22:33

    In order to tx interrupt I wrote this function, which is placing characters from printf to FIFO buffer. It is calling fromfputc(int ch, FILE *f) function and works fine. 

    void
FIFO_PUT(
char
ch)
{
if
(COUNT < FIFO_SIZE)
{
FIFO[COUNT] = ch;
COUNT ++;
}
}

    The next function I wrote is this one. It should be sending a characters from FIFO buffer to USART. It is calling from interrupt handler. 

    void
FIFO_GET(
void
)
{
char
j;
char
ch;
for
(j=0;j<10; j++) 
{
ch = FIFO[j];
USART_SendData(USART1, ch);
ch = 0;
}
}

    In result, program is don't working. Characters from printf are correct placing to the FIFO but to USART is don't sending this characters. Any idea?
    Tesla DeLorean
    Tesla DeLorean
    Guru
    September 17, 2013
    Posted on September 17, 2013 at 23:16

    Any idea?

    USART_SendData() can only be used once per TXE interrupt, there's basically a single holding register so you can't stuff multiple bytes in there.

    Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..
    hospodar
    hospodarAuthor
    Associate III
    October 6, 2013
    Posted on October 06, 2013 at 23:24

    Ok, so I replace this piece of code in interrupt handler with one from USART interrupt example for STM32F.. But it still don´t send any data to serial terminal. 

    if (USART_GetITStatus(USART
1
, USART_IT_TXE) != RESET)
{
USART_SendData(USART
1
, FIFO[tx_index++]);
if(tx_index == FIFO_SIZE)
{
/* Disable the USARTx Transmit interrupt */
USART_ITConfig(USART
1
, USART_IT_TXE, DISABLE);
} 
}

    bruno
    bruno
    Visitor II
    October 15, 2013
    Posted on October 15, 2013 at 19:05

    Thanks Ivan and Clive1. Your discussion helped me a lot to make a project running with Uart in interrupt mode with I/O buffers.

    I think the only thing missing to Ivan to get his application running (perhaps it's running today), was to manage the stop and go of the TXE interrupt (thrown when the TX buffer is empty).

    In the TXE interrupt when the buffer is empty, I  have disable the TXE interrupt as soon as the transmit buffer is empty (in the interrupt routine). Then, as soon as a new char arrives in the buffer (fputc), I enable again the interrupt if it is in disable mode. It's working fine...

    Thanks again to both of you for you pieces of code.

    Bruno.

    daniel2
    daniel2
    Associate III
    February 11, 2014
    Posted on February 11, 2014 at 16:16

    With this code: 

    if (USART_GetITStatus(USART1, USART_IT_TXE) != RESET) // Transmit the string in a loop
{
USART_SendData(USART1, StringLoop[tx_index++]);
if (tx_index >= (sizeof(StringLoop) - 1))
tx_index = 0;
}

    The UART interrupt keeps triggering endlessly unless I do something like else { disable interrupt}. Is there a better way to get it to stop triggering?
    daniel2
    daniel2
    Associate III
    February 11, 2014
    Posted on February 11, 2014 at 16:16

    With this code: 

    if (USART_GetITStatus(USART1, USART_IT_TXE) != RESET) // Transmit the string in a loop
{
USART_SendData(USART1, StringLoop[tx_index++]);
if (tx_index >= (sizeof(StringLoop) - 1))
tx_index = 0;
}

    The UART interrupt keeps triggering endlessly unless I do something like else { disable interrupt}. Is there a better way to get it to stop triggering?
    Tesla DeLorean
    Tesla DeLorean
    Guru
    February 11, 2014
    Posted on February 11, 2014 at 16:19

    If you don't have any data to send you need to disable the TXE interrupt.

    If you don't service a pending/enabled RXNE interrupt, the service routine will also continue to re-enter.

    Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..
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