Help me get string for stm8l152c8 through usart communication

[chuanut4]

Posted on September 13, 2014 at 08:33

I'm trying to get a string from usart to stm8l, but when i got 2byte char, the RXNE is clear, and i can't get anymore char.

My code is:

main

{

    

int8_t count = 0;

    getdata  = '''';

    while(1)

    {

        getdata[count++] = getchar();

        

        if(getdata[0]==0x0D&&getdata[1]==0x0A)

        {

          getdata[0]=getdata[1]=NULL; count=0;

        }

        if(getdata[count-1]==0x0A)

        {

          getdata[count-1]=NULL;

          getdata[count]=NULL;

 break;

}

    }

}

GETCHAR_PROTOTYPE

{

  char c = 0;

  

  /* ???????  */ 

  while (USART_GetFlagStatus(USART1, USART_FLAG_RXNE) == RESET); 

  

  /* ??????? */ 

  c = USART_ReceiveData8(USART1);

  

  USART_ClearFlag(USART1, USART_FLAG_RXNE);

  

  return (c); 

}

Please help if you have any idea!

Thanks so much!

[zzdz2]

Posted on September 13, 2014 at 10:25

  c = USART_ReceiveData8(USART1);

 

  

 

  USART_ClearFlag(USART1, USART_FLAG_RXNE);

 

I think you clear the RXNE flag twice here as reading data reg also clears it.

It may cause some problem.

Edit:

if(getdata[0]==0x0D&&getdata[1]==0x0A)

        {

          getdata[0]=getdata[1]=NULL; count=0;

        }

        if(getdata[count-1]==0x0A)

        {

          getdata[count-1]=NULL;

The above code can actually try to access getdata[-1], it's really not good.

[chuanut4]

Posted on September 13, 2014 at 10:58

I have deleted line '' USART_ClearFlag(USART1, USART_FLAG_RXNE);'' in GETCHAR prototype.

With code: 

if(getdata[0]==0x0D&&getdata[1]==0x0A)

        {

          getdata[0]=getdata[1]=NULL; count=0;

        }

        if(getdata[count-1]==0x0A)

        {

          getdata[count-1]=NULL;

I try to get the breakpage symbol, and in line ''getdata[count++] = getchar();''

I have increased count variable, so i won't get access ''getdata[-1] error''.

I try very much, evenwhen i dont care about RXNE flag, but I always get only 2 char. 

I'm very grateful if you can help me get a string to stm8l.

[zzdz2]

Posted on September 13, 2014 at 12:07

int8_t count = 0;

getdata = ''''; What is the actual size of getdata buffer, where declared.If it's not the buffer problem then I don't know what.

With code:

if(getdata[0]==0x0D&&getdata[1]==0x0A)

{

getdata[0]=getdata[1]=NULL; count=0;

}

if(getdata[count-1]==0x0A)

{

getdata[count-1]=NULL;}

I try to get the breakpage symbol, and in line ''getdata[count++] = getchar();''

I have increased count variable, so i won't get access ''getdata[-1] error''.

OK, but when you get 0x0d+0x0a, count is reset to zero ant then you access getdata[0-1].Baybe it should be:

if(getdata[0]==0x0D&&getdata[1]==0x0A)
{
getdata[0]=getdata[1]=NULL; count=0;
continue;
}

[chuanut4]

Posted on September 13, 2014 at 17:03

Thank you so much knik, you're so gracious!

I declared char getdata[32]. And i deleted all of code except line ''getdata[count++] = getchar();'' in while(1) to get data, but i just got 2 char when I debug.

Do u have any idea to resolve this problem.

[zzdz2]

Posted on September 14, 2014 at 11:17

Maybe baud rate is not set correctly, make sure you receive correct chars.

It may happen that you receive some garbage when data rates don't match.

[chuanut4]

Posted on September 14, 2014 at 14:04

Yes, I recieve the correct char. Baudrate is valid.

I think the data buffer of stm8l just only 2byte. But if it's right, how to recieve a string from usart! So difficult!