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Writing strings to the UART
von Andreas H. (ahoesch)

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Hi all,

I am programming an ATMEGA2560 and am trying to send strings via UART0. 
Sending single characters works,
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void serial_writeChar0(unsigned char c)

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  {

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   while ( !(UCSR0A & (1 << UDRE0)) );

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   UDR0 = c;

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  }

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but sending a complete string

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void serial_writeString0(const char *s)

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  {

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  while (*s)

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    {

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      serial_writeChar0(*s);

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      s++;

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    }

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  }

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while (1)

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  {

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   serial_writeChar0('A');

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   serial_writeChar0('B');

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   serial_writeChar0('C');

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   serial_writeChar0('\n');

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   serial_writeString0("Some String");

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   delay_ms(500);

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  }

produces dirt on the terminal.
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SÿÿÿÿÿÿÿÿÿÿÿABC

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SÿÿÿÿÿÿÿÿÿÿÿABC

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SÿÿÿÿÿÿÿÿÿÿÿABC

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SÿÿÿÿÿÿÿÿÿÿÿABC

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SÿÿÿÿÿÿÿÿÿÿÿABC

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SÿÿÿÿÿÿÿÿÿÿÿABC

What the heck could be the problem?

Thanks a lot in advance!!

Andreas

  


  



  

  
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    Re: Writing strings to the UART
  


  

    

      von
      
        stefanus (Guest)
      
      


      
    


    

      
    

    

    

  
  


  

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Maybe the bitrate is not accurate enough. The R/C oscillator is not 
recommended for serial ports and some combinations of bitrates and 
chrystal also dont work stable. The datasheet contains tables with 
recommended combinations.

Another problem cause might be not matching number of stop bits on the 
two ends of the cable.

Instead of the while loop, I usually write:

loop_until_bit_is_set(UCSR0A, UDRE0);

I'm not usre if that makes any difference. Possibly not, but it's worth 
to try.

  


  




  

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    Re: Writing strings to the UART
  


  

    

      von
      
        Mark R.
        (stevestrong)
        
      
      


      
    


    

      
    

    

    

  
  


  

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It would be nice to see your timer settings clocking the UART0.
Quartz frequency? UART0 Baudrate?
What other tasks run in the background? Will the UART0 timer somehow 
re-configured or used for something else?

  


  




  

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