EmbDev.net

Forum: µC & Digital Electronics AVR ATmega8, cannot transmit multiple characters via UART, data getting lost


AVR ATmega8, cannot transmit multiple characters via UART, data getting lost
von Alex K. (Company: ---) (akap)

Rate this post
• ▲ useful
▼ not useful 
Hi,

I think I have a very simple problem, but as a beginner I cannot find a 
solution.

I am writing a code for a MCU until that will transmit data via UART 
(RS232). [ATmega8A]

Currently, I am testing my code in Proteus:

1
#include <avr/io.h>

1
#include <avr/interrupt.h>

1
#include <util/delay.h>

1
#include <stdlib.h>

1
#include <compat/twi.h>

1
#define FOSC 16000000     //Clock Speed

1
#define BAUD 9600         //Baud rate set to 9600

1
#define MYBRR FOSC/16/BAUD-1

1
void USART_Init (void)

1
{

1
UBRRH = (MYBRR >> 8);        //Code for setting

1
UBRRL = MYBRR;               //the baud rate

1
UCSRB = (1 << RXEN) | (1 << TXEN); //Enable receiver and transmitter

1
UCSRC = (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);

1
//Frame format setting: 8 Data, 2 Stop bit

1
}

1
/* USART transmit function */

1
void USART_Transmit(unsigned char data)

1
{

1
  while(!(UCSRA & (1 << UDRE)));//Wait until transmit buffer is empty

1
     UDR = data;

1
}

1
/* USART receive function */

1
unsigned char USART_Receive(void)

1
{

1
     while(!(UCSRA & (1 << RXC))); //Wait until data is received

1
     return UDR;   //Get the data from buffer and return it

1
}

1
 int main(void)

2
[c] {

3
[c] unsigned char c;

4
5
[c]while(1)

1
{

1
    a = USART_Receive();

1
    c = 10;

1
    USART_Transmit(c);

1
    _delay(10000);

1
}

1
}


n Proteus, the virtual terminal displays 0. However, I am expecting to 
see 10. This is just one example, in general only the last 
digit/character is getting displayed on the virtual terminal.
Same happens if I want to transmit say AA, only A will be displayed.
I cannot explain this. Proteus bug or logic error?

Thank you for any advise.

  


  




  

    Report post Edit Move Thread sperren Anmeldepflicht aktivieren Anpinnen Delete topic Thread mit anderem zusammenführen Quote selected text Reply Reply with quote
  







      

      



  

    Re: AVR ATmega8, cannot transmit multiple characters via UART, data getting lost
  


  

    

      von
      
        c-hater (Guest)
      
      


      
    


    

      
    

    

    

  
  


  

  Rate this post
  

  •
  
  ▲ useful 
  

  ▼ not useful 
  		
  

  


  

      
Alex Kapphahn wrote:

> Currently, I am testing my code in Proteus:

What, the f**k is Proteus? For what is it good for?


> I am writing a code for a MCU until that will transmit data via UART
> (RS232). [ATmega8A]

>
1
#define MYBRR FOSC/16/BAUD-1


Stupid, but may work. You should clarify your intention using braces.

>
1
#define MYBRR (FOSC/16)/BAUD-1


Much better is it with implicite rounding:

>
1
#define MYBRR (FOSC/16+BAUD/2)/BAUD-1



>
1
UCSRC = (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);

>
1
//Frame format setting: 8 Data, 2 Stop bit


Your code partially doesn't match the provided comment. Matches for 
number of data bits, but doesn't match for number of stop bits.


>
1
/* USART receive function */

>
1
unsigned char USART_Receive(void)

>
1
{

>
1
     while(!(UCSRA & (1 << RXC))); //Wait until data is received

>
>
1
     return UDR;   //Get the data from buffer and return it

>
1
}


Poor implementation. It doesn't care the possebility of transmission 
errors.


> n Proteus, the virtual terminal displays 0. However, I am expecting to
> see 10.

You shouldn't. If you send a char with value 10, you will receive a char 
with value 10 (in the case there is no transmission error and sender and 
receiver uses same frame format).

You can expect to get a visible "10" in the only case, the receiving 
terminal replaces received, but unprintable characters with decimal 
strings, describing their values.

> Proteus bug or logic error?

Probably your error. Either you made a mistake in your code or you don't 
understand what "Proteus" does. Whatever "Proteus" is...

  


  




  

    Report post Edit Delete Quote selected text Reply Reply with quote
  








    

    

       Watch this topic

      |
         Disable multi-page view

    

        


Please log in before posting. Registration is free and takes only a minute.



  Existing account

  


  
  

  
    

      

        
          
        
        
          
        
      

      

        
          
        
        
          
        
      

    


    
    
    





  Do you have a Google/GoogleMail account? No registration required!

  Log in with Google account
  





  No account? Register here.