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

Alex K. OP (Company: ---) #3803015
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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:

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#include <avr/io.h>

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#include <avr/interrupt.h>

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#include <util/delay.h>

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#include <stdlib.h>

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#include <compat/twi.h>

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#define FOSC 16000000     //Clock Speed

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#define BAUD 9600         //Baud rate set to 9600

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#define MYBRR FOSC/16/BAUD-1

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void USART_Init (void)

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{

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

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UBRRL = MYBRR;               //the baud rate

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

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

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

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}

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/* USART transmit function */

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void USART_Transmit(unsigned char data)

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{

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

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     UDR = data;

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}

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/* USART receive function */

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unsigned char USART_Receive(void)

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{

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

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

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}

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 int main(void)

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[c] {

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[c] unsigned char c;

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[c]while(1)

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{

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    a = USART_Receive();

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    c = 10;

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    USART_Transmit(c);

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    _delay(10000);

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}

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}


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.

  





  

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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:

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



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

>
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//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 */

>
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unsigned char USART_Receive(void)

>
1
{

>
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     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...

  





  

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