Hi all,

Last couple of days I have started with my Atmega 644 (still had it arround from a previous project which did not start).
However I am capable of building an blinking led (without troubles), based on delay.h I am not capable in adding a serial port interface.

On the net I have not found a lot of info for the 644, since it is a little different with its registers. I think I have set them all correctly, but as said I get strang output (after code snippet examples):

/*

A simple program to demonstrate the use of USART of AVR micro

Hardware:
   ATmega644 @ 20MHz

   Suitable level converter on RX/TX line
   Connected to PC via RS232
   PC Software :  Hyper terminal @ 9600 baud
               No Parity,1 Stop Bit,
               Flow Control = NONE

*/
#ifndef F_CPU
#define F_CPU 20000000UL
#endif

# define USART_BAUDRATE 9600
# define BAUD_PRESCALE ((( F_CPU) / (16UL * USART_BAUDRATE) )  - 1)

#include <avr/io.h>

//This function is used to initialize the USART
//at a given UBRR value

void USART_Init( unsigned int baud ) // Extracted function from the datasheet
{
    /* Set baud rate */
    UBRR0H = (unsigned char)(baud>>8);
    UBRR0L = (unsigned char)baud;
    /* Enable receiver and transmitter */
    UCSR0B = (1<<RXEN0)|(1<<TXEN0);
    /* Set frame format: 8data, 1stop bit */
    UCSR0C = (3<<UCSZ00);
}

//This function is used to read the available data from USART. This function will wait until data is
//available.
unsigned char USART_Receive( void ) // Extracted function from the datasheet
{
    /* Wait for data to be received */
    while ( !(UCSR0A & (1<<RXC0)) )
    ;
    /* Get and return received data from buffer */
    return UDR0;
}

//This function writes the given "data" to the USART which then transmit it via TX line
void USART_Transmit( unsigned char data ) // Extracted function from the datasheet
{
    /* Wait for empty transmit buffer */
    while ( !( UCSR0A & (1<<UDRE0)) )
    ;
    /* Put data into buffer, sends the data */
    UDR0 = data;
}

int main(void)
{
   //Variable Declaration
   char data;

   USART_Init(BAUD_PRESCALE);

   //Loop forever
   while(1)
   {
      //Read data
      data=USART_Receive();

      /* Now send the same data but but surround it in
      square bracket. For example if user sent 'a' our
      system will echo back '[a]'.
      */

      USART_Transmit('[');
      USART_Transmit(data);
      USART_Transmit(']');
   }
}

If I configure my realterm as such:
- 8bit
- 1 stop
- no flow ctrl
- no parity

And send the char "a" I get "RXQ" in return, where I would be expecting "[a]".
Can someone advise me what I am doing wrong. I have read all options in the datasheet, but I cannot figure out by myself.

Furthermore connecting tx and rx directly give response on the console like "a" or "b".

 

Yeay, solved. Switched to a ftdi 2232 module (which I thought initially was broken), everything works now.
I get the correct response "[a]"

So the program was correct as well as my register settings