Sériové komunikačné rozhranie: Rozdiel medzi revíziami

#include <avr/io.h>

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


int main (void)
{
   char ReceivedChar;

   /* Initialize UART */
                                                         
   UBRR0 = (unsigned char)BAUD_PRESCALE;                 // Set baud rate: Load the UBRR register

   UCSR0B = (1 << RXEN0) | (1 << TXEN0);                 // Enable receiver and transmitter

   UCSR0C = (1<<USBS0)|(3<<UCSZ00);                      // Set format: 8data, 2stop bit 

   for (;;)                                              // Loop forever
   {
      while ((UCSR0A & (1 << RXC0)) == 0)                // Wait for data to be received 
	  {
	    // Do nothing until data have been recieved and is ready to be read from UDR
	  }; 
      ReceivedChar = UDR0;                               // Fetch the recieved byte 

   
      while ( !( UCSR0A & (1<<UDRE0)) )                  // Wait for empty transmit buffer 
   	  {
	   // Do nothing until UDR is ready for more data to be written to it
	  };
      UDR0 = ReceivedChar+1;                             // Echo back the modified received byte 
   }


}

/* ************************************************************************* */
/* FileName          : serial.h                                              */
/* ************************************************************************* */
         void inituart( void );
         void sendchar( unsigned char );
unsigned char recchar( void );

/* ************************************************************************* */
/*                                                                           */
/* Description       : UART communication routines                           */
/*                     Based on AppNote AVR109 - Self-programming            */
/*                                                                           */
/* FileName          : serial.c                                              */
/*                                                                           */
/* ************************************************************************* */

#include <avr\io.h>

// Following calculation assumes that F_CPU is assigned in 'Project/Options'
#define BAUDRATE       9600      
#define BAUD_PRESCALE  (((F_CPU / (BAUDRATE * 16UL))) - 1)


/* definitions for UART control */      
                                        // Valid for ATmega328
#define	BAUD_RATE_REG	        UBRR0   // 
#define	UART_STATUS_REG		UCSR0A  // OK, checked (but also control reg.)
#define	UART_CONTROL_REG_B	UCSR0B  // OK, checked
#define UART_CONTROL_REG_C      UCSR0C  // Added for mode setting
#define	ENABLE_TRANSMITTER_BIT	TXEN0   // OK, checked
#define	ENABLE_RECEIVER_BIT	RXEN0   // OK, checked
#define DATA_REGISTER_EMPTY_BIT UDRE0   // Added, for possible speed-up
#define	TRANSMIT_COMPLETE_BIT	TXC0    // OK, checked
#define	RECEIVE_COMPLETE_BIT	RXC0    // OK, checked
#define	UART_DATA_REG		UDR0    // OK, checked


void inituart(void)
{
 BAUD_RATE_REG = (unsigned char)BAUD_PRESCALE;    // Set baud rate: Load the UBRR register

 UART_CONTROL_REG_B = (1 << ENABLE_RECEIVER_BIT)|
                    (1 << ENABLE_TRANSMITTER_BIT); // Enable receive + transmit 

 UART_CONTROL_REG_C = (3<<UCSZ00);                 // Added: Async. UART, None 
                                                   // Parity, 8-data, 1 stopbit
                                                   
}


void sendchar(unsigned char c)
{
  UART_DATA_REG = c;                                   // prepare transmission
  while (!(UART_STATUS_REG & (1 << TRANSMIT_COMPLETE_BIT)));// wait until byte sendt
  UART_STATUS_REG |= (1 << TRANSMIT_COMPLETE_BIT);          // delete TXCflag
}


unsigned char recchar(void)
{
  while( !(UART_STATUS_REG & (1 << RECEIVE_COMPLETE_BIT)) );  // wait for data
  return UART_DATA_REG;
}

#include <avr\io.h>
#include "serial.h"              // Nasa kniznica... 

int main(void) 
{
 char c;

  DDRD = 0b00000010;
 PORTD = 0b00000011;    // Set TxD pin as an output, RxD input
 
 inituart();

 sendchar('O');
 sendchar('K');
 sendchar('\n');

 for (c=32;c<=127;c++) 
   sendchar(c);

 for (;;) {
     /* Do nothing */
          }
}

...
#include <stdio.h>

FILE mystdout = FDEV_SETUP_STREAM(sendchar, NULL, _FDEV_SETUP_WRITE);
                              // 'sendchar' je nova funkcia pre jeden znak

int main(void)
{ 
 inituart();	               // Inicializacia seriovej linky
 stdout = &mystdout;           // Odteraz funguje printf();

 printf("Hello, world!");
 return 0;
}

FILE uart_output = FDEV_SETUP_STREAM(sendchar, NULL, _FDEV_SETUP_WRITE);
FILE uart_input = FDEV_SETUP_STREAM(NULL, recchar, _FDEV_SETUP_READ);

int main(void) {

    inituart();
    stdout = &uart_output;
    stdin = &uart_input;
                
    char input;

    while(1) {
        puts("Hello world!");
        input = getchar();
        printf("You wrote %c\n", input);
    }
        
    return 0;
}