usart.c

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/**
 * @file        usart.c
 * @brief       Serial interface functions
 * @author      Copyright (C) Peter Ivanov, 2010
 *
 * Created      2010-08-07 11:48:53
 * Last modify: 2010-08-07 11:51:36 ivanovp {Time-stamp}
 * Licence:     GPL
 */
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdio.h>

// Define baud rate
#define USART_UBBR_CALC(baud)   (F_CPU / ((baud << 4)) - 1u)
#define USART0_BAUD_RATE        (19200ul)
#define USART_PRINTF_BUF_SIZE   (128)

/**
 * Initialize UART. Baud rate is in USART0_BAUD_RATE.
 * @see USART0_BAUD_RATE
 */
void USART0_init (void)
{
    /* Set the baud rate */
    UBRR0H = (uint8_t) (USART_UBBR_CALC (USART0_BAUD_RATE) >> 8u);
    UBRR0L = (uint8_t) USART_UBBR_CALC (USART0_BAUD_RATE);

    /* set to 8 data bits, no parity, 1 stop bit */
    UCSR0C = (0 << USBS0) | (1 << UCSZ01) | (1 << UCSZ00);

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

/** 
 * Read one byte from serial port. It waits for the data.
 *
 * @return The received character.
 */
unsigned char USART0_getc (void)
{
    /* Wait for incoming data */
    while (!(UCSR0A & (1 << RXC0)));

    /* Return the data */
    return UDR0;
}

/**
 * Write one byte to the serial port.
 *
 * @param data Byte to send.
 */
void USART0_putc (unsigned char data)
{
    /* Wait for empty transmit buffer */
    while (!(UCSR0A & (1 << UDRE0)));

    /* Start transmission */
    UDR0 = data;
}

/**
 * Write a null-terminated string to the serial port.
 *
 * @param data String to send.
 */
void USART0_puts (const char *data)
{
    while (*data)
    {
        USART0_putc (*data);
        data++;
    }
}

/**
 * Printf function which uses UART interface to send.
 * Example:
<pre>
UART_printf ("Number: %02i\r\n", number);
</pre>
 *
 * @param fmt Printf format string. Example: "Value: %02i\r\n"
 */
void USART0_printf (const char *fmt, ...)
{
    static va_list valist;
    char buf[USART_PRINTF_BUF_SIZE];
    
    va_start (valist, fmt);
    vsnprintf (buf, sizeof (buf), fmt, valist);
    va_end (valist);    
    USART0_puts (buf);
}

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