Tooltron

/********

 * This file is part of Tooltron.

 *

 * Tooltron is free software: you can redistribute it and/or modify

 * it under the terms of the Lesser GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * Tooltron is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * Lesser GNU General Public License for more details.

 * You should have received a copy of the Lesser GNU General Public License

 * along with Tooltron.  If not, see <http://www.gnu.org/licenses/>.

 *

 * Copyright 2009 Kevin Woo <kwoo@2ndt.com>

 *

 ********/

/** @file rs485_int.c

 *        

 *        @brief Implements UART functionality in hardware

 *

 *        @author Kevin Woo (kwoo)

 */

#include "rs485_int.h"

#include <util/delay.h>

#include <stdint.h>

uint8_t received_byte;     //Byte received

uint8_t byte_ready;        //New byte has been received

void rs485_init(uint16_t baud) {

        // Set baud rate

        UBRRH = (uint8_t)(baud>>8);

        UBRRL = (uint8_t)baud;

        // Enable RX/TX and RX/TX Interrupt

        UCSRB = _BV(RXCIE) | _BV(RXEN) | _BV(TXCIE) | _BV(TXEN);

        // Enable the TXEN pin as output

        DDRD |= TX_EN;

    // Initialize receive variables

    byte_ready = 0;

    received_byte = 0x0;

    // Set to receive mode

    rs485_toggle_transmit(TX_OFF);

}

int8_t rs485_get_byte(uint8_t *output_byte) {

        if (byte_ready) {

                byte_ready = 0;

                *output_byte = received_byte;

                return 0;

        } else {

                return -1;

        }

}

void rs485_send_byte(uint8_t data) {

        //Waits until current transmit is done

    while (!(UCSRA & _BV(UDRE)));

    // Enable writes and send

        rs485_toggle_transmit(UART_TX_ON);

    UDR = data;

        return;

}

void rs485_toggle_transmit(uint8_t state) {

        if (state == UART_TX_ON) {

                PORTD |= TX_EN;

        } else {

                PORTD &= ~TX_EN;

        }

}

ISR(USART_RX_vect) {

    received_byte = UDR;

    byte_ready = 1;    

}

ISR(USART_TX_vect) {

    // Re-enable reads

    rs485_toggle_transmit(UART_TX_OFF);

}