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 uart.h

 *

 *	@brief Initializes UART functions using the UART hardware module

 *

 *	@author Kevin Woo (kwoo)

 */

#ifndef UART_H

#define UART_H

#include <avr/io.h>

#include <avr/interrupt.h>

#include <stdint.h>

/** **/

#define UART_TX_OFF 0

#define UART_TX_ON 1

/** @brief RX Pin for the UART **/

#define RX		_BV(PORTD0)

#define TX		_BV(PORTD1)

#define TX_EN	_BV(PORTD5)

/** @brief The most recently received byte **/

extern uint8_t received_byte;

/** @brief If the value in received_byte has been read or not **/

extern uint8_t byte_ready;

/** @brief Initializes the UART registers and sets it to the buad rate 

 *         which msut be the value that is defined in the datasheet 

 *         for any particular speed (ie: 51 -> 9600bps)

 **/

void init_uart(uint16_t baud);

/** @brief Gets latest byte and returns it in output_byte. If the byte 

 *         was already read, returns -1 otherwise it returns 0 

 **/

int8_t uart_get_byte(uint8_t *output_byte);

/** @brief Sends a character array of size size. If we are currently 

 *         transmitting it will block until the the current transmit 

 *         is done. 

 **/

void uart_send_byte(uint8_t data);

void uart_toggle_transmit(uint8_t state);

#endif

/********

 * 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 uart.c

 *	

 *	@brief Implements UART functionality in hardware

 *

 *	@author Kevin Woo (kwoo)

 */

#include "uart.h"

#include <util/delay.h>

#include <stdint.h>

uint8_t received_byte;     //Byte received

uint8_t byte_ready;        //New byte has been received

void init_uart(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;

}

int8_t uart_get_byte(uint8_t *output_byte) {

	if (byte_ready) {

		byte_ready = 0;

		*output_byte = received_byte;

		return 0;

	} else {

		return -1;

	}

}

void uart_send_byte(uint8_t data) {

	//Waits until current transmit is done

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

    // Enable writes and send

	uart_toggle_transmit(UART_TX_ON);

    UDR = data;

	return;

}

void uart_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

    uart_toggle_transmit(UART_TX_OFF);

}