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/****************************************************************************

 *   Copyright (C) 2009 by Claas Anders "CaScAdE" Rathje                    *

 *   admiralcascade@gmail.com                                               *

 *   Project-URL: http://www.mylifesucks.de/oss/c-osd/                      *

 *                                                                          *

 *   This program is free software; you can redistribute it and/or modify   *

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

 *   the Free Software Foundation; either version 2 of the License.         *

 *                                                                          *

 *   This program 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          *

 *   GNU General Public License for more details.                           *

 *                                                                          *

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

 *   along with this program; if not, write to the                          *

 *   Free Software Foundation, Inc.,                                        *

 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.              *

 ****************************************************************************/

#include <avr/io.h>

#include <avr/interrupt.h>

#include <util/delay.h>

#include "main.h"

#include "usart1.h"

volatile uint8_t rxd_buffer_locked = 0;

volatile uint8_t rxd_buffer[RXD_BUFFER_LEN];

volatile uint8_t txd_buffer[TXD_BUFFER_LEN];

volatile uint8_t ReceivedBytes = 0;

volatile uint8_t *pRxData = 0;

volatile uint8_t RxDataLen = 0;

/* ##########################################################################

 * USART stuff

 * ##########################################################################*/

/**

 * init usart1

 */

void usart1_init() {

    UBRR1H = ((F_CPU / (16UL * baud)) - 1) >> 8;

    UBRR1L = (F_CPU / (16UL * baud)) - 1;

    // Enable receiver and transmitter; enable RX interrupt

    UCSR1B = (1 << RXEN1) | (1 << TXEN1) | (1 << RXCIE1);

    //asynchronous 8N1

    UCSR1C = (1 << URSEL1) | (3 << UCSZ10);

}

/**

 * disable the txd pin of usart1

 */

void usart1_DisableTXD(void) {

	UCSR1B &= ~(1 << TXCIE1); // disable TX-Interrupt

	UCSR1B &= ~(1 << TXEN1); // disable TXD in USART

	DDRB &= ~(1<<DDB3); // set TXD pin as input

	PORTB &= ~(1 << PORTB3);

}

/**

 * enable the txd pin of usart1

 */

void usart1_EnableTXD(void) {

	DDRB |= (1<<DDB3); // set TXD pin as output

	PORTB &= ~(1 << PORTB3);

	UCSR1B |= (1 << TXEN1); // enable TX in USART

	UCSR1B |= (1 << TXCIE1); // disable TX-Interrupt

}

/**

 * send a single <character> through usart1

 */

void usart1_putc(unsigned char character) {

    // wait until UDR ready

    while (!(UCSR1A & (1 << UDRE1)));

    UDR1 = character;

}

/**

 * send a <string> throught usart1

 */

void usart1_puts(char *s) {

    while (*s) {

        usart1_putc(*s);

        s++;

    }

}

/**

 * receive data through usart1

 * portions taken and adapted from

 * http://svn.mikrokopter.de/mikrowebsvn/filedetails.php?repname=FlightCtrl&path=%2Fbranches%2FV0.72p+Code+Redesign+killagreg%2Fuart0.c

 */

ISR(SIG_USART1_RECV) {

    if (rxd_buffer_locked) return; // if rxd buffer is locked immediately return

    LED1_ON

            static uint16_t crc;

    static uint8_t ptr_rxd_buffer = 0;

    uint8_t crc1, crc2;

    uint8_t c;

    c = UDR1; // catch the received byte

    // the rxd buffer is unlocked

    if ((ptr_rxd_buffer == 0) && (c == '#')) // if rxd buffer is empty and syncronisation character is received

    {

		/*

		// skip other datasets

        if (ptr_rxd_buffer == 2 && rxd_buffer[ptr_rxd_buffer] != 'O') {

 			ptr_rxd_buffer = 0; // reset rxd buffer

        	rxd_buffer_locked = 0; // unlock rxd buffer

		}*/

		rxd_buffer[ptr_rxd_buffer++] = c; // copy 1st byte to buffer

        crc = c; // init crc

    } else if (ptr_rxd_buffer < RXD_BUFFER_LEN) // collect incomming bytes

    {

        if (c != '\r') // no termination character

        {

            rxd_buffer[ptr_rxd_buffer++] = c; // copy byte to rxd buffer

            crc += c; // update crc

        } else // termination character was received

        {

            // the last 2 bytes are no subject for checksum calculation

            // they are the checksum itself

            crc -= rxd_buffer[ptr_rxd_buffer - 2];

            crc -= rxd_buffer[ptr_rxd_buffer - 1];

            // calculate checksum from transmitted data

            crc %= 4096;

            crc1 = '=' + crc / 64;

            crc2 = '=' + crc % 64;

            // compare checksum to transmitted checksum bytes

            if ((crc1 == rxd_buffer[ptr_rxd_buffer - 2]) && (crc2 == rxd_buffer[ptr_rxd_buffer - 1])) { // checksum valid

                rxd_buffer[ptr_rxd_buffer] = '\r'; // set termination character

                ReceivedBytes = ptr_rxd_buffer + 1; // store number of received bytes

                rxd_buffer_locked = 1; // lock the rxd buffer

            } else { // checksum invalid

                rxd_buffer_locked = 0; // unlock rxd buffer

            }

            ptr_rxd_buffer = 0; // reset rxd buffer pointer

        }

    } else // rxd buffer overrun

    {

        ptr_rxd_buffer = 0; // reset rxd buffer

        rxd_buffer_locked = 0; // unlock rxd buffer

    }

    LED1_OFF

}

/**

 * Decode the recevied Buffer

 * portions taken and adapted from

 * http://svn.mikrokopter.de/mikrowebsvn/filedetails.php?repname=FlightCtrl&path=%2Ftags%2FV0.72p%2Fuart.c

 */

void Decode64(void) {

    uint8_t a, b, c, d;

    uint8_t x, y, z;

    uint8_t ptrIn = 3;

    uint8_t ptrOut = 3;

    uint8_t len = ReceivedBytes - 6;

    while (len) {

        a = rxd_buffer[ptrIn++] - '=';

        b = rxd_buffer[ptrIn++] - '=';

        c = rxd_buffer[ptrIn++] - '=';

        d = rxd_buffer[ptrIn++] - '=';

        x = (a << 2) | (b >> 4);

        y = ((b & 0x0f) << 4) | (c >> 2);

        z = ((c & 0x03) << 6) | d;

        if (len--) rxd_buffer[ptrOut++] = x;

        else break;

        if (len--) rxd_buffer[ptrOut++] = y;

        else break;

        if (len--) rxd_buffer[ptrOut++] = z;

        else break;

    }

    pRxData = &rxd_buffer[3];

    RxDataLen = ptrOut - 3;

}

/**

 * request Data through USART in special MK format by adding checksum and

 * encode data in modified Base64

 * portions taken and adapted from

 * http://svn.mikrokopter.de/mikrowebsvn/filedetails.php?repname=FlightCtrl&path=%2Ftags%2FV0.72p%2Fuart.c

 */

void sendMKData(unsigned char cmd, unsigned char addr, unsigned char *snd, unsigned char len) {

    unsigned int pt = 0;

    unsigned char a, b, c;

    unsigned char ptr = 0;

    txd_buffer[pt++] = '#'; // Start-Byte

    txd_buffer[pt++] = 'a' + addr; // Adress

    txd_buffer[pt++] = cmd; // Command

    while (len) {

        if (len) {

            a = snd[ptr++];

            len--;

        } else a = 0;

        if (len) {

            b = snd[ptr++];

            len--;

        } else b = 0;

        if (len) {

            c = snd[ptr++];

            len--;

        } else c = 0;

        txd_buffer[pt++] = '=' + (a >> 2);

        txd_buffer[pt++] = '=' + (((a & 0x03) << 4) | ((b & 0xf0) >> 4));

        txd_buffer[pt++] = '=' + (((b & 0x0f) << 2) | ((c & 0xc0) >> 6));

        txd_buffer[pt++] = '=' + (c & 0x3f);

    }

    // add crc

    unsigned int tmpCRC = 0, i;

    for (i = 0; i < pt; i++) {

        tmpCRC += txd_buffer[i];

    }

    tmpCRC %= 4096;

    txd_buffer[i++] = '=' + tmpCRC / 64;

    txd_buffer[i++] = '=' + tmpCRC % 64;

    txd_buffer[i++] = '\r';

    usart1_puts((char*) txd_buffer);

}

/**

 * short script to directly send a request thorugh usart including en- and disabling it

 * where <address> is the address of the receipient, <label> is which data set to request

 * and <ms> represents the milliseconds delay between data

 */

void usart1_request_mk_data(uint8_t address, char label, uint8_t ms) {

            // re-enable TXD pin

            usart1_EnableTXD();

            unsigned char mstenth = ms/10;

			sendMKData(label, address, &mstenth, 1);

            // disable TXD pin again

            usart1_DisableTXD();

}