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

 *   Copyright (C) 2011 by Claas Anders "CaScAdE" Rathje                    *

 *   admiralcascade@gmail.com                                               *

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

 *                                                                          *

 *   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 "usart0.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;

/**

 * init usart0

 */

void usart0_init() {

    UBRR0H = ((F_CPU / (16UL * USART0_BAUD)) - 1) >> 8;

    UBRR0L = (F_CPU / (16UL * USART0_BAUD)) - 1;

    // Enable receiver and transmitter; enable RX interrupt

    UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);

    // set asynchronous mode

    UCSR0C &= ~(1 << UMSEL01);

    UCSR0C &= ~(1 << UMSEL00);

    // no parity

    UCSR0C &= ~(1 << UPM01);

    UCSR0C &= ~(1 << UPM00);

    // 1 stop bit

    UCSR0C &= ~(1 << USBS0);

    // 8-bit

    UCSR0B &= ~(1 << UCSZ02);

    UCSR0C |= (1 << UCSZ01);

    UCSR0C |= (1 << UCSZ00);

    // set direction of RXD0 and TXD0 pins

    // set RXD0 (PD0) as an input pin

    PORTD &= ~(1 << PORTD0);

    DDRD &= ~(1 << DDD0);

    // set TXD0 (PD1) as an output pin

    //PORTD |= (1 << PORTD1);

    //DDRD &= ~(1 << DDD1);

}

/**

 * disable the txd pin of usart0

 */

void usart0_DisableTXD(void) {

    UCSR0B &= ~(1 << TXCIE0); // disable TX-Interrupt

    UCSR0B &= ~(1 << TXEN0); // disable TX in USART

    DDRD &= ~(1 << DDD1); // set TXD pin as input

    PORTD &= ~(1 << PORTD1); // disable pullup on TXD pin

}

/**

 * enable the txd pin of usart0

 */

void usart0_EnableTXD(void) {

    DDRD |= (1 << DDD1); // set TXD pin as output

    PORTD &= ~(1 << PORTD1); // disable pullup on TXD pin

    UCSR0B |= (1 << TXEN0); // enable TX in USART

    UCSR0B |= (1 << TXCIE0); // enable TX-Interrupt

}

/**

 * send a single <character> through usart0

 */

void usart0_putc(unsigned char character) {

    // wait until UDR ready

    while (!(UCSR0A & (1 << UDRE0)));

    UDR0 = character;

}

/**

 * send a <string> throught usart0

 */

void usart0_puts(char *s) {

    while (*s) {

        usart0_putc(*s);

        s++;

    }

}

/**

 * send a PGM<string> throught usart0

 */

void usart0_puts_pgm(const char* string) {

    while (pgm_read_byte(string) != 0x00)

        usart0_putc(pgm_read_byte(string++));

}

/**

 * transmit interrupt handler

 * unused

 */

ISR(USART0_TX_vect, ISR_BLOCK) {

}

/*

 * receive data through usart0

 * portions taken and adapted from

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

 */

ISR(USART0_RX_vect, ISR_BLOCK) {

    uint8_t c;

    // catch the received byte

    c = UDR0;

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

    static uint16_t crc;

    static uint8_t ptr_rxd_buffer = 0;

    static uint8_t c1 = 0;

    static uint8_t c2 = 0;

    static uint8_t usart_rx_ok = 0;

    uint8_t crc1, crc2;

    // the rxd buffer is unlocked

    if (usart_rx_ok == 0) {

        // if ((c2 == '#') && (c1 == 'b' || c1 == 'c') && (c == 'D' || c == 'V' || c == 'O')) {

        if ((c2 == '#') && (c1 == 'b' || c1 == 'c') &&

#if FCONLY

            (c == 'V' || c == 'D' || c == 'Q' || c == 'L')) { // version, debug, settings, LCD

#else

            (c == 'V' || c == 'O' || c == 'Q')) { // version, OSD, settings

#endif

                usart_rx_ok = 1;

                rxd_buffer[ptr_rxd_buffer++] = c2;

                crc = c2;

                rxd_buffer[ptr_rxd_buffer++] = c1;

                crc += c1;

                rxd_buffer[ptr_rxd_buffer++] = c;

                crc += c;

                c2 = 0;

                c1 = 0;

            } else {

            c2 = c1;

            c1 = c;

        }

    } 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

                if (rxd_buffer[2] == 'R') {

                    wdt_enable(WDTO_250MS); // Reset-Commando

                }

            } else { // checksum invalid

                rxd_buffer_locked = 0; // unlock rxd buffer

            }

            ptr_rxd_buffer = 0; // reset rxd buffer pointer

            usart_rx_ok = 0;

        }

    } else { // rxd buffer overrun

        ptr_rxd_buffer = 0; // reset rxd buffer

        rxd_buffer_locked = 0; // unlock rxd buffer

        usart_rx_ok = 0;

    }

}

/**

 * 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';

    usart0_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 usart0_request_mk_data(uint8_t address, char label, uint8_t ms) {

    // re-enable TXD pin

    usart0_EnableTXD();

    unsigned char mstenth = ms / 10;

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

    // wait until UDR ready

    while (!(UCSR0A & (1 << UDRE0)));

    // disable TXD pin again

    usart0_DisableTXD();

}