Colony

/**

 * Copyright (c) 2009 Colony Project

 *

 * Permission is hereby granted, free of charge, to any person

 * obtaining a copy of this software and associated documentation

 * files (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use,

 * copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following

 * conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 **/

/**

 * @file wireless_receive.c

 * @brief Wireless library receive functions

 *

 * Implementation of high level wireless communication.

 * This is the receive functions portion of the library.

 *

 * @author Colony Project, CMU Robotics Club

 **/

#include <string.h>

#include "wl_defs.h"

#include "wireless.h"

#include "xbee.h"

/**

 * Definition for wireless library receive packet structure

 *

 * Basic Buffer Packet:

 *   byte 1: length of data

 *   bytes 2-3: source

 *   bytes 4-n: data

 *

 * Other Buffer Packet:

 *   byte 1: length of data

 *   byte 2: group number

 *   bytes 3-4: source

 *   bytes 5-n: data

 *

 **/

extern uint8_t xbee_basic_buf[PACKET_BUFFER_SIZE];  // buffer for basic-group packets

extern uint8_t xbee_other_buf[PACKET_BUFFER_SIZE];  // buffer for non-basic-group packets

extern uint8_t basic_buf_first;        // beginning of first packet in basic buffer

extern uint8_t basic_buf_last;        // end of last packet in basic buffer

extern uint8_t other_buf_first; // beginning of first packet in other buffer

extern uint8_t other_buf_last;  // end of last packet in other buffer

// the receive functions

/**

 * @addtogroup wireless Wireless

 * @{

 **/

/**

 * the main receive function (similar to wl_do)

 * 

 * when called, this function will receive the next packet on the default packet group

 * it will also dispatch registered packet handler functions for any other packet groups it has received

 *

 * @param data an already-initialized array to store the default group packet data in

 * @param length the length of the initialized data array

 *

 * @return the length of the used portion of data array or error (<0)

 **/

int8_t wl_get(char *data, uint8_t length) {

  int8_t return_code = wl_dispatch(); // run dispatch of other packet groups

  if (return_code != 0)

    return return_code; // error, so end early

  return wl_get_basic(data, length); // get a basic packet

}

/**

 * function to receive only packets on the default group

 * this function is only meant to receive packets sent using wl_send_basic()

 * 

 * @param data an already-initialized array to store the default group packet data in

 * @param length the length of the initialized data array

 * 

 * @return the length of the used portion of data array or error (<0)

 **/

int8_t wl_get_basic(char *data, uint8_t length) {

    uint8_t buf_pos = basic_buf_first;        // start at beginning of first (oldest) basic packet

    uint8_t data_length = xbee_basic_buf[buf_pos];  // get packet length

    uint8_t packet_num;        // number of packet (may eventually be used to weed out duplicates)

    if (data_length > length)        // not enough room for packet in destination

        return WL_ERROR_TOO_SMALL;

    buf_pos++;

    packet_num = xbee_basic_buf[buf_pos];   // get packet number

    buf_pos++;

    buf_pos++;        // ignore the group code. it will always be the same.

    memcpy(data, xbee_basic_buf + buf_pos, data_length);    // get the data

    basic_buf_first += data_length; // "free up" this packet's buffer space

    return 0;

}

/*

 * function to dispatch all registered packet handlers for received packets on non-default groups

 *

 * @return error codes (TBD)

 */

int8_t wl_dispatch(void) {

  return 0;

}

/**@} **/ //end defgroup

// Define all private functions down here