/*****************************************************************************
 *                                                                           *
 *        **********                                                         *
 *       ************                                                        *
 *      ***        ***                                                       *
 *      ***   +++   ***                                                      *
 *      ***   + +   ***                                                      *
 *      ***   +                CHIPCON CC1010 Wireless audio project         *
 *      ***   + +   ***                                                      *
 *      ***   +++   ***         PacketDisassembler for the master unit       *
 *      ***       ***                                                        *
 *       ***********                                                         *
 *        *********                                                          *
 *                                                                           *
 *****************************************************************************
 * This source file is part of a software project for Full Duplex,           *
 * single-chip, wireless intercom, written for the CC1010 chip               *
 * (RF-transceiver chip with integrated 8051 micro-controller).              *
 *****************************************************************************
 * Author:              OAE                                                  *
 *****************************************************************************
 * Revision history:                                                         *
 *                                                                           *
 * $Log: PacketDisassembler.c,v $
 * Revision 1.1  2003/08/04 12:35:08  tos
 * Initial version in CVS.
 *
 *                                                                           *
 *                                                                           *
 ****************************************************************************/

#include <chipcon/reg1010.h>
#include <chipcon/cc1010eb.h>
#include <chipcon/hal.h>

// Define buffer constants
#define BUFFER_SIZE 256
#define BUFFER0 0
#define BUFFER1 1

// Set up RAM buffers for halDES() at absolute addresses
byte xdata receivebuffer0[BUFFER_SIZE] _at_ 0x0200;
byte xdata receivebuffer1[BUFFER_SIZE] _at_ 0x0300;

// Define constants
#define MSB 1
#define LSB 0

// Define buffer pointers
const byte xdata *receive_buffer_start_ptr0 = &receivebuffer0[0];
const byte xdata *receive_buffer_start_ptr1 = &receivebuffer1[0];
byte xdata *receive_buffer_read_ptr;

// Variables for receive buffer
byte buffercode;// Temporary variable to store bytes read from buffer
byte receivereadcounter = 0;
bit readytoreadbuffer = 0;
bit currentreceivebuffer = 0;

// Extern variables
extern byte decoderpredsample;

// Function prototypes
byte DpcmDecoder (byte dpcmcodein, bit msbits);


/**************************************************************************
* PacketDisassembler() - Routine for packet disassembling                 *
***************************************************************************
* Description:                                                            *
*   Used to read and decode (done by DpcmCodec()) received speech codes,  *
*   read from receive buffer, and return decoded PCM speech samples,      *
***************************************************************************
* Input arguments:                                                        *
*   None.                                                                 *
* Return value:                                                           *
*   byte: A decoded (predicted) unsigned PCM speech sample (0-255).       *
**************************************************************************/
byte PacketDisassembler()
{
    /* The first byte of a valid packet will contain an uncoded
    predicted sample that must be saved rather than decoded*/
    if (receivereadcounter == 0)
    {
        if (currentreceivebuffer == BUFFER0)
        {
            // Point to the second buffer element 
            receive_buffer_read_ptr = receive_buffer_start_ptr0 + 1;

            // Increment read counter
            receivereadcounter++;
        
            // Initialize readytoreadbuffer
            readytoreadbuffer = 0;

            // Save and return the received predicted sample
            return (decoderpredsample = *receive_buffer_start_ptr0);

        }// End if

        else// (currentreceivebuffer == BUFFER1)
        {
            // Point to the second buffer element 
            receive_buffer_read_ptr = receive_buffer_start_ptr1 + 1;

            // Increment read counter
            receivereadcounter++;
        
            // Initialize readytoreadbuffer
            readytoreadbuffer = 0;

            // Save and return the received predicted sample
            return (decoderpredsample = *receive_buffer_start_ptr1);

        }// End else        

    }// End if

    else// (receivereadcounter != 0)
    {     
        // Toggle readytoreadbuffer
        readytoreadbuffer =! readytoreadbuffer;

        if (readytoreadbuffer)
        {
            // Read encoded byte from current buffer position
            buffercode = *receive_buffer_read_ptr;

            // Decode the four MSB of the buffercode, return decoded sample
            return (DpcmDecoder(buffercode,MSB));

        }// End if

        else // (!readytoreadbuffer)
        {
            // Increment read counter
            receivereadcounter++;

            // Increment pointer
            receive_buffer_read_ptr++;

            // Decode the four LSB of the buffercode, return decoded sample
            return (DpcmDecoder(buffercode,LSB));

        }// End else

    }// End else

}// End function


/**************************************************************************
* InitializeDisassembler() - Initialization of the PacketDisassembler()   *
***************************************************************************
* Description:                                                            *
*   Used to reset and initialize the function PacketDisassembler(). This  *
*   is done by forcing the receivereadcounter to zero and switching       *
*   between the two receivebuffers                                        *
***************************************************************************
* Input arguments:                                                        *
*   None.                                                                 *
* Return value:                                                           *
*   None                                                                  *
**************************************************************************/
void InitializeDisassembler()
{
    receivereadcounter = 0;

    // Switch buffer
    currentreceivebuffer = !currentreceivebuffer;

}// End function


/**************************************************************************
* ResetReceiveBuffers() - Routine for resetting both receive buffers      *
***************************************************************************
* Description:                                                            *
*   Used to fill both receive buffers with NULL-samples                   *
***************************************************************************
* Input arguments:                                                        *
*   None.                                                                 *
* Return value:                                                           *
*   None.                                                                 *
**************************************************************************/
void ResetReceiveBuffers()
{
    // Define the total buffersize
    word totalbuffersize = 2*BUFFER_SIZE;

    // Copy buffer pointer to local pointer variable
    byte xdata *buffer_start_ptr = receive_buffer_start_ptr0;

    // Fill receive buffers with NULL-samples
    while(totalbuffersize--)
            *buffer_start_ptr++ = 0x00;

}// End function