/******************************************************************************
 * Function:        byte getsUSBUSART(char *buffer,
 *                                    byte len)
 *
 * PreCondition:    Value of input argument 'len' should be smaller than the
 *                  maximum endpoint size responsible for receiving bulk
 *                  data from USB host for CDC class.
 *                  Input argument 'buffer' should point to a buffer area that
 *                  is bigger or equal to the size specified by 'len'.
 *
 * Input:           buffer  : Pointer to where received bytes are to be stored
 *                  len     : The number of bytes expected.
 *
 * Output:          The number of bytes copied to buffer.
 *
 * Side Effects:    Publicly accessible variable cdc_rx_len is updated with
 *                  the number of bytes copied to buffer.
 *                  Once getsUSBUSART is called, subsequent retrieval of
 *                  cdc_rx_len can be done by calling macro mCDCGetRxLength().
 *
 * Overview:        getsUSBUSART copies a string of bytes received through
 *                  USB CDC Bulk OUT endpoint to a user's specified location. 
 *                  It is a non-blocking function. It does not wait
 *                  for data if there is no data available. Instead it returns
 *                  '0' to notify the caller that there is no data available.
 *
 * Note:            If the actual number of bytes received is larger than the
 *                  number of bytes expected (len), only the expected number
 *                  of bytes specified will be copied to buffer.
 *                  If the actual number of bytes received is smaller than the
 *                  number of bytes expected (len), only the actual number
 *                  of bytes received will be copied to buffer.
 *****************************************************************************/
byte getsUSBUSART(char *buffer, byte len)
{
    cdc_rx_len = 0;
    
    if(!mCDCUsartRxIsBusy())
    {
        /*
         * Adjust the expected number of bytes to equal
         * the actual number of bytes received.
         */
        if(len > CDC_BULK_BD_OUT.Cnt)
            len = CDC_BULK_BD_OUT.Cnt;
        
        /*
         * Copy data from dual-ram buffer to user's buffer
         */
        for(cdc_rx_len = 0; cdc_rx_len < len; cdc_rx_len++)
            buffer[cdc_rx_len] = cdc_data_rx[cdc_rx_len];

        /*
         * Prepare dual-ram buffer for next OUT transaction
         */
        CDC_BULK_BD_OUT.Cnt = sizeof(cdc_data_rx);
        mUSBBufferReady(CDC_BULK_BD_OUT);
    }//end if
    
    return cdc_rx_len;
    
}//end getsUSBUSART