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//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2011,2013 John Langner, WB2OSZ
//
// 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, or
// (at your option) any later version.
//
// 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, see <http://www.gnu.org/licenses/>.
//
#include <stdio.h>
#include "direwolf.h"
#include "hdlc_send.h"
#include "audio.h"
#include "gen_tone.h"
#include "textcolor.h"
#include "fcs_calc.h"
static void send_control (int, int);
static void send_data (int, int);
static void send_bit (int, int);
static int number_of_bits_sent;
/*-------------------------------------------------------------
*
* Name: hdlc_send
*
* Purpose: Convert HDLC frames to a stream of bits.
*
* Inputs: chan - Audio channel number, 0 = first.
*
* fbuf - Frame buffer address.
*
* flen - Frame length, not including the FCS.
*
* Outputs: Bits are shipped out by calling tone_gen_put_bit().
*
* Returns: Number of bits sent including "flags" and the
* stuffing bits.
* The required time can be calculated by dividing this
* number by the transmit rate of bits/sec.
*
* Description: Convert to stream of bits including:
* start flag
* bit stuffed data
* calculated FCS
* end flag
* NRZI encoding
*
*
* Assumptions: It is assumed that the tone_gen module has been
* properly initialized so that bits sent with
* tone_gen_put_bit() are processed correctly.
*
*--------------------------------------------------------------*/
int hdlc_send_frame (int chan, unsigned char *fbuf, int flen)
{
int j, fcs;
number_of_bits_sent = 0;
#if DEBUG
text_color_set(DW_COLOR_DEBUG);
dw_printf ("hdlc_send_frame ( chan = %d, fbuf = %p, flen = %d )\n", chan, fbuf, flen);
fflush (stdout);
#endif
send_control (chan, 0x7e); /* Start frame */
for (j=0; j<flen; j++) {
send_data (chan, fbuf[j]);
}
fcs = fcs_calc (fbuf, flen);
send_data (chan, fcs & 0xff);
send_data (chan, (fcs >> 8) & 0xff);
send_control (chan, 0x7e); /* End frame */
return (number_of_bits_sent);
}
/*-------------------------------------------------------------
*
* Name: hdlc_send_flags
*
* Purpose: Send HDLC flags before and after the frame.
*
* Inputs: chan - Audio channel number, 0 = first.
*
* nflags - Number of flag patterns to send.
*
* finish - True for end of transmission.
* This causes the last audio buffer to be flushed.
*
* Outputs: Bits are shipped out by calling tone_gen_put_bit().
*
* Returns: Number of bits sent.
* There is no bit-stuffing so we would expect this to
* be 8 * nflags.
* The required time can be calculated by dividing this
* number by the transmit rate of bits/sec.
*
* Assumptions: It is assumed that the tone_gen module has been
* properly initialized so that bits sent with
* tone_gen_put_bit() are processed correctly.
*
*--------------------------------------------------------------*/
int hdlc_send_flags (int chan, int nflags, int finish)
{
int j;
number_of_bits_sent = 0;
#if DEBUG
text_color_set(DW_COLOR_DEBUG);
dw_printf ("hdlc_send_flags ( chan = %d, nflags = %d, finish = %d )\n", chan, nflags, finish);
fflush (stdout);
#endif
/* The AX.25 spec states that when the transmitter is on but not sending data */
/* it should send a continuous stream of "flags." */
for (j=0; j<nflags; j++) {
send_control (chan, 0x7e);
}
/* Push out the final partial buffer! */
if (finish) {
audio_flush();
}
return (number_of_bits_sent);
}
static int stuff = 0;
static void send_control (int chan, int x)
{
int i;
for (i=0; i<8; i++) {
send_bit (chan, x & 1);
x >>= 1;
}
stuff = 0;
}
static void send_data (int chan, int x)
{
int i;
for (i=0; i<8; i++) {
send_bit (chan, x & 1);
if (x & 1) {
stuff++;
if (stuff == 5) {
send_bit (chan, 0);
stuff = 0;
}
} else {
stuff = 0;
}
x >>= 1;
}
}
/*
* NRZI encoding.
* data 1 bit -> no change.
* data 0 bit -> invert signal.
*/
static void send_bit (int chan, int b)
{
static int output;
if (b == 0) {
output = ! output;
}
tone_gen_put_bit (chan, output);
number_of_bits_sent++;
}
/* end hdlc_send.c */
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