mirror of https://github.com/wb2osz/direwolf.git
336 lines
9.1 KiB
C
336 lines
9.1 KiB
C
//
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// This file is part of Dire Wolf, an amateur radio packet TNC.
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//
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// Copyright (C) 2019 John Langner, WB2OSZ
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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#include "direwolf.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <assert.h>
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#include <string.h>
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#include "fx25.h"
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#include "fcs_calc.h"
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#include "textcolor.h"
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#include "audio.h"
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#include "gen_tone.h"
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//#define FXTEST 1 // To build unit test application.
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#ifndef FXTEST
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static void send_bytes (int chan, unsigned char *b, int count);
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static void send_bit (int chan, int b);
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#endif
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static int stuff_it (unsigned char *in, int ilen, unsigned char *out, int osize);
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static int number_of_bits_sent[MAX_RADIO_CHANS]; // Count number of bits sent by "fx25_send_frame" or "???"
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#if FXTEST
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static unsigned char preload[] = {
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'T'<<1, 'E'<<1, 'S'<<1, 'T'<<1, ' '<<1, ' '<<1, 0x60,
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'W'<<1, 'B'<<1, '2'<<1, 'O'<<1, 'S'<<1, 'Z'<<1, 0x63,
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0x03, 0xf0,
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'F', 'o', 'o', '?' , 'B', 'a', 'r', '?' , // '?' causes bit stuffing
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0, 0, 0 // Room for FCS + extra
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};
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int main ()
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{
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text_color_set(DW_COLOR_ERROR);
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dw_printf("fxsend - FX.25 unit test.\n");
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dw_printf("This generates 11 files named fx01.dat, fx02.dat, ..., fx0b.dat\n");
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dw_printf("Run fxrec as second part of test.\n");
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fx25_init (3);
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for (int i = 100 + CTAG_MIN; i <= 100 + CTAG_MAX; i++) {
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fx25_send_frame (0, preload, (int)sizeof(preload)-3, i);
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}
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exit(EXIT_SUCCESS);
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} // end main
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#endif
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/*-------------------------------------------------------------
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*
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* Name: fx25_send_frame
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*
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* Purpose: Convert HDLC frames to a stream of bits.
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*
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* Inputs: chan - Audio channel number, 0 = first.
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*
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* fbuf - Frame buffer address.
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*
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* flen - Frame length, before bit-stuffing, not including the FCS.
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*
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* fx_mode - Normally, this would be 16, 32, or 64 for the desired number
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* of check bytes. The shortest format, adequate for the
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* required data length will be picked automatically.
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* 0x01 thru 0x0b may also be specified for a specific format
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* but this is expected to be mostly for testing, not normal
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* operation.
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*
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* Outputs: Bits are shipped out by calling tone_gen_put_bit().
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*
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* Returns: Number of bits sent including "flags" and the
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* stuffing bits.
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* The required time can be calculated by dividing this
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* number by the transmit rate of bits/sec.
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* -1 is returned for failure.
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*
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* Description: Generate an AX.25 frame in the usual way then wrap
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* it inside of the FX.25 correlation tag and check bytes.
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*
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* Assumptions: It is assumed that the tone_gen module has been
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* properly initialized so that bits sent with
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* tone_gen_put_bit() are processed correctly.
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*
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* Errors: If something goes wrong, return -1 and the caller should
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* fallback to sending normal AX.25.
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*
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* This could happen if the frame is too large.
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*
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*--------------------------------------------------------------*/
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int fx25_send_frame (int chan, unsigned char *fbuf, int flen, int fx_mode)
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{
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if (fx25_get_debug() >= 3) {
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text_color_set(DW_COLOR_DEBUG);
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dw_printf ("------\n");
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dw_printf ("FX.25[%d] send frame: FX.25 mode = %d\n", chan, fx_mode);
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fx_hex_dump (fbuf, flen);
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}
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number_of_bits_sent[chan] = 0;
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// Append the FCS.
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int fcs = fcs_calc (fbuf, flen);
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fbuf[flen++] = fcs & 0xff;
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fbuf[flen++] = (fcs >> 8) & 0xff;
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// Add bit-stuffing.
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unsigned char data[FX25_MAX_DATA+1];
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const unsigned char fence = 0xaa;
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data[FX25_MAX_DATA] = fence;
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int dlen = stuff_it(fbuf, flen, data, FX25_MAX_DATA);
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assert (data[FX25_MAX_DATA] == fence);
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if (dlen < 0) {
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text_color_set(DW_COLOR_ERROR);
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dw_printf ("FX.25[%d]: Frame length of %d + overhead is too large to encode.\n", chan, flen);
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return (-1);
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}
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// Pick suitable correlation tag depending on
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// user's preference, for number of check bytes,
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// and the data size.
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int ctag_num = fx25_pick_mode (fx_mode, dlen);
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if (ctag_num < CTAG_MIN || ctag_num > CTAG_MAX) {
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text_color_set(DW_COLOR_ERROR);
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dw_printf ("FX.25[%d]: Could not find suitable format for requested %d and data length %d.\n", chan, fx_mode, dlen);
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return (-1);
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}
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uint64_t ctag_value = fx25_get_ctag_value (ctag_num);
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// Zero out part of data which won't be transmitted.
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// It should all be filled by extra HDLC "flag" patterns.
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int k_data_radio = fx25_get_k_data_radio (ctag_num);
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int k_data_rs = fx25_get_k_data_rs (ctag_num);
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int shorten_by = FX25_MAX_DATA - k_data_radio;
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if (shorten_by > 0) {
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memset (data + k_data_radio, 0, shorten_by);
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}
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// Compute the check bytes.
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unsigned char check[FX25_MAX_CHECK+1];
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check[FX25_MAX_CHECK] = fence;
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struct rs *rs = fx25_get_rs (ctag_num);
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assert (k_data_rs + NROOTS == NN);
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ENCODE_RS(rs, data, check);
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assert (check[FX25_MAX_CHECK] == fence);
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if (fx25_get_debug() >= 3) {
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text_color_set(DW_COLOR_DEBUG);
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dw_printf ("FX.25[%d]: transmit %d data bytes, ctag number 0x%02x\n", chan, k_data_radio, ctag_num);
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fx_hex_dump (data, k_data_radio);
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dw_printf ("FX.25[%d]: transmit %d check bytes:\n", chan, NROOTS);
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fx_hex_dump (check, NROOTS);
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dw_printf ("------\n");
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}
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#if FXTEST
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// Standalone text application.
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unsigned char flags[16] = { 0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e ,0x7e };
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char fname[32];
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snprintf (fname, sizeof(fname), "fx%02x.dat", ctag_num);
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FILE *fp = fopen(fname, "wb");
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fwrite (flags, sizeof(flags), 1, fp);
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//fwrite ((unsigned char *)(&ctag_value), sizeof(ctag_value), 1, fp); // No - assumes little endian.
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for (int k = 0; k < 8; k++) {
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unsigned char b = (ctag_value >> (k * 8)) & 0xff; // Should be portable to big endian too.
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fwrite (&b, 1, 1, fp);
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}
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#if 1
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for (int j = 8; j < 16; j++) { // Introduce errors.
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data[j] = ~ data[j];
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}
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#endif
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fwrite (data, k_data_radio, 1, fp);
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fwrite (check, NROOTS, 1, fp);
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fwrite (flags, sizeof(flags), 1, fp);
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fflush(fp);
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fclose (fp);
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#else
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// Normal usage. Send bits to modulator.
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// Temp hack for testing. Corrupt first 8 bytes.
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// for (int j = 0; j < 16; j++) {
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// data[j] = ~ data[j];
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// }
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for (int k = 0; k < 8; k++) {
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unsigned char b = (ctag_value >> (k * 8)) & 0xff;
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send_bytes (chan, &b, 1);
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}
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send_bytes (chan, data, k_data_radio);
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send_bytes (chan, check, NROOTS);
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#endif
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return (number_of_bits_sent[chan]);
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}
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#ifndef FXTEST
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static void send_bytes (int chan, unsigned char *b, int count)
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{
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for (int j = 0; j < count; j++) {
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unsigned char x = b[j];
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for (int k = 0; k < 8; k++) {
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send_bit (chan, x & 0x01);
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x >>= 1;
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}
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}
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}
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/*
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* NRZI encoding.
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* data 1 bit -> no change.
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* data 0 bit -> invert signal.
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*/
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static void send_bit (int chan, int b)
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{
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static int output[MAX_RADIO_CHANS];
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if (b == 0) {
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output[chan] = ! output[chan];
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}
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tone_gen_put_bit (chan, output[chan]);
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number_of_bits_sent[chan]++;
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}
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#endif // FXTEST
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/*-------------------------------------------------------------
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*
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* Name: stuff_it
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*
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* Purpose: Perform HDLC bit-stuffing and add "flag" octets in
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* preparation for the RS encoding.
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*
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* Inputs: in - Frame, including FCS, in.
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*
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* ilen - Number of bytes in.
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*
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* osize - Size of out area.
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*
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* Outputs: out - Location to receive result.
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*
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* Returns: Number of bytes needed in output area including one trailing flag.
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* -1 if it won't fit.
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*
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* Description: Convert to stream of bits including:
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* start flag
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* bit stuffed data, including FCS
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* end flag
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* Fill remainder with flag octets which might not be on byte boundaries.
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*
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*--------------------------------------------------------------*/
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#define put_bit(value) { \
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if (olen >= osize) return(-1); \
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if (value) out[olen>>3] |= 1 << (olen & 0x7); \
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olen++; \
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}
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static int stuff_it (unsigned char *in, int ilen, unsigned char *out, int osize)
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{
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const unsigned char flag = 0x7e;
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int ret = -1;
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memset (out, 0, osize);
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out[0] = flag;
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int olen = 8; // Number of bits in output.
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osize *= 8; // Now in bits rather than bytes.
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int ones = 0;
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for (int i = 0; i < ilen; i++) {
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for (unsigned char imask = 1; imask != 0; imask <<= 1) {
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int v = in[i] & imask;
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put_bit(v);
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if (v) {
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ones++;
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if (ones == 5) {
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put_bit(0);
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ones = 0;
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}
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}
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else {
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ones = 0;
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}
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}
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}
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for (unsigned char imask = 1; imask != 0; imask <<= 1) {
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put_bit(flag & imask);
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}
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ret = (olen + 7) / 8; // Includes any partial byte.
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unsigned char imask = 1;
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while (olen < osize) {
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put_bit( flag & imask);
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imask = (imask << 1) | (imask >> 7); // Rotate.
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}
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return (ret);
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} // end stuff_it
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// end fx25_send.c
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