V.27ter Modem emulation (partly)
This commit is contained in:
parent
5070bc70bd
commit
6a18c924fb
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@ -48,6 +48,7 @@ src/libsample/libsample.a
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src/libam/libam.a
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src/libclipper/libclipper.a
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src/libserial/libserial.a
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src/libv27/libv27.a
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src/anetz/libgermanton.a
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src/anetz/anetz
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src/bnetz/bnetz
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@ -80,3 +81,4 @@ src/test/test_dms
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src/test/test_sms
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src/test/test_performance
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src/test/test_hagelbarger
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src/test/test_v27scrambler
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@ -85,6 +85,7 @@ AC_OUTPUT(
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src/libsample/Makefile
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src/libclipper/Makefile
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src/libserial/Makefile
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src/libv27/Makefile
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src/anetz/Makefile
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src/bnetz/Makefile
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src/cnetz/Makefile
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@ -26,7 +26,8 @@ SUBDIRS = \
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libfft \
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libmncc \
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libclipper \
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libserial
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libserial \
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libv27
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if HAVE_ALSA
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SUBDIRS += \
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@ -0,0 +1,9 @@
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AM_CPPFLAGS = -Wall -Wextra -g $(all_includes)
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noinst_LIBRARIES = libv27.a
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libv27_a_SOURCES = \
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scrambler.c \
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psk.c \
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modem.c
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@ -0,0 +1,89 @@
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/* V27 Modem
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*
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* (C) 2020 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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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 3 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 <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include "../libdebug/debug.h"
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#include "../libsample/sample.h"
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#include "modem.h"
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static int psk_send_bit(void *inst)
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{
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v27modem_t *modem = (v27modem_t *)inst;
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uint8_t bit;
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bit = modem->send_bit(modem->inst);
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bit = v27_scrambler_bit(&modem->scrambler, bit);
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return bit;
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}
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static void psk_receive_bit(void *inst, int bit)
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{
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v27modem_t *modem = (v27modem_t *)inst;
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bit = v27_scrambler_bit(&modem->descrambler, bit);
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modem->receive_bit(modem->inst, bit);
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}
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/* init psk */
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int v27_modem_init(v27modem_t *modem, void *inst, int (*send_bit)(void *inst), void (*receive_bit)(void *inst, int bit), int samplerate, int bis)
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{
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int rc = 0;
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memset(modem, 0, sizeof(*modem));
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modem->send_bit = send_bit;
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modem->receive_bit = receive_bit;
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modem->inst = inst;
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/* V.27bis/ter with 4800 bps */
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rc = psk_mod_init(&modem->psk_mod, modem, psk_send_bit, samplerate, 1600.0);
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if (rc)
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goto error;
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rc = psk_demod_init(&modem->psk_demod, modem, psk_receive_bit, samplerate, 1600.0);
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if (rc)
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goto error;
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v27_scrambler_init(&modem->scrambler, bis, 0);
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v27_scrambler_init(&modem->descrambler, bis, 1);
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return 0;
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error:
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v27_modem_exit(modem);
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return rc;
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}
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void v27_modem_exit(v27modem_t *modem)
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{
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psk_mod_exit(&modem->psk_mod);
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psk_demod_exit(&modem->psk_demod);
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}
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void v27_modem_send(v27modem_t *modem, sample_t *sample, int length)
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{
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psk_mod(&modem->psk_mod, sample, length);
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}
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void v27_modem_receive(v27modem_t *modem, sample_t *sample, int length)
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{
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psk_demod(&modem->psk_demod, sample, length);
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}
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@ -0,0 +1,18 @@
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#include "psk.h"
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#include "scrambler.h"
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typedef struct v27modem {
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int (*send_bit)(void *inst);
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void (*receive_bit)(void *inst, int bit);
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void *inst;
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v27scrambler_t scrambler, descrambler;
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psk_mod_t psk_mod;
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psk_demod_t psk_demod;
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} v27modem_t;
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int v27_modem_init(v27modem_t *modem, void *inst, int (*send_bit)(void *inst), void (*receive_bit)(void *inst, int bit), int samplerate, int bis);
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void v27_modem_exit(v27modem_t *modem);
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void v27_modem_send(v27modem_t *modem, sample_t *sample, int length);
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void v27_modem_receive(v27modem_t *modem, sample_t *sample, int length);
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@ -0,0 +1,459 @@
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/* Jolly's Version of PSK
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*
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* (C) 2020 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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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 3 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 <stdio.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <math.h>
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#include "../libdebug/debug.h"
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#include "../libsample/sample.h"
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#include "psk.h"
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/* bits to phase change */
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double phase_change8[8] = {
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2.0 * M_PI * 1.0 / 8.0,
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2.0 * M_PI * 0.0 / 8.0,
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2.0 * M_PI * 2.0 / 8.0,
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2.0 * M_PI * 3.0 / 8.0,
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2.0 * M_PI * 6.0 / 8.0,
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2.0 * M_PI * 7.0 / 8.0,
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2.0 * M_PI * 5.0 / 8.0,
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2.0 * M_PI * 4.0 / 8.0,
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};
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/* phase change to bits */
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uint8_t phase2bits[8] = { 1, 0, 2, 3, 7, 6, 4, 5 };
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/* debug decoder */
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//#define DEBUG_DECODER
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/* use SIT original encoder */
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//#define SIT_ENCODER
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/* may be different for testing purpose */
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#define TX_CARRIER 1800.0
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#define RX_CARRIER 1800.0
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#ifdef SIT_ENCODER
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static int8_t symbols_int[8][30] = {
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{ 0xff, 0xfd, 0x00, 0x02, 0xfe, 0x02, 0x0d, 0x05, 0xf9, 0x05, 0x02, 0xd2, 0xc9, 0x23, 0x64, 0x23,
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0xc9, 0xd2, 0x02, 0x05, 0xf9, 0x05, 0x0d, 0x02, 0xfe, 0x02, 0x00, 0xfd, 0xff, 0x00 },
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{ 0xfe, 0xff, 0x03, 0x02, 0xff, 0x07, 0x0a, 0xfa, 0xf7, 0x03, 0xef, 0xd0, 0xfe, 0x56, 0x47, 0xdb,
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0xb4, 0xef, 0x14, 0x03, 0xff, 0x0e, 0x09, 0xfc, 0xfe, 0x01, 0xfd, 0xfd, 0x00, 0x00 },
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{ 0xff, 0x01, 0x04, 0x01, 0x01, 0x08, 0x00, 0xf2, 0xfa, 0x00, 0xe6, 0xea, 0x34, 0x57, 0x00, 0xa9,
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0xcc, 0x16, 0x1a, 0x00, 0x06, 0x0e, 0x00, 0xf8, 0xff, 0xff, 0xfc, 0xff, 0x01, 0x00 },
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{ 0x00, 0x03, 0x03, 0xff, 0x02, 0x04, 0xf7, 0xf2, 0x01, 0xfd, 0xec, 0x11, 0x4c, 0x25, 0xb9, 0xaa,
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0x02, 0x30, 0x11, 0xfd, 0x09, 0x06, 0xf6, 0xf9, 0x01, 0xfe, 0xfd, 0x01, 0x02, 0x00 },
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{ 0x01, 0x03, 0x00, 0xfe, 0x02, 0xfe, 0xf3, 0xfb, 0x07, 0xfb, 0xfe, 0x2e, 0x37, 0xdd, 0x9c, 0xdd,
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0x37, 0x2e, 0xfe, 0xfb, 0x07, 0xfb, 0xf3, 0xfe, 0x02, 0xfe, 0x00, 0x03, 0x01, 0x00 },
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{ 0x02, 0x01, 0xfd, 0xfe, 0x01, 0xf9, 0xf6, 0x06, 0x09, 0xfd, 0x11, 0x30, 0x02, 0xaa, 0xb9, 0x25,
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0x4c, 0x11, 0xec, 0xfd, 0x01, 0xf2, 0xf7, 0x04, 0x02, 0xff, 0x03, 0x03, 0x00, 0x00 },
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{ 0x01, 0xff, 0xfc, 0xff, 0xff, 0xf8, 0x00, 0x0e, 0x06, 0x00, 0x1a, 0x16, 0xcc, 0xa9, 0x00, 0x57,
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0x34, 0xea, 0xe6, 0x00, 0xfa, 0xf2, 0x00, 0x08, 0x01, 0x01, 0x04, 0x01, 0xff, 0x00 },
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{ 0x00, 0xfd, 0xfd, 0x01, 0xfe, 0xfc, 0x09, 0x0e, 0xff, 0x03, 0x14, 0xef, 0xb4, 0xdb, 0x47, 0x56,
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0xfe, 0xd0, 0xef, 0x03, 0xf7, 0xfa, 0x0a, 0x07, 0xff, 0x02, 0x03, 0xff, 0xfe, 0x00 },
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};
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static sample_t symbols[8][150];
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/* indexes are rotated by 45 degrees, because the phase change during one symbol is 360+45 degrees */
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static int bits2index[8] = { 2, 1, 3, 4, 7, 0, 6, 5 };
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#endif
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/* init psk */
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int psk_mod_init(psk_mod_t *psk, void *inst, int (*send_bit)(void *inst), int samplerate, double symbolrate)
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{
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double cutoff, transitionband;
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memset(psk, 0, sizeof(*psk));
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psk->send_bit = send_bit;
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psk->inst = inst;
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#ifdef SIT_ENCODER
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int i, j, s;
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sample_t spl;
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if (samplerate != 48000) {
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PDEBUG(DDSP, DEBUG_NOTICE, "Sampling rate for PSK encoder must be exactly 48000 Hz!\n");
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return -EINVAL;
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}
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if (symbolrate != 1600) {
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PDEBUG(DDSP, DEBUG_NOTICE, "Symbol rate for PSK encoder must be exactly 1600 Hz!\n");
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return -EINVAL;
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}
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cutoff = 3300.0;
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transitionband = 200;
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psk->lp[0] = fir_lowpass_init((double)samplerate, cutoff, transitionband);
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PDEBUG(DDSP, DEBUG_DEBUG, "Cut off frequency is at %.1f Hz and %.1f Hz.\n", TX_CARRIER + cutoff, TX_CARRIER - cutoff);
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/* interpolate symbol table from 9600 Hz to 48000 Hz */
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for (i = 0; i < 8; i++) {
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for (j = 0, s = 0; j < 30; j++) {
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spl = (double)symbols_int[i][j] / 128.0;
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symbols[i][s++] = spl;
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symbols[i][s++] = spl;
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symbols[i][s++] = spl;
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symbols[i][s++] = spl;
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symbols[i][s++] = spl;
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}
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}
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#else
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if (samplerate < 48000) {
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PDEBUG(DDSP, DEBUG_NOTICE, "Sampling rate for PSK encoder must be 48000 Hz minimum!\n");
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return -EINVAL;
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}
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/* fixme: make correct filter */
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cutoff = RX_CARRIER - 100;
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transitionband = 200;
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psk->lp[0] = fir_lowpass_init((double)samplerate, cutoff, transitionband);
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psk->lp[1] = fir_lowpass_init((double)samplerate, cutoff, transitionband);
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PDEBUG(DDSP, DEBUG_DEBUG, "Cut off frequency is at %.1f Hz and %.1f Hz.\n", TX_CARRIER + cutoff, TX_CARRIER - cutoff);
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psk->symbols_per_sample = symbolrate / (double)samplerate;
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PDEBUG(DDSP, DEBUG_DEBUG, "Symbol duration of %.4f symbols per sample @ %d.\n", psk->symbols_per_sample, samplerate);
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psk->carrier_phaseshift = 2.0 * M_PI * TX_CARRIER / (double)samplerate;
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PDEBUG(DDSP, DEBUG_DEBUG, "Carrier phase shift of %.4f per sample @ %d.\n", psk->carrier_phaseshift, samplerate);
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#endif
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return 0;
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}
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void psk_mod_exit(psk_mod_t *psk)
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{
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if (psk->lp[0]) {
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fir_exit(psk->lp[0]);
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psk->lp[0] = NULL;
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}
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if (psk->lp[1]) {
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fir_exit(psk->lp[1]);
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psk->lp[1] = NULL;
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}
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}
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void psk_mod(psk_mod_t *psk, sample_t *sample, int length)
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{
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uint8_t bits;
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int s;
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#ifdef SIT_ENCODER
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int index;
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for (s = 0; s < length; s++) {
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if (psk->spl_count == 0) {
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bits = (psk->send_bit(psk->inst) & 1) << 2;
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bits |= (psk->send_bit(psk->inst) & 1) << 1;
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bits |= (psk->send_bit(psk->inst) & 1);
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#ifdef DEBUG_DECODER
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static int nextbit = 0;
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if (++nextbit == 8)
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nextbit = 0;
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bits = nextbit;
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#endif
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index = psk->sym_list[psk->sym_count];
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psk->sym_count = (psk->sym_count + 1) % 5;
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psk->sym_list[psk->sym_count] = (index + bits2index[bits]) & 7;
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}
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sample[s] = symbols[psk->sym_list[psk->sym_count]][psk->spl_count];
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sample[s] += symbols[psk->sym_list[(psk->sym_count + 4) % 5]][30 + psk->spl_count];
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sample[s] += symbols[psk->sym_list[(psk->sym_count + 3) % 5]][60 + psk->spl_count];
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sample[s] += symbols[psk->sym_list[(psk->sym_count + 2) % 5]][90 + psk->spl_count];
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sample[s] += symbols[psk->sym_list[(psk->sym_count + 1) % 5]][120 + psk->spl_count];
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if (++psk->spl_count == 30)
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psk->spl_count = 0;
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}
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fir_process(psk->lp[0], sample, length);
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#else
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sample_t I[length], Q[length];
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/* count symbol and get new bits for next symbol */
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for (s = 0; s < length; s++) {
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psk->symbol_pos += psk->symbols_per_sample;
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if (psk->symbol_pos >= 1.0) {
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psk->symbol_pos -= 1.0;
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/* get tree bits */
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bits = (psk->send_bit(psk->inst) & 1) << 2;
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bits |= (psk->send_bit(psk->inst) & 1) << 1;
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bits |= (psk->send_bit(psk->inst) & 1);
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#ifdef DEBUG_DECODER
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static int nextbit = 0;
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if (++nextbit == 8)
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nextbit = 0;
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bits = nextbit;
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#endif
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/* change phase_shift */
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psk->phase_shift += phase_change8[bits];
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if (psk->phase_shift > M_PI)
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psk->phase_shift -= 2.0 * M_PI;
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}
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I[s] = cos(psk->phase_shift);
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Q[s] = sin(psk->phase_shift);
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}
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/* filter phase_shift to limit bandwidth */
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fir_process(psk->lp[0], I, length);
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fir_process(psk->lp[1], Q, length);
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/* modulate with carrier frequency */
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for (s = 0; s < length; s++) {
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/* compensate overshooting of filter */
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*sample++ = (I[s] * cos(psk->carrier_phase) - Q[s] * sin(psk->carrier_phase)) * 0.7;
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psk->carrier_phase += psk->carrier_phaseshift;
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if (psk->carrier_phase >= 2.0 * M_PI)
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psk->carrier_phase -= 2.0 * M_PI;
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}
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#endif
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}
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int psk_demod_init(psk_demod_t *psk, void *inst, void (*receive_bit)(void *inst, int bit), int samplerate, double symbolrate)
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{
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double cutoff, transitionband;
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if (samplerate < 48000) {
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PDEBUG(DDSP, DEBUG_NOTICE, "Sampling rate for PSK decoder must be 48000 Hz minimum!\n");
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return -EINVAL;
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}
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memset(psk, 0, sizeof(*psk));
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psk->receive_bit = receive_bit;
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psk->inst = inst;
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/* fixme: make correct filter */
|
||||
// cutoff = symbolrate / 2.0 * 1.5;
|
||||
cutoff = RX_CARRIER - 100;
|
||||
transitionband = 200;
|
||||
psk->lp[0] = fir_lowpass_init((double)samplerate, cutoff, transitionband);
|
||||
psk->lp[1] = fir_lowpass_init((double)samplerate, cutoff, transitionband);
|
||||
iir_lowpass_init(&psk->lp_error[0], 50.0, samplerate, 2);
|
||||
iir_lowpass_init(&psk->lp_error[1], 50.0, samplerate, 2);
|
||||
iir_bandpass_init(&psk->lp_clock, symbolrate, samplerate, 40);
|
||||
psk->sample_delay = (int)floor((double)samplerate / symbolrate * 0.25); /* percent of sine duration behind zero crossing */
|
||||
PDEBUG(DDSP, DEBUG_DEBUG, "Cut off frequency is at %.1f Hz and %.1f Hz.\n", RX_CARRIER + cutoff, RX_CARRIER - cutoff);
|
||||
|
||||
psk->carrier_phaseshift = 2.0 * M_PI * -RX_CARRIER / (double)samplerate;
|
||||
PDEBUG(DDSP, DEBUG_DEBUG, "Carrier phase shift of %.4f per sample @ %d.\n", psk->carrier_phaseshift, samplerate);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
void psk_demod_exit(psk_demod_t *psk)
|
||||
{
|
||||
if (psk->lp[0]) {
|
||||
fir_exit(psk->lp[0]);
|
||||
psk->lp[0] = NULL;
|
||||
}
|
||||
if (psk->lp[1]) {
|
||||
fir_exit(psk->lp[1]);
|
||||
psk->lp[1] = NULL;
|
||||
}
|
||||
}
|
||||
|
||||
#ifdef DEBUG_DECODER
|
||||
static void debug_phase(double phase, double amplitude, double error, double amplitude2)
|
||||
{
|
||||
int x, y, xx = 100, yy = 50;
|
||||
char buffer[yy][xx + 1];
|
||||
double p;
|
||||
int i;
|
||||
|
||||
if (amplitude > 1.0)
|
||||
amplitude = 1.0;
|
||||
if (amplitude < -0.0)
|
||||
amplitude = -0.0;
|
||||
if (amplitude2 > 0.5)
|
||||
amplitude2 = 0.5;
|
||||
if (amplitude2 < -0.5)
|
||||
amplitude2 = -0.5;
|
||||
amplitude2 += 0.5;
|
||||
|
||||
/* clear (EOL) and fill spaces with border */
|
||||
memset(buffer, '\0', sizeof(buffer));
|
||||
memset(buffer[0], '#', xx);
|
||||
for (y = 1; y < yy - 1; y++) {
|
||||
memset(buffer[y], ' ', xx);
|
||||
buffer[y][0] = '|';
|
||||
buffer[y][xx - 1] = '|';
|
||||
}
|
||||
memset(buffer[yy - 1], '-', xx);
|
||||
buffer[0][0] = '+';
|
||||
buffer[0][xx - 1] = '+';
|
||||
buffer[yy - 1][0] = '+';
|
||||
buffer[yy - 1][xx - 1] = '+';
|
||||
|
||||
/* plot target angles on buffer */
|
||||
for (i = 0, p = 0.0; i < 8; i++, p = p + M_PI / 4.0) {
|
||||
y = -(sin(p + error) * (double)yy / 1.1) + (double)yy;
|
||||
x = (cos(p + error) * (double)xx / 2.2) + (double)xx / 2.0;
|
||||
buffer[y >> 1][x] = '0' + i;
|
||||
}
|
||||
|
||||
/* plot angle on buffer */
|
||||
y = -(amplitude * 1.1 * sin(phase) * (double)yy / 1.1) + (double)yy;
|
||||
x = (amplitude * 1.1 * cos(phase) * (double)xx / 2.2) + (double)xx / 2.0;
|
||||
if ((y & 1))
|
||||
buffer[y >> 1][x] = '.';
|
||||
else
|
||||
buffer[y >> 1][x] = '\'';
|
||||
|
||||
/* plot amplitude on buffer */
|
||||
y = -(amplitude * (double)yy * 2.0 / 1.1) + (double)yy * 2.0 / 1.1;
|
||||
if ((y & 1))
|
||||
buffer[y >> 1][1] = '.';
|
||||
else
|
||||
buffer[y >> 1][1] = '\'';
|
||||
y = -(amplitude2 * (double)yy * 2.0 / 1.1) + (double)yy * 2.0 / 1.1;
|
||||
if ((y & 1))
|
||||
buffer[y >> 1][2] = '.';
|
||||
else
|
||||
buffer[y >> 1][2] = '\'';
|
||||
|
||||
/* display on screen */
|
||||
for (y = 0; y < yy; y++)
|
||||
printf("%s\n", buffer[y]);
|
||||
}
|
||||
#endif
|
||||
|
||||
void psk_demod(psk_demod_t *psk, sample_t *sample, int length)
|
||||
{
|
||||
sample_t I[length], Q[length], i;
|
||||
sample_t Ip[length], Qp[length];
|
||||
double phases[length];
|
||||
sample_t amplitudes[length], amplitudes2[length];
|
||||
double phaseshift, phase, phase_error, angle_error;
|
||||
uint16_t phase_error_int, offset;
|
||||
int s, ss;
|
||||
uint8_t sector, rotation, bits;
|
||||
|
||||
/* demodulate phase from carrier */
|
||||
phaseshift = psk->carrier_phaseshift;
|
||||
phase = psk->carrier_phase;
|
||||
for (s = 0, ss = 0; s < length; s++) {
|
||||
phase += phaseshift;
|
||||
i = sample[ss++];
|
||||
if (phase < 0)
|
||||
phase += 2.0 * M_PI;
|
||||
else if (phase >= 2.0 * M_PI)
|
||||
phase -= 2.0 * M_PI;
|
||||
I[s] = i * cos(phase);
|
||||
Q[s] = i * sin(phase);
|
||||
}
|
||||
psk->carrier_phase = phase;
|
||||
fir_process(psk->lp[0], I, length);
|
||||
fir_process(psk->lp[1], Q, length);
|
||||
|
||||
/* get phase error */
|
||||
for (s = 0, ss = 0; s < length; s++) {
|
||||
phases[s] = atan2(Q[s], I[s]);
|
||||
amplitudes[s] = sqrt(Q[s] * Q[s] + I[s] * I[s]) * 2.0;
|
||||
amplitudes2[s] = amplitudes[s];
|
||||
Ip[s] = amplitudes[s] * cos(phases[s] * 8.0) * 2.0;
|
||||
Qp[s] = amplitudes[s] * sin(phases[s] * 8.0) * 2.0;
|
||||
}
|
||||
iir_process(&psk->lp_error[0], Ip, length);
|
||||
iir_process(&psk->lp_error[1], Qp, length);
|
||||
|
||||
/* filter amplitude to get symbol clock */
|
||||
/* NOTE: the filter biases the amplitude, so that we have positive and negative peaks.
|
||||
positive peak is the sample point */
|
||||
iir_process(&psk->lp_clock, amplitudes2, length);
|
||||
|
||||
for (s = 0; s < length; s++) {
|
||||
/* calculate change of phase error angle within one sample */
|
||||
phase_error_int = (int)floor(atan2(Qp[s], Ip[s]) / (2.0 * M_PI) * 65536.0);
|
||||
offset = phase_error_int - psk->last_phase_error;
|
||||
psk->last_phase_error = phase_error_int;
|
||||
|
||||
/* apply change to current phase error value */
|
||||
psk->phase_error += (int16_t)offset;
|
||||
if (psk->phase_error >= 65536 * 8)
|
||||
psk->phase_error -= 65536 * 8;
|
||||
if (psk->phase_error < 0)
|
||||
psk->phase_error += 65536 * 8;
|
||||
|
||||
phase_error = (double)psk->phase_error / 65536.0 * (2.0 * M_PI) / 8.0;
|
||||
|
||||
/* if we have reached a zero crossing of the amplitude signal, wait for sample point */
|
||||
if (psk->sample_timer && --psk->sample_timer == 0) {
|
||||
/* sample point reached */
|
||||
phase = fmod(phases[s] - phase_error + 4.0 * M_PI, 2.0 * M_PI);
|
||||
if (phase < 2.0 * M_PI / 16.0 * 1.0)
|
||||
sector = 0;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 3.0)
|
||||
sector = 1;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 5.0)
|
||||
sector = 2;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 7.0)
|
||||
sector = 3;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 9.0)
|
||||
sector = 4;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 11.0)
|
||||
sector = 5;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 13.0)
|
||||
sector = 6;
|
||||
else if (phase < 2.0 * M_PI / 16.0 * 15.0)
|
||||
sector = 7;
|
||||
else
|
||||
sector = 0;
|
||||
angle_error = fmod(phase / 2.0 / M_PI * 8.0, 1.0);
|
||||
if (angle_error > 0.5)
|
||||
angle_error -= 1.0;
|
||||
|
||||
rotation = (sector - psk->last_sector) & 7; // might be negative, so we use AND!
|
||||
bits = phase2bits[rotation];
|
||||
#ifdef DEBUG_DECODER
|
||||
printf("sector=%d last_sector=%d rotation=%d bits=%d angle_error=%.2f\n", sector, psk->last_sector, rotation, bits, angle_error);
|
||||
#endif
|
||||
psk->last_sector = sector;
|
||||
/* report bits */
|
||||
#ifndef DEBUG_DECODER
|
||||
psk->receive_bit(psk->inst, bits >> 2);
|
||||
psk->receive_bit(psk->inst, (bits >> 1) & 1);
|
||||
psk->receive_bit(psk->inst, bits & 1);
|
||||
#endif
|
||||
}
|
||||
if (psk->last_amplitude <= 0.0 && amplitudes2[s] > 0.0)
|
||||
psk->sample_timer = psk->sample_delay;
|
||||
psk->last_amplitude = amplitudes2[s];
|
||||
|
||||
#ifdef DEBUG_DECODER
|
||||
static int when = 0;
|
||||
if (++when > 10000) {
|
||||
printf("\0337\033[H");
|
||||
/* display amplitude between 0.0 and 1.0, aplitude2 between -0.5 and 0.5 */
|
||||
debug_phase(phases[s], amplitudes[s], phase_error, amplitudes2[s]);
|
||||
printf("phase2 = %.4f offset = %d, error = %d (error & 0xffff = %d)\n", phase_error, offset, psk->phase_error, psk->phase_error & 0xffff);
|
||||
printf("\033[0;39m\0338"); fflush(stdout);
|
||||
usleep(50000);
|
||||
}
|
||||
#endif
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,48 @@
|
|||
#include "../libfilter/iir_filter.h"
|
||||
#include "../libfilter/fir_filter.h"
|
||||
|
||||
typedef struct psk_mod {
|
||||
int (*send_bit)(void *inst);
|
||||
void *inst;
|
||||
|
||||
double symbol_pos; /* current position in symbol */
|
||||
double symbols_per_sample; /* change of position per sample */
|
||||
double phase_shift; /* carrier phase shift */
|
||||
double carrier_phase; /* current carrier phase */
|
||||
double carrier_phaseshift; /* shift of phase per sample */
|
||||
|
||||
fir_filter_t *lp[2]; /* filter for limiting spectrum */
|
||||
|
||||
int spl_count; /* SIT: counter for 30 samples (symbol duration) */
|
||||
int sym_list[5]; /* SIT: list of 5 symbols */
|
||||
int sym_count; /* SIT: current list index */
|
||||
} psk_mod_t;
|
||||
|
||||
typedef struct psk_demod {
|
||||
void (*receive_bit)(void *inst, int bit);
|
||||
void *inst;
|
||||
|
||||
double carrier_phase; /* current carrier phase */
|
||||
double carrier_phaseshift; /* shift of phase per sample */
|
||||
|
||||
fir_filter_t *lp[2]; /* filter for limiting spectrum */
|
||||
iir_filter_t lp_error[2]; /* filter for phase correction */
|
||||
iir_filter_t lp_clock; /* filter for symbol clock */
|
||||
|
||||
uint16_t last_phase_error; /* error phase of last sample */
|
||||
int32_t phase_error; /* current phase error */
|
||||
|
||||
sample_t last_amplitude; /* clock amplitude of last sample */
|
||||
int sample_delay; /* delay of quarter symbol length in samples */
|
||||
int sample_timer; /* counter to wait for the symbol's sample point */
|
||||
|
||||
uint8_t last_sector; /* sector of last symbol */
|
||||
} psk_demod_t;
|
||||
|
||||
int psk_mod_init(psk_mod_t *psk, void *inst, int (*send_bit)(void *inst), int samplerate, double symbolrate);
|
||||
void psk_mod_exit(psk_mod_t *psk);
|
||||
void psk_mod(psk_mod_t *psk, sample_t *sample, int length);
|
||||
int psk_demod_init(psk_demod_t *psk, void *inst, void (*receive_bit)(void *inst, int bit), int samplerate, double symbolrate);
|
||||
void psk_demod_exit(psk_demod_t *psk);
|
||||
void psk_demod(psk_demod_t *psk, sample_t *sample, int length);
|
||||
|
|
@ -0,0 +1,163 @@
|
|||
/* V.27(bis) Scrambler / Descrambler
|
||||
*
|
||||
* (C) 2020 by Andreas Eversberg <jolly@eversberg.eu>
|
||||
* All Rights Reserved
|
||||
*
|
||||
* 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 3 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/>.
|
||||
*/
|
||||
|
||||
/* Based on orignal Scrambler code from SIT-Rom:
|
||||
|
||||
r6 already has input bit at position 0.
|
||||
r6 (low) and r7 (high) are the shift register.
|
||||
The register is shifed during process, so that compare at 00BE and
|
||||
00C5 refers to the already shifted register and not to the original
|
||||
position.
|
||||
|
||||
00A4 L00A4:
|
||||
00A4 : FE mov a,r6
|
||||
00A5 : ED AF djnz r5,L00AF
|
||||
00A7 : D3 01 xrl a,#001H
|
||||
00A9 : BD 22 mov r5,#022H
|
||||
00AB L00AB:
|
||||
00AB : D2 B3 jb6 L00B3
|
||||
00AD : 04 B5 jmp L00B5
|
||||
;
|
||||
00AF L00AF:
|
||||
00AF : 00 nop
|
||||
00B0 : 00 nop
|
||||
00B1 : 04 AB jmp L00AB
|
||||
;
|
||||
00B3 L00B3:
|
||||
00B3 : D3 01 xrl a,#001H
|
||||
00B5 L00B5:
|
||||
00B5 : F2 B9 jb7 L00B9
|
||||
00B7 : 04 BB jmp L00BB
|
||||
;
|
||||
00B9 L00B9:
|
||||
00B9 : D3 01 xrl a,#001H
|
||||
00BB L00BB:
|
||||
00BB : 97 clr c
|
||||
00BC : F7 rlc a
|
||||
00BD : AE mov r6,a
|
||||
00BE : 32 CB jb1 L00CB
|
||||
00C0 : FF mov a,r7
|
||||
00C1 : F7 rlc a
|
||||
00C2 : AF mov r7,a
|
||||
00C3 : 37 cpl a
|
||||
00C4 : 00 nop
|
||||
00C5 L00C5:
|
||||
00C5 : 53 26 anl a,#026H
|
||||
00C7 : C6 D0 jz L00D0
|
||||
00C9 : 04 D2 jmp L00D2
|
||||
;
|
||||
00CB L00CB:
|
||||
00CB : FF mov a,r7
|
||||
00CC : F7 rlc a
|
||||
00CD : AF mov r7,a
|
||||
00CE : 04 C5 jmp L00C5
|
||||
;
|
||||
00D0 00D0:
|
||||
00D0 : BD 22 mov r5,#022H
|
||||
00D2 00D2:
|
||||
00D2 : 83 ret
|
||||
|
||||
*/
|
||||
|
||||
#include <stdio.h>
|
||||
#include <stdint.h>
|
||||
#include <string.h>
|
||||
#include "scrambler.h"
|
||||
|
||||
#define GUARD_COUNT 34
|
||||
|
||||
/* init scrambler */
|
||||
void v27_scrambler_init(v27scrambler_t *scram, int bis, int descramble)
|
||||
{
|
||||
memset(scram, 0, sizeof(*scram));
|
||||
|
||||
scram->descramble = descramble;
|
||||
|
||||
/* set bits 9 and 12 (and 8 for V.27bis) */
|
||||
if (bis)
|
||||
scram->resetmask = 0x1300;
|
||||
else
|
||||
scram->resetmask = 0x1200;
|
||||
|
||||
/* guard counter */
|
||||
scram->counter = GUARD_COUNT;
|
||||
}
|
||||
|
||||
/* scramble/descramble one bit */
|
||||
uint8_t v27_scrambler_bit(v27scrambler_t *scram, uint8_t in)
|
||||
{
|
||||
uint8_t bit0 = in & 1;
|
||||
uint16_t shift = scram->shift;
|
||||
|
||||
|
||||
/* the descrambler stores the input bit */
|
||||
if (scram->descramble) {
|
||||
/* put bit 0 into shift register and shift */
|
||||
shift |= bit0;
|
||||
scram->shift = shift << 1;
|
||||
}
|
||||
|
||||
/* process guaard counter */
|
||||
if (--scram->counter == 0) {
|
||||
/* restart counter */
|
||||
scram->counter = GUARD_COUNT;
|
||||
/* invert this time */
|
||||
bit0 ^= 1;
|
||||
}
|
||||
|
||||
/* xor bit 0 with bits 6 and 7: polynome 1 + x^-6 + x^-7 */
|
||||
bit0 ^= ((shift >> 6) & 1);
|
||||
bit0 ^= ((shift >> 7) & 1);
|
||||
|
||||
/* the scrambler stores the output bit */
|
||||
if (!scram->descramble) {
|
||||
/* put bit 0 into shift register and shift */
|
||||
shift |= bit0;
|
||||
scram->shift = shift << 1;
|
||||
}
|
||||
|
||||
/* check if bits (8),9,12 are repitions of bit 0 in shift register (prior shift) */
|
||||
if (!(shift & 1))
|
||||
shift ^= ~0;
|
||||
if (!(shift & scram->resetmask)) {
|
||||
/* any repetition is not true, reset counter */
|
||||
scram->counter = GUARD_COUNT;
|
||||
}
|
||||
|
||||
return bit0;
|
||||
}
|
||||
|
||||
/* scramble/descramble block of bytes (LSB first) */
|
||||
void v27_scrambler_block(v27scrambler_t *scram, uint8_t *data, int len)
|
||||
{
|
||||
int i, j;
|
||||
uint8_t in, out = 0;
|
||||
|
||||
for (i = 0; i < len; i++) {
|
||||
in = data[i];
|
||||
for (j = 0; j < 8; j++) {
|
||||
out >>= 1;
|
||||
// Note: 'in' will be masked to bit 0 only
|
||||
out |= v27_scrambler_bit(scram, in) << 7;
|
||||
in >>= 1;
|
||||
}
|
||||
data[i] = out;
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,13 @@
|
|||
|
||||
typedef struct v27scrambler {
|
||||
int descramble; /* set if we descramble */
|
||||
|
||||
uint16_t shift; /* shift register to hold 13 bits */
|
||||
int counter; /* counter to guard against repetitions */
|
||||
uint16_t resetmask; /* bit mask for repition check */
|
||||
} v27scrambler_t;
|
||||
|
||||
void v27_scrambler_init(v27scrambler_t *scram, int bis, int descramble);
|
||||
uint8_t v27_scrambler_bit(v27scrambler_t *scram, uint8_t in);
|
||||
void v27_scrambler_block(v27scrambler_t *scram, uint8_t *data, int len);
|
||||
|
|
@ -9,7 +9,8 @@ noinst_PROGRAMS = \
|
|||
test_dms \
|
||||
test_sms \
|
||||
test_performance \
|
||||
test_hagelbarger
|
||||
test_hagelbarger \
|
||||
test_v27scrambler
|
||||
|
||||
test_filter_SOURCES = test_filter.c dummy.c
|
||||
|
||||
|
@ -136,3 +137,10 @@ test_hagelbarger_LDADD = \
|
|||
$(top_builddir)/src/libhagelbarger/libhagelbarger.a \
|
||||
-lm
|
||||
|
||||
test_v27scrambler_SOURCES = dummy.c test_v27scrambler.c
|
||||
|
||||
test_v27scrambler_LDADD = \
|
||||
$(COMMON_LA) \
|
||||
$(top_builddir)/src/libv27/libv27.a \
|
||||
-lm
|
||||
|
||||
|
|
|
@ -0,0 +1,133 @@
|
|||
#include "stdio.h"
|
||||
#include "stdint.h"
|
||||
#include "string.h"
|
||||
#include "../libv27/scrambler.h"
|
||||
|
||||
static int show_bin(uint8_t *data1, uint8_t *data2, int len)
|
||||
{
|
||||
int i, j, error = 0;;
|
||||
uint8_t bit1, bit2;
|
||||
|
||||
for (i = 0; i < len; i++) {
|
||||
printf(".");
|
||||
for (j = 0; j < 8; j++) {
|
||||
bit1 = (data1[i] >> j) & 1;
|
||||
bit2 = (data2[i] >> j) & 1;
|
||||
if (bit1 == bit2)
|
||||
printf("%d", bit1);
|
||||
else {
|
||||
printf("X");
|
||||
error++;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
printf("\n");
|
||||
|
||||
return error;
|
||||
}
|
||||
|
||||
static int check_repetition(uint8_t *data, int len, int repeat, int start)
|
||||
{
|
||||
int i;
|
||||
uint8_t b1, b2;
|
||||
|
||||
for (i = start; i < (len * 8 - repeat); i++) {
|
||||
b1 = (data[i >> 3] >> (i & 7)) & 1;
|
||||
b2 = (data[(i+repeat) >> 3] >> ((i+repeat) & 7)) & 1;
|
||||
if (b1 != b2)
|
||||
return i - start + repeat;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
int main(void)
|
||||
{
|
||||
v27scrambler_t scram, descram;
|
||||
|
||||
char message[] = "Jolly Roger~~~~";
|
||||
int len = strlen(message);
|
||||
uint8_t data[len];
|
||||
int ret;
|
||||
|
||||
printf("Message: %s\n", message);
|
||||
|
||||
memcpy(data, message, len);
|
||||
show_bin(data, (uint8_t *)message, len);
|
||||
|
||||
v27_scrambler_init(&scram, 1, 0);
|
||||
v27_scrambler_block(&scram, data, len);
|
||||
|
||||
printf("Scrambled:\n");
|
||||
show_bin(data, data, len);
|
||||
|
||||
v27_scrambler_init(&descram, 1, 1);
|
||||
v27_scrambler_block(&descram, data, len);
|
||||
|
||||
printf("Descramble without corruption?\n");
|
||||
|
||||
ret = show_bin(data, (uint8_t *)message, len);
|
||||
if (ret) {
|
||||
printf("Descrambling failed!\n");
|
||||
return 1;
|
||||
}
|
||||
printf("Yes!\n");
|
||||
|
||||
printf("\n");
|
||||
|
||||
v27_scrambler_init(&scram, 1, 0);
|
||||
v27_scrambler_block(&scram, data, len);
|
||||
|
||||
data[0] = 'B';
|
||||
data[1] = 'U';
|
||||
data[2] = 'G';
|
||||
|
||||
v27_scrambler_init(&descram, 1, 1);
|
||||
v27_scrambler_block(&descram, data, len);
|
||||
|
||||
printf("Descramble with 3 bytes corruption: (should fix itself after 4 bytes)\n");
|
||||
|
||||
show_bin(data, (uint8_t *)message, len);
|
||||
|
||||
printf("\n");
|
||||
|
||||
printf("Descramble a scrambled sequence of 8 bit repetitions with V.27: 01111110\n");
|
||||
|
||||
memset(data, 0x7e, len);
|
||||
|
||||
v27_scrambler_init(&descram, 0, 1);
|
||||
v27_scrambler_block(&descram, data, len);
|
||||
|
||||
show_bin(data, (uint8_t *)data, len);
|
||||
|
||||
/* note at position 6 we have no more change towards 8 bit offset */
|
||||
ret = check_repetition(data, len, 8, 6);
|
||||
if (ret) {
|
||||
printf("Theres is a change of repetition after %d bits after start %d, please fix!\n", ret, 6);
|
||||
return 1;
|
||||
}
|
||||
printf("Repetition not detected, good!\n");
|
||||
|
||||
printf("\n");
|
||||
|
||||
printf("Descramble a scrambled sequence of 8 bit repetitions with V.27bis/ter: 01111110\n");
|
||||
|
||||
memset(data, 0x7e, len);
|
||||
|
||||
v27_scrambler_init(&descram, 1, 1);
|
||||
v27_scrambler_block(&descram, data, len);
|
||||
|
||||
show_bin(data, (uint8_t *)data, len);
|
||||
|
||||
/* note at position 6 we have no more change towards 8 bit offset */
|
||||
ret = check_repetition(data, len, 8, 6);
|
||||
if (ret != 34) {
|
||||
printf("Theres is NO change of repetition after 34 bits, but after %d bits, which should not happen!\n", ret);
|
||||
return 1;
|
||||
}
|
||||
printf("Repetition detected after %d bits from start %d, good!\n", ret, 6);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
Loading…
Reference in New Issue