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/* V27 Modem
*
* (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/>.
*/
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include "../libdebug/debug.h"
#include "../libsample/sample.h"
#include "modem.h"
static int psk_send_bit(void *inst)
{
v27modem_t *modem = (v27modem_t *)inst;
uint8_t bit;
bit = modem->send_bit(modem->inst);
bit = v27_scrambler_bit(&modem->scrambler, bit);
return bit;
}
static void psk_receive_bit(void *inst, int bit)
{
v27modem_t *modem = (v27modem_t *)inst;
bit = v27_scrambler_bit(&modem->descrambler, bit);
modem->receive_bit(modem->inst, bit);
}
/* init psk */
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)
{
int rc = 0;
memset(modem, 0, sizeof(*modem));
modem->send_bit = send_bit;
modem->receive_bit = receive_bit;
modem->inst = inst;
/* V.27bis/ter with 4800 bps */
rc = psk_mod_init(&modem->psk_mod, modem, psk_send_bit, samplerate, 1600.0);
if (rc)
goto error;
rc = psk_demod_init(&modem->psk_demod, modem, psk_receive_bit, samplerate, 1600.0);
if (rc)
goto error;
v27_scrambler_init(&modem->scrambler, bis, 0);
v27_scrambler_init(&modem->descrambler, bis, 1);
return 0;
error:
v27_modem_exit(modem);
return rc;
}
void v27_modem_exit(v27modem_t *modem)
{
psk_mod_exit(&modem->psk_mod);
psk_demod_exit(&modem->psk_demod);
}
void v27_modem_send(v27modem_t *modem, sample_t *sample, int length)
{
psk_mod(&modem->psk_mod, sample, length);
}
void v27_modem_receive(v27modem_t *modem, sample_t *sample, int length)
{
psk_demod(&modem->psk_demod, sample, length);
}
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