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jdsca tests

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This commit is contained in:
kuba
2026-07-11 22:07:33 +02:00
parent bcd9468770
commit 8a4cbb9b5f
3 changed files with 140 additions and 2 deletions
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lib/qpsk.c
+66
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@@ -0,0 +1,66 @@
#include "qpsk.h"
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define OQPSK_RRC_DELAY 6 // filter delay in symbols (liquid's "m" param)
static void oqpsk_next_dibit(OQPSKMod *m, float *i, float *q) {
uint8_t b0 = m->last_bits[0], b1 = m->last_bits[1], bit;
if (bit_ring_read1(m->bitring, &bit)) b0 = bit;
if (bit_ring_read1(m->bitring, &bit)) b1 = bit;
m->last_bits[0] = b0;
m->last_bits[1] = b1;
*i = b0 ? -1.0f : 1.0f;
*q = b1 ? -1.0f : 1.0f;
}
void oqpsk_init(OQPSKMod *m, float if_freq, float sample_rate, float symbol_rate, float alpha, bit_ring_t *bitring) {
memset(m, 0, sizeof(*m));
init_oscillator(&m->carrier, if_freq, sample_rate);
m->sps = (int)roundf(sample_rate / symbol_rate);
if (m->sps < 2) m->sps = 2;
if (m->sps % 2 != 0) m->sps += 1; // must be even for the half-symbol Q delay
m->fir_i = firfilt_rrrf_create_rnyquist(LIQUID_FIRFILT_RRC, m->sps, OQPSK_RRC_DELAY, alpha, 0.0f);
m->fir_q = firfilt_rrrf_create_rnyquist(LIQUID_FIRFILT_RRC, m->sps, OQPSK_RRC_DELAY, alpha, 0.0f);
m->q_delay_len = m->sps / 2;
m->q_delay = calloc(m->q_delay_len, sizeof(float));
m->q_delay_pos = 0;
m->symbol_clock = 0;
m->sym_i = m->sym_q = 1.0f;
m->bitring = bitring;
}
float oqpsk_process(OQPSKMod *m) {
float impulse_i = 0.0f, impulse_q = 0.0f;
if (m->symbol_clock == 0) {
oqpsk_next_dibit(m, &m->sym_i, &m->sym_q);
impulse_i = m->sym_i * (float)m->sps;
impulse_q = m->sym_q * (float)m->sps;
}
m->symbol_clock = (m->symbol_clock + 1) % m->sps;
float filt_i, filt_q_raw;
firfilt_rrrf_push(m->fir_i, impulse_i);
firfilt_rrrf_execute(m->fir_i, &filt_i);
firfilt_rrrf_push(m->fir_q, impulse_q);
firfilt_rrrf_execute(m->fir_q, &filt_q_raw);
float filt_q = m->q_delay[m->q_delay_pos];
m->q_delay[m->q_delay_pos] = filt_q_raw;
m->q_delay_pos = (m->q_delay_pos + 1) % m->q_delay_len;
float c = get_oscillator_cos_sample(&m->carrier);
float s = get_oscillator_sin_sample(&m->carrier);
return filt_i * c - filt_q * s;
}
void oqpsk_destroy(OQPSKMod *m) {
firfilt_rrrf_destroy(m->fir_i);
firfilt_rrrf_destroy(m->fir_q);
free(m->q_delay);
}
lib/qpsk.h
+22
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@@ -0,0 +1,22 @@
#pragma once
#include <liquid/liquid.h>
#include "oscillator.h"
#include "bit_ring.h"
typedef struct {
Oscillator carrier; // IF carrier (e.g. 3 kHz)
firfilt_rrrf fir_i, fir_q; // liquid RRC matched-filter shapers
float *q_delay;
int q_delay_len;
int q_delay_pos;
int sps; // samples per symbol
int symbol_clock;
float sym_i, sym_q;
bit_ring_t *bitring;
uint8_t last_bits[2]; // hold last symbol if bitring runs dry
} OQPSKMod;
void oqpsk_init(OQPSKMod *m, float if_freq, float sample_rate, float symbol_rate, float alpha, bit_ring_t *bitring);
float oqpsk_process(OQPSKMod *m);
void oqpsk_destroy(OQPSKMod *m);
src/fm95.c
+52 -2
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@@ -3,6 +3,17 @@
#include "ini.h"
#include <stdbool.h>
// #define JDSCA // jontio's jdsca - for fun
#ifdef JDSCA
#define JDSCA_BITRATE 2400.0f // bits/sec
#define JDSCA_IF_FREQ 3000.0f // OQPSK IF carrier, Hz
#define JDSCA_ALPHA 0.75f // RRC excess bandwidth
#define JDSCA_BUFFER_BITS 40000 // bit_ring capacity
#define JDSCA_SUBCARRIER_MULT 64.0f // 64 * 1187.5 Hz = 76 kHz
#define JDSCA_LEVEL 0.045f // injection level, tune by ear/scope
#endif
#define DEFAULT_INI_PATH "/etc/fm95/fm95.conf"
#define buffer_maxlength 99960
@@ -86,6 +97,10 @@ typedef struct {
float rds_symbol[4];
uint8_t rds_last_bit[4];
iirfilt_rrrf rds_filter[4];
#ifdef JDSCA
OQPSKMod mod;
bit_ring_t jsca_bitring;
#endif
} FM95_Runtime;
typedef struct {
@@ -145,8 +160,15 @@ void cleanup_runtime(FM95_Runtime* runtime, const FM95_Config config) {
runtime->lpf_l = runtime->lpf_r = NULL;
} exit_stereo_encoder(&runtime->stencode);
for(int i = 0; i < 4; i++) free(runtime->rds_bitring[i].bits);
for(int i = 0; i < 4; i++) iirfilt_rrrf_destroy(runtime->rds_filter[i]);
for(int i = 0; i < 4; i++) {
free(runtime->rds_bitring[i].bits);
iirfilt_rrrf_destroy(runtime->rds_filter[i]);
}
#ifdef JDSCA
free(runtime->jsca_bitring.bits);
oqpsk_destroy(&runtime->mod);
#endif
}
void cleanup_audio_runtime(FM95_Runtime *rt, const FM95_Options options) {
@@ -266,6 +288,14 @@ int run_fm95(FM95_Config* config, FM95_Runtime* runtime, FM95_RunResult* result)
}
}
#ifdef JDSCA
{
float jsca_baseband = oqpsk_process(&runtime->mod);
float jsca_carrier = get_oscillator_cos_multiplier_ni(&runtime->osc, JDSCA_SUBCARRIER_MULT);
mpx += jsca_baseband * jsca_carrier * JDSCA_LEVEL;
}
#endif
mpx = bs412_compress(&runtime->bs412, audio, mpx+mpx_in[i], &temp_result.mpx_power);
temp_result.bs412_gain = runtime->bs412.gain;
@@ -454,6 +484,12 @@ void init_runtime(FM95_Runtime* runtime, const FM95_Config config) {
runtime->rds_filter[i] = iirfilt_rrrf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, 8, (2400.0f/config.sample_rate), 0.0f, 1.0f, 40.0f);
}
#ifdef JDSCA
bit_ring_init(&runtime->jsca_bitring, JDSCA_BUFFER_BITS);
oqpsk_init(&runtime->mod, JDSCA_IF_FREQ, (float)config.sample_rate,
JDSCA_BITRATE / 2.0f, JDSCA_ALPHA, &runtime->jsca_bitring);
#endif
}
#define BUF_SIZE 256
@@ -589,6 +625,20 @@ static void *handle_client(ipc_client_arg_t *arg) {
reply = (written < nbits) ? 2 : 0;
break;
}
#ifdef JDSCA
case 0xfd: {
uint8_t unpacked[8 * (BUF_SIZE - 1)];
size_t nbits = 0;
for (ssize_t i = 1; i < n; i++)
for (int b = 7; b >= 0; b--)
unpacked[nbits++] = (buf[i] >> b) & 1;
size_t written = bit_ring_write(&data->runtime->jsca_bitring, unpacked, nbits);
if (written < nbits)
fprintf(stderr, "jsca bitring overrun: dropped %zu of %zu bits\n", nbits - written, nbits);
reply = (written < nbits) ? 2 : 0;
break;
}
#endif
case 0xfe:
// Fetch config
send(fd, data->config, sizeof(FM95_Config), 0);