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rtl-sdr/src/rtl_fm.c

426 lines
10 KiB

/*
* rtl-sdr, turns your Realtek RTL2832 based DVB dongle into a SDR receiver
* Copyright (C) 2012 by Steve Markgraf <steve@steve-m.de>
*
* 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/>.
*/
/*
* written because people could not do real time
* FM demod on Atom hardware with GNU radio
* based on rtl_sdr.c
* todo: realtime ARMv5
* remove float math (disqualifies complex.h)
* replace atan2 with a fast approximation
* in-place array operations
* wide band support
* refactor to look like rtl_tcp
* multiple frequency scanning
*/
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#ifndef _WIN32
#include <unistd.h>
#else
#include <Windows.h>
#endif
#include "rtl-sdr.h"
#define DEFAULT_SAMPLE_RATE 24000
#define DEFAULT_ASYNC_BUF_NUMBER 32
#define DEFAULT_BUF_LENGTH 1024
#define MINIMAL_BUF_LENGTH 512
#define MAXIMAL_BUF_LENGTH (256 * 16384)
static int do_exit = 0;
static rtlsdr_dev_t *dev = NULL;
struct fm_state
{
int now_r;
int now_j;
int pre_r;
int pre_j;
int prev_index;
int downsample; /* min 4, max 256 */
int output_scale;
int squelch_level;
int signal[2048]; /* 16 bit signed i/q pairs */
int16_t signal2[2048]; /* signal has lowpass, signal2 has demod */
int signal_len;
FILE *file;
int edge;
uint32_t freqs[32];
int freq_len;
int freq_now;
uint32_t sample_rate;
};
void usage(void)
{
#ifdef _WIN32
fprintf(stderr,"rtl_fm, a simple FM demodulator for RTL2832 based USB-sticks\n\n"
"Usage:\t rtl_fm-win.exe [device_index] [samplerate in kHz] "
"[gain] [frequency in Hz] [filename]\n");
#else
fprintf(stderr,
"rtl_fm, a simple narrow band FM demodulator for RTL2832 based DVB-T receivers\n\n"
"Usage:\t -f frequency_to_tune_to [Hz]\n"
"\t (use multiple -f for scanning !!BROKEN!!)\n"
"\t[-s samplerate (default: 24000 Hz)]\n"
"\t[-d device_index (default: 0)]\n"
"\t[-g tuner_gain (default: -1dB)]\n"
"\t[-l squelch_level (default: 150)]\n"
"\t[-E freq sets lower edge (default: center)]\n"
"\tfilename (a '-' dumps samples to stdout)\n\n"
"Produces signed 16 bit ints, use sox to hear them.\n"
"\trtl_fm ... | play -t raw -r 24k -e signed-integer -b 16 -c 1 -\n\n");
#endif
exit(1);
}
#ifdef _WIN32
BOOL WINAPI
sighandler(int signum)
{
if (CTRL_C_EVENT == signum) {
fprintf(stderr, "Signal caught, exiting!\n");
do_exit = 1;
rtlsdr_cancel_async(dev);
return TRUE;
}
return FALSE;
}
#else
static void sighandler(int signum)
{
fprintf(stderr, "Signal caught, exiting!\n");
do_exit = 1;
rtlsdr_cancel_async(dev);
}
#endif
void rotate_90(unsigned char *buf, uint32_t len)
/* 90 rotation is 1+0j, 0+1j, -1+0j, 0-1j
or [0, 1, -3, 2, -4, -5, 7, -6] */
{
uint32_t i;
unsigned char tmp;
for (i=0; i<len; i+=8) {
/* uint8_t negation = 255 - x */
tmp = 255 - buf[i+3];
buf[i+3] = buf[i+2];
buf[i+2] = tmp;
buf[i+4] = 255 - buf[i+4];
buf[i+5] = 255 - buf[i+5];
tmp = 255 - buf[i+6];
buf[i+6] = buf[i+7];
buf[i+7] = tmp;
}
}
void low_pass(struct fm_state *fm, unsigned char *buf, uint32_t len)
{
/* simple square window FIR */
int i=0, i2=0;
while (i < (int)len) {
fm->now_r += ((int)buf[i] - 128);
fm->now_j += ((int)buf[i+1] - 128);
i += 2;
fm->prev_index++;
if (fm->prev_index < (fm->downsample)) {
continue;
}
fm->signal[i2] = fm->now_r * fm->output_scale;
fm->signal[i2+1] = fm->now_j * fm->output_scale;
fm->prev_index = -1;
fm->now_r = 0;
fm->now_j = 0;
i2 += 2;
}
fm->signal_len = i2;
}
/* define our own complex math ops
because ARMv5 has no hardware float */
void multiply(int ar, int aj, int br, int bj, int *cr, int *cj)
{
*cr = ar*br - aj*bj;
*cj = aj*br + ar*bj;
}
int polar_discriminant(int ar, int aj, int br, int bj)
{
int cr, cj;
double angle;
multiply(ar, aj, br, -bj, &cr, &cj);
angle = atan2((double)cj, (double)cr);
return (int)(angle / 3.14159 * (1<<14));
}
void fm_demod(struct fm_state *fm)
{
int i, pcm;
pcm = polar_discriminant(fm->signal[0], fm->signal[1],
fm->pre_r, fm->pre_j);
fm->signal2[0] = (int16_t)pcm;
for (i = 2; i < (fm->signal_len); i += 2) {
pcm = polar_discriminant(fm->signal[i], fm->signal[i+1],
fm->signal[i-2], fm->signal[i-1]);
fm->signal2[i/2] = (int16_t)pcm;
}
fm->pre_r = fm->signal[fm->signal_len - 2];
fm->pre_j = fm->signal[fm->signal_len - 1];
}
int mad(int *samples, int len, int step)
/* mean average deviation */
{
int i=0, sum=0, ave=0;
for (i=0; i<len; i+=step) {
sum += samples[i];
}
ave = sum / (len * step);
sum = 0;
for (i=0; i<len; i+=step) {
sum += abs(samples[i] - ave);
}
return sum / (len * step);
}
int post_squelch(struct fm_state *fm)
/* returns 1 for active signal, 0 for no signal */
{
int i, i2, dev_r, dev_j, len, sq_l;
/* only for small samples, big samples need chunk processing */
len = fm->signal_len;
sq_l = fm->squelch_level;
dev_r = mad(&(fm->signal[0]), len, 2);
dev_j = mad(&(fm->signal[1]), len, 2);
if ((dev_r > sq_l) || (dev_j > sq_l)) {
return 1;
}
/* weak signal, kill it entirely */
for (i=0; i<len; i++) {
fm->signal2[i/2] = 0;
}
return 0;
}
static void optimal_settings(struct fm_state *fm, int freq, int hopping)
{
int r, capture_freq, capture_rate;
fm->downsample = (1000000 / fm->sample_rate) + 1;
fm->freq_now = freq;
capture_rate = fm->downsample * fm->sample_rate;
capture_freq = fm->freqs[freq] + capture_rate/4;
capture_freq += fm->edge * fm->sample_rate / 2;
fm->output_scale = (1<<15) / (128 * fm->downsample);
if (fm->output_scale < 1) {
fm->output_scale = 1;}
fm->output_scale = 1;
/* Set the frequency */
r = rtlsdr_set_center_freq(dev, capture_freq);
if (hopping) {
return;}
fprintf(stderr, "Oversampling by: %ix.\n", fm->downsample);
if (r < 0) {
fprintf(stderr, "WARNING: Failed to set center freq.\n");}
else {
fprintf(stderr, "Tuned to %u Hz.\n", capture_freq);}
/* Set the sample rate */
r = rtlsdr_set_sample_rate(dev, capture_rate);
if (r < 0) {
fprintf(stderr, "WARNING: Failed to set sample rate.\n");}
}
static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
{
struct fm_state *fm2;
int sr, freq_next;
if (!ctx) {
return;
}
fm2 = (struct fm_struct*)(ctx); // warning?
rotate_90(buf, len);
low_pass(fm2, buf, len);
fm_demod(fm2);
sr = post_squelch(fm2);
/* ignore under runs for now */
fwrite(fm2->signal2, 2, fm2->signal_len/2, fm2->file);
if (fm2->freq_len > 1 && !sr) {
freq_next = (fm2->freq_now + 1) % fm2->freq_len;
optimal_settings(fm2, freq_next, 1);
rtlsdr_reset_buffer(dev);
//rtlsdr_read_async(dev, rtlsdr_callback, ctx,
// DEFAULT_ASYNC_BUF_NUMBER, DEFAULT_BUF_LENGTH);
//rtlsdr_wait_async(dev, rtlsdr_callback, (void *)0);
//rtlsdr_wait_async(dev, rtlsdr_callback, ctx);
}
}
int main(int argc, char **argv)
{
#ifndef _WIN32
struct sigaction sigact;
#endif
struct fm_state fm;
char *filename = NULL;
int n_read;
int r, opt;
int i, gain = -10; // tenths of a dB
uint8_t *buffer;
uint32_t dev_index = 0;
uint32_t out_block_size = DEFAULT_BUF_LENGTH;
int device_count;
char vendor[256], product[256], serial[256];
fm.freqs[0] = 100000000;
fm.sample_rate = DEFAULT_SAMPLE_RATE;
fm.squelch_level = 150;
fm.freq_len = 0;
#ifndef _WIN32
while ((opt = getopt(argc, argv, "d:f:g:s:b:l:E::")) != -1) {
switch (opt) {
case 'd':
dev_index = atoi(optarg);
break;
case 'f':
fm.freqs[fm.freq_len] = (uint32_t)atof(optarg);
fm.freq_len++;
break;
case 'g':
gain = (int)(atof(optarg) * 10);
break;
case 'l':
fm.squelch_level = (int)atof(optarg);
break;
case 's':
fm.sample_rate = (uint32_t)atof(optarg);
break;
case 'E':
fm.edge = 1;
break;
default:
usage();
break;
}
}
if (argc <= optind) {
usage();
} else {
filename = argv[optind];
}
#else
if(argc <6)
usage();
dev_index = atoi(argv[1]);
samp_rate = atoi(argv[2])*1000;
gain=(int)(atof(argv[3]) * 10);
fm.freqs[0] = atoi(argv[4]);
fm.freq_len = 1;
filename = argv[5];
#endif
out_block_size = DEFAULT_BUF_LENGTH;
buffer = malloc(out_block_size * sizeof(uint8_t));
device_count = rtlsdr_get_device_count();
if (!device_count) {
fprintf(stderr, "No supported devices found.\n");
exit(1);
}
fprintf(stderr, "Found %d device(s):\n", device_count);
for (i = 0; i < device_count; i++) {
rtlsdr_get_device_usb_strings(i, vendor, product, serial);
fprintf(stderr, " %d: %s, %s, SN: %s\n", i, vendor, product, serial);
}
fprintf(stderr, "\n");
fprintf(stderr, "Using device %d: %s\n",
dev_index, rtlsdr_get_device_name(dev_index));
r = rtlsdr_open(&dev, dev_index);
if (r < 0) {
fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dev_index);
exit(1);
}
#ifndef _WIN32
sigact.sa_handler = sighandler;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = 0;
sigaction(SIGINT, &sigact, NULL);
sigaction(SIGTERM, &sigact, NULL);
sigaction(SIGQUIT, &sigact, NULL);
sigaction(SIGPIPE, &sigact, NULL);
#else
SetConsoleCtrlHandler( (PHANDLER_ROUTINE) sighandler, TRUE );
#endif
optimal_settings(&fm, 0, 0);
/* Set the tuner gain */
r = rtlsdr_set_tuner_gain(dev, gain);
if (r < 0)
fprintf(stderr, "WARNING: Failed to set tuner gain.\n");
else
fprintf(stderr, "Tuner gain set to %0.2f dB.\n", gain/10.0);
if(strcmp(filename, "-") == 0) { /* Write samples to stdout */
fm.file = stdout;
} else {
fm.file = fopen(filename, "wb");
if (!fm.file) {
fprintf(stderr, "Failed to open %s\n", filename);
goto out;
}
}
/* Reset endpoint before we start reading from it (mandatory) */
r = rtlsdr_reset_buffer(dev);
if (r < 0)
fprintf(stderr, "WARNING: Failed to reset buffers.\n");
fprintf(stderr, "Reading samples in async mode...\n");
r = rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm),
DEFAULT_ASYNC_BUF_NUMBER, out_block_size);
if (do_exit)
fprintf(stderr, "\nUser cancel, exiting...\n");
else
fprintf(stderr, "\nLibrary error %d, exiting...\n", r);
if (fm.file != stdout)
fclose(fm.file);
rtlsdr_close(dev);
free (buffer);
out:
return r >= 0 ? r : -r;
}