Kyle Keen
13 years ago
committed by
Steve Markgraf
parent
9d0232385b
commit
6328e11da6
@ -0,0 +1,361 @@ |
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/*
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* rtl-sdr, turns your Realtek RTL2832 based DVB dongle into a SDR receiver |
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* Copyright (C) 2012 by Steve Markgraf <steve@steve-m.de> |
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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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/*
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* written because people could not do real time |
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* FM demod on Atom hardware with GNU radio |
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* based on rtl_sdr.c |
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* todo: realtime ARMv5 |
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* remove float math (disqualifies complex.h) |
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* replace atan2 with a fast approximation |
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* in-place array operations |
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* wide band support |
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* squelch |
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* better threading |
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*/ |
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#include <errno.h> |
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#include <signal.h> |
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#include <string.h> |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <math.h> |
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#ifndef _WIN32 |
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#include <unistd.h> |
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#else |
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#include <Windows.h> |
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#endif |
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#include "rtl-sdr.h" |
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#define DEFAULT_SAMPLE_RATE 24000 |
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#define DEFAULT_ASYNC_BUF_NUMBER 32 |
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#define DEFAULT_BUF_LENGTH 1024 |
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#define MINIMAL_BUF_LENGTH 512 |
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#define MAXIMAL_BUF_LENGTH (256 * 16384) |
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static int do_exit = 0; |
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static rtlsdr_dev_t *dev = NULL; |
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struct fm_state |
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{ |
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int now_r; |
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int now_j; |
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int pre_r; |
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int pre_j; |
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int prev_index; |
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int downsample; /* min 4, max 256 */ |
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int output_scale; |
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int signal[2048]; /* 16 bit signed i/q pairs */ |
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int16_t signal2[2048]; /* signal has lowpass, signal2 has demod */ |
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int signal_len; |
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FILE *file; |
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}; |
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void usage(void) |
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{ |
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#ifdef _WIN32 |
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fprintf(stderr,"rtl_fm, a simple FM demodulator for RTL2832 based USB-sticks\n\n" |
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"Usage:\t rtl_fm-win.exe [device_index] [samplerate in kHz] " |
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"[gain] [frequency in Hz] [filename]\n"); |
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#else |
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fprintf(stderr, |
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"rtl_fm, a simple narrow band FM demodulator for RTL2832 based DVB-T receivers\n\n" |
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"Usage:\t -f frequency_to_tune_to [Hz]\n" |
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"\t[-s samplerate (default: 24000 Hz)]\n" |
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"\t[-d device_index (default: 0)]\n" |
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"\t[-g tuner_gain (default: -1dB)]\n" |
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"\tfilename (a '-' dumps samples to stdout)\n\n" |
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"Produces signed 16 bit ints, use sox to hear them.\n" |
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"\trtl_fm ... | play -t raw -r 24k -e signed-integer -b 16 -c 1 -\n\n"); |
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#endif |
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exit(1); |
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} |
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#ifdef _WIN32 |
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BOOL WINAPI |
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sighandler(int signum) |
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{ |
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if (CTRL_C_EVENT == signum) { |
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fprintf(stderr, "Signal caught, exiting!\n"); |
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do_exit = 1; |
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rtlsdr_cancel_async(dev); |
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return TRUE; |
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} |
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return FALSE; |
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} |
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#else |
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static void sighandler(int signum) |
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{ |
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fprintf(stderr, "Signal caught, exiting!\n"); |
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do_exit = 1; |
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rtlsdr_cancel_async(dev); |
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} |
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#endif |
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void rotate_90(unsigned char *buf, uint32_t len) |
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/* 90 rotation is 1+0j, 0+1j, -1+0j, 0-1j
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or [0, 1, -3, 2, -4, -5, 7, -6] */ |
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{ |
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uint32_t i; |
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unsigned char tmp; |
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for (i=0; i<len; i+=8) |
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{ |
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/* uint_8 negation = 255 - x */ |
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tmp = 255 - buf[i+3]; |
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buf[i+3] = buf[i+2]; |
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buf[i+2] = tmp; |
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buf[i+4] = 255 - buf[i+4]; |
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buf[i+5] = 255 - buf[i+5]; |
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tmp = 255 - buf[i+6]; |
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buf[i+6] = buf[i+7]; |
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buf[i+7] = tmp; |
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} |
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} |
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void low_pass(struct fm_state *fm, unsigned char *buf, uint32_t len) |
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{ |
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/* simple square window FIR */ |
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int i=0, i2=0; |
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while (i < (int)len) { |
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fm->now_r += ((int)buf[i] - 128); |
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fm->now_j += ((int)buf[i+1] - 128); |
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i += 2; |
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fm->prev_index++; |
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if (fm->prev_index < (fm->downsample)) { |
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continue; |
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} |
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fm->signal[i2] = fm->now_r * fm->output_scale; |
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fm->signal[i2+1] = fm->now_j * fm->output_scale; |
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fm->prev_index = -1; |
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fm->now_r = 0; |
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fm->now_j = 0; |
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i2 += 2; |
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} |
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fm->signal_len = i2; |
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} |
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/* define our own complex math ops
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because ARMv5 has no hardware float */ |
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void multiply(int ar, int aj, int br, int bj, int *cr, int *cj) |
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{ |
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*cr = ar*br - aj*bj; |
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*cj = aj*br + ar*bj; |
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} |
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int polar_discriminant(int ar, int aj, int br, int bj) |
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{ |
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int cr, cj; |
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double angle; |
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multiply(ar, aj, br, -bj, &cr, &cj); |
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/* fake squelch */ |
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//if (abs(cr) + abs(cj) < 50000)
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// {return 0;}
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angle = atan2((double)cj, (double)cr); |
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return (int)(angle / 3.14159 * (1<<14)); |
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} |
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void fm_demod(struct fm_state *fm) |
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{ |
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int i, pcm; |
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pcm = polar_discriminant(fm->signal[0], fm->signal[1], |
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fm->pre_r, fm->pre_j); |
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fm->signal2[0] = (int16_t)pcm; |
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for (i = 2; i < (fm->signal_len); i += 2) { |
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pcm = polar_discriminant(fm->signal[i], fm->signal[i+1], |
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fm->signal[i-2], fm->signal[i-1]); |
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fm->signal2[i/2] = (int16_t)pcm; |
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} |
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fm->pre_r = fm->signal[fm->signal_len - 2]; |
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fm->pre_j = fm->signal[fm->signal_len - 1]; |
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} |
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static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx) |
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{ |
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struct fm_state *fm2; |
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if (!ctx) { |
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return; |
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} |
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fm2 = (struct fm_struct*)(ctx); // bad conversion?
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rotate_90(buf, len); |
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low_pass(fm2, buf, len); |
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fm_demod(fm2); |
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/* ignore under runs for now */ |
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fwrite(fm2->signal2, 2, fm2->signal_len/2, fm2->file); |
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} |
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static void optimal_settings(struct fm_state *fm, int freq, int rate) |
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{ |
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int r, capture_freq, capture_rate; |
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fm->downsample = (1000000 / rate) + 1; |
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fprintf(stderr, "Oversampling by: %ix.\n", fm->downsample); |
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capture_rate = fm->downsample * rate; |
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capture_freq = freq + capture_rate/4; |
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fm->output_scale = (1<<15) / (128 * fm->downsample); |
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if (fm->output_scale < 1) { |
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fm->output_scale = 1; |
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} |
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fm->output_scale = 1; |
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/* Set the sample rate */ |
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r = rtlsdr_set_sample_rate(dev, capture_rate); |
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if (r < 0) |
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fprintf(stderr, "WARNING: Failed to set sample rate.\n"); |
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/* Set the frequency */ |
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r = rtlsdr_set_center_freq(dev, capture_freq); |
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if (r < 0) |
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fprintf(stderr, "WARNING: Failed to set center freq.\n"); |
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else |
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fprintf(stderr, "Tuned to %u Hz.\n", capture_freq); |
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} |
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int main(int argc, char **argv) |
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{ |
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#ifndef _WIN32 |
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struct sigaction sigact; |
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#endif |
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struct fm_state fm;
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char *filename = NULL; |
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int n_read; |
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int r, opt; |
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int i, gain = -10; // tenths of a dB
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uint8_t *buffer; |
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uint32_t dev_index = 0; |
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uint32_t frequency = 100000000; |
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uint32_t samp_rate = DEFAULT_SAMPLE_RATE; |
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uint32_t out_block_size = DEFAULT_BUF_LENGTH; |
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int device_count; |
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char vendor[256], product[256], serial[256]; |
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#ifndef _WIN32 |
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while ((opt = getopt(argc, argv, "d:f:g:s:b:S::")) != -1) { |
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switch (opt) { |
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case 'd': |
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dev_index = atoi(optarg); |
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break; |
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case 'f': |
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frequency = (uint32_t)atof(optarg); |
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break; |
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case 'g': |
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gain = (int)(atof(optarg) * 10); |
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break; |
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case 's': |
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samp_rate = (uint32_t)atof(optarg); |
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break; |
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default: |
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usage(); |
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break; |
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} |
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} |
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if (argc <= optind) { |
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usage(); |
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} else { |
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filename = argv[optind]; |
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} |
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#else |
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if(argc <6) |
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usage(); |
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dev_index = atoi(argv[1]); |
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samp_rate = atoi(argv[2])*1000; |
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gain=(int)(atof(argv[3]) * 10); |
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frequency = atoi(argv[4]); |
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filename = argv[5]; |
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#endif |
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out_block_size = DEFAULT_BUF_LENGTH; |
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buffer = malloc(out_block_size * sizeof(uint8_t)); |
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device_count = rtlsdr_get_device_count(); |
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if (!device_count) { |
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fprintf(stderr, "No supported devices found.\n"); |
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exit(1); |
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} |
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fprintf(stderr, "Found %d device(s):\n", device_count); |
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for (i = 0; i < device_count; i++) { |
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rtlsdr_get_device_usb_strings(i, vendor, product, serial); |
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fprintf(stderr, " %d: %s, %s, SN: %s\n", i, vendor, product, serial); |
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} |
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fprintf(stderr, "\n"); |
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fprintf(stderr, "Using device %d: %s\n", |
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dev_index, rtlsdr_get_device_name(dev_index)); |
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r = rtlsdr_open(&dev, dev_index); |
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if (r < 0) { |
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fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dev_index); |
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exit(1); |
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} |
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#ifndef _WIN32 |
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sigact.sa_handler = sighandler; |
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sigemptyset(&sigact.sa_mask); |
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sigact.sa_flags = 0; |
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sigaction(SIGINT, &sigact, NULL); |
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sigaction(SIGTERM, &sigact, NULL); |
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sigaction(SIGQUIT, &sigact, NULL); |
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sigaction(SIGPIPE, &sigact, NULL); |
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#else |
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SetConsoleCtrlHandler( (PHANDLER_ROUTINE) sighandler, TRUE ); |
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#endif |
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optimal_settings(&fm, frequency, samp_rate); |
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/* Set the tuner gain */ |
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r = rtlsdr_set_tuner_gain(dev, gain); |
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if (r < 0) |
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fprintf(stderr, "WARNING: Failed to set tuner gain.\n"); |
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else |
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fprintf(stderr, "Tuner gain set to %0.2f dB.\n", gain/10.0); |
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if(strcmp(filename, "-") == 0) { /* Write samples to stdout */ |
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fm.file = stdout; |
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} else { |
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fm.file = fopen(filename, "wb"); |
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if (!fm.file) { |
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fprintf(stderr, "Failed to open %s\n", filename); |
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goto out; |
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} |
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} |
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/* Reset endpoint before we start reading from it (mandatory) */ |
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r = rtlsdr_reset_buffer(dev); |
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if (r < 0) |
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fprintf(stderr, "WARNING: Failed to reset buffers.\n"); |
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fprintf(stderr, "Reading samples in async mode...\n"); |
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r = rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm), |
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DEFAULT_ASYNC_BUF_NUMBER, out_block_size); |
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if (do_exit) |
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fprintf(stderr, "\nUser cancel, exiting...\n"); |
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else |
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fprintf(stderr, "\nLibrary error %d, exiting...\n", r); |
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if (fm.file != stdout) |
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fclose(fm.file); |
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rtlsdr_close(dev); |
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free (buffer); |
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out: |
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return r >= 0 ? r : -r; |
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} |
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