mwalbeck/rtl_433
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Refactor baseband sample processing functions into own file

Browse source
This commit is contained in:
Tommy Vestermark 2015-08-09 13:08:37 +02:00
parent 37d51eca76
commit a9b0411ca8
5 changed files with 143 additions and 64 deletions

39
include/baseband.h Normal file
View file

@ -0,0 +1,39 @@
/**
* Baseband
*
* Various functions for baseband sample processing
*
* Copyright (C) 2012 by Benjamin Larsson <benjamin@southpole.se>
* Copyright (C) 2015 Tommy Vestermark
*
* 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.
*/
#ifndef INCLUDE_BASEBAND_H_
#define INCLUDE_BASEBAND_H_
#include <stdint.h>
/** This will give a noisy envelope of OOK/ASK signals
* Subtract the bias (-128) and get an envelope estimation
* The output will be written in the input buffer
* @returns pointer to the input buffer
*/
void envelope_detect(unsigned char *buf, uint32_t len, int decimate);
#define FILTER_ORDER 1
/// Lowpass filter
void low_pass_filter(uint16_t *x_buf, int16_t *y_buf, uint32_t len);
/// Initialize tables and constants
/// Should be called once at startup
void baseband_init(void);
/// Dump binary data (for debug purposes)
void baseband_dumpfile(uint8_t *buf, uint32_t len);
#endif /* INCLUDE_BASEBAND_H_ */

1
include/rtl_433.h
View file

@ -31,7 +31,6 @@
#define DEFAULT_DECIMATION_LEVEL 0
#define MINIMAL_BUF_LENGTH 512
#define MAXIMAL_BUF_LENGTH (256 * 16384)
#define FILTER_ORDER 1
#define MAX_PROTOCOLS 25
#define SIGNAL_GRABBER_BUFFER (12 * DEFAULT_BUF_LENGTH)

1
src/CMakeLists.txt
View file

@ -18,6 +18,7 @@
########################################################################
add_executable(rtl_433
rtl_433.c
baseband.c
bitbuffer.c
pulse_demod.c
pulse_detect.c

99
src/baseband.c Normal file
View file

@ -0,0 +1,99 @@
/**
* Baseband
*
* Various functions for baseband sample processing
*
* Copyright (C) 2012 by Benjamin Larsson <benjamin@southpole.se>
* Copyright (C) 2015 Tommy Vestermark
*
* 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.
*/
#include "baseband.h"
#include <stdio.h>
#include <string.h>
static uint16_t scaled_squares[256];
/* precalculate lookup table for envelope detection */
static void calc_squares() {
int i;
for (i = 0; i < 256; i++)
scaled_squares[i] = (128 - i) * (128 - i);
}
/** This will give a noisy envelope of OOK/ASK signals
* Subtract the bias (-128) and get an envelope estimation
* The output will be written in the input buffer
* @returns pointer to the input buffer
*/
void envelope_detect(unsigned char *buf, uint32_t len, int decimate) {
uint16_t* sample_buffer = (uint16_t*) buf;
unsigned int i;
unsigned op = 0;
unsigned int stride = 1 << decimate;
for (i = 0; i < len / 2; i += stride) {
sample_buffer[op++] = scaled_squares[buf[2 * i ]] + scaled_squares[buf[2 * i + 1]];
}
}
/** Something that might look like a IIR lowpass filter
*
* [b,a] = butter(1, 0.01) -> quantizes nicely thus suitable for fixed point
* Q1.15*Q15.0 = Q16.15
* Q16.15>>1 = Q15.14
* Q15.14 + Q15.14 + Q15.14 could possibly overflow to 17.14
* but the b coeffs are small so it wont happen
* Q15.14>>14 = Q15.0 \o/
*/
#define F_SCALE 15
#define S_CONST (1<<F_SCALE)
#define FIX(x) ((int)(x*S_CONST))
static uint16_t lp_xmem[FILTER_ORDER] = {0};
static int a[FILTER_ORDER + 1] = {FIX(1.00000), FIX(0.96907)};
static int b[FILTER_ORDER + 1] = {FIX(0.015466), FIX(0.015466)};
void low_pass_filter(uint16_t *x_buf, int16_t *y_buf, uint32_t len) {
unsigned int i;
/* Calculate first sample */
y_buf[0] = ((a[1] * y_buf[-1] >> 1) + (b[0] * x_buf[0] >> 1) + (b[1] * lp_xmem[0] >> 1)) >> (F_SCALE - 1);
for (i = 1; i < len; i++) {
y_buf[i] = ((a[1] * y_buf[i - 1] >> 1) + (b[0] * x_buf[i] >> 1) + (b[1] * x_buf[i - 1] >> 1)) >> (F_SCALE - 1);
}
/* Save last sample */
memcpy(lp_xmem, &x_buf[len - 1 - FILTER_ORDER], FILTER_ORDER * sizeof (int16_t));
memcpy(&y_buf[-FILTER_ORDER], &y_buf[len - 1 - FILTER_ORDER], FILTER_ORDER * sizeof (int16_t));
//fprintf(stderr, "%d\n", y_buf[0]);
}
void baseband_init(void) {
calc_squares();
}
static FILE *dumpfile = NULL;
void baseband_dumpfile(uint8_t *buf, uint32_t len) {
if (dumpfile == NULL) {
dumpfile = fopen("dumpfile.dat", "wb");
}
if (dumpfile == NULL) {
fprintf(stderr, "Error: could not open dumpfile.dat\n");
} else {
fwrite(buf, 1, len, dumpfile);
fflush(dumpfile); // Flush as file is not closed cleanly...
}
}

67
src/rtl_433.c
View file

@ -22,6 +22,7 @@
#include "rtl-sdr.h"
#include "rtl_433.h"
#include "baseband.h"
#include "pulse_detect.h"
#include "pulse_demod.h"
@ -34,7 +35,6 @@ int flag;
uint32_t samp_rate = DEFAULT_SAMPLE_RATE;
static uint32_t bytes_to_read = 0;
static rtlsdr_dev_t *dev = NULL;
static uint16_t scaled_squares[256];
static int override_short = 0;
static int override_long = 0;
int debug_output = 0;
@ -120,30 +120,6 @@ static void sighandler(int signum) {
}
#endif
/* precalculate lookup table for envelope detection */
static void calc_squares() {
int i;
for (i = 0; i < 256; i++)
scaled_squares[i] = (128 - i) * (128 - i);
}
/** This will give a noisy envelope of OOK/ASK signals
* Subtract the bias (-128) and get an envelope estimation
* The output will be written in the input buffer
* @returns pointer to the input buffer
*/
static void envelope_detect(unsigned char *buf, uint32_t len, int decimate) {
uint16_t* sample_buffer = (uint16_t*) buf;
unsigned int i;
unsigned op = 0;
unsigned int stride = 1 << decimate;
for (i = 0; i < len / 2; i += stride) {
sample_buffer[op++] = scaled_squares[buf[2 * i ]] + scaled_squares[buf[2 * i + 1]];
}
}
static void register_protocol(struct dm_state *demod, r_device *t_dev) {
struct protocol_state *p = calloc(1, sizeof (struct protocol_state));
@ -624,40 +600,6 @@ static void pwm_p_decode(struct dm_state *demod, struct protocol_state* p, int16
}
/** Something that might look like a IIR lowpass filter
*
* [b,a] = butter(1, 0.01) -> quantizes nicely thus suitable for fixed point
* Q1.15*Q15.0 = Q16.15
* Q16.15>>1 = Q15.14
* Q15.14 + Q15.14 + Q15.14 could possibly overflow to 17.14
* but the b coeffs are small so it wont happen
* Q15.14>>14 = Q15.0 \o/
*/
static uint16_t lp_xmem[FILTER_ORDER] = {0};
#define F_SCALE 15
#define S_CONST (1<<F_SCALE)
#define FIX(x) ((int)(x*S_CONST))
int a[FILTER_ORDER + 1] = {FIX(1.00000), FIX(0.96907)};
int b[FILTER_ORDER + 1] = {FIX(0.015466), FIX(0.015466)};
static void low_pass_filter(uint16_t *x_buf, int16_t *y_buf, uint32_t len) {
unsigned int i;
/* Calculate first sample */
y_buf[0] = ((a[1] * y_buf[-1] >> 1) + (b[0] * x_buf[0] >> 1) + (b[1] * lp_xmem[0] >> 1)) >> (F_SCALE - 1);
for (i = 1; i < len; i++) {
y_buf[i] = ((a[1] * y_buf[i - 1] >> 1) + (b[0] * x_buf[i] >> 1) + (b[1] * x_buf[i - 1] >> 1)) >> (F_SCALE - 1);
}
/* Save last sample */
memcpy(lp_xmem, &x_buf[len - 1 - FILTER_ORDER], FILTER_ORDER * sizeof (int16_t));
memcpy(&y_buf[-FILTER_ORDER], &y_buf[len - 1 - FILTER_ORDER], FILTER_ORDER * sizeof (int16_t));
//fprintf(stderr, "%d\n", y_buf[0]);
}
static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx) {
struct dm_state *demod = ctx;
uint16_t* sbuf = (uint16_t*) buf;
@ -684,7 +626,9 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx) {
if (demod->debug_mode == 0) {
envelope_detect(buf, len, demod->decimation_level);
// baseband_dumpfile(buf, len); // Debug
low_pass_filter(sbuf, demod->f_buf, len >> (demod->decimation_level + 1));
// baseband_dumpfile(demod->f_buf, len); // Debug
} else if (demod->debug_mode == 1) {
memcpy(demod->f_buf, buf, len);
}
@ -795,7 +739,7 @@ int main(int argc, char **argv) {
memset(demod, 0, sizeof (struct dm_state));
/* initialize tables */
calc_squares();
baseband_init();
r_device devices[] = {
#define DECL(name) name,
@ -1020,9 +964,6 @@ int main(int argc, char **argv) {
//Always classify a signal at the end of the file
classify_signal();
fprintf(stderr, "Test mode file issued %d packets\n", i);
fprintf(stderr, "Filter coeffs used:\n");
fprintf(stderr, "a: %d %d\n", a[0], a[1]);
fprintf(stderr, "b: %d %d\n", b[0], b[1]);
exit(0);
}