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Improve CW decoding 

* Introduce the hysteresis option, in order the CW demodulator to adjust
properly the plateau length based on the WPM and any filtering that can
be used before

* Instead for a frame per word, now the CW decoder waits for 10 long
spaces before it commits a frame. With this way many words are placed on
the same frame telemetry decoding is easier
This commit is contained in:
Manolis Surligas 2018-12-09 00:57:15 +02:00
parent 5291e18032
commit 67ea02a248
7 changed files with 466 additions and 419 deletions
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9
grc/satnogs_cw_to_symbol.xml
View File

@ -3,7 +3,7 @@
<name>CW to Symbols</name>
<key>satnogs_cw_to_symbol</key>
<import>import satnogs</import>
<make>satnogs.cw_to_symbol($sampling_rate, $threshold, $conf_level, $wpm)</make>
<make>satnogs.cw_to_symbol($sampling_rate, $threshold, $conf_level, $wpm, $hysteresis)</make>
<callback>set_act_threshold($threshold)</callback>
<param>
@ -33,6 +33,13 @@
<type>int</type>
</param>
<param>
<name>Hysteresis</name>
<key>hysteresis</key>
<value>0</value>
<type>int</type>
</param>
<sink>
<name>act_threshold</name>
<type>message</type>

14
include/satnogs/cw_to_symbol.h
View File

@ -24,6 +24,9 @@
#include <satnogs/api.h>
#include <gnuradio/sync_block.h>
#define MIN_WPM 5
#define MAX_WPM 50
namespace gr
{
namespace satnogs
@ -65,10 +68,19 @@ namespace gr
* symbols
*
* @param wpm Morse code Words per Minute
*
* @param hysteresis this value represents the hysteresis of a possible
* filter used before the CW to Symbol block. For example if there is
* a moving average filter with x taps, the full power of the signal
* will be available after x samples. The total length of samples with
* maximum power will be 2*x less. Because the block searches for plateaus
* with proper durations, this filtering hysteresis should be known.
* If no such a filter is used, the hysteresis value should be set to zero.
*/
static cw_to_symbol::sptr
make (double sampling_rate, float threshold, float conf_level = 0.9,
size_t wpm = 20);
size_t wpm = 20,
size_t hysteresis = 0);
virtual void
set_act_threshold (float thrld) = 0;

7
include/satnogs/morse.h
View File

@ -2,7 +2,7 @@
/*
* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
*
* Copyright (C) 2016,2017
* Copyright (C) 2016-2018
* Libre Space Foundation <http://librespacefoundation.org/>
*
* This program is free software: you can redistribute it and/or modify
@ -22,8 +22,6 @@
#ifndef INCLUDE_SATNOGS_MORSE_H_
#define INCLUDE_SATNOGS_MORSE_H_
#define MIN_WPM 5
#define MAX_WPM 30
/**
* The different Morse symbols
*/
@ -32,7 +30,8 @@ typedef enum {
MORSE_DASH, //!< Morse dash (-) symbol
MORSE_INTRA_SPACE, //!< Space between dot and dash symbols
MORSE_S_SPACE, //!< Morse short space between characters
MORSE_L_SPACE //!<Morse long space between words
MORSE_L_SPACE, //!<Morse long space between words
MORSE_END_MSG_SPACE //!< End of message
} morse_symbol_t;

36
lib/cw_to_symbol_impl.cc
View File

@ -44,17 +44,19 @@ namespace gr
cw_to_symbol::sptr
cw_to_symbol::make (double sampling_rate, float threshold, float conf_level,
size_t wpm)
size_t wpm, size_t hysteresis)
{
return gnuradio::get_initial_sptr (
new cw_to_symbol_impl (sampling_rate, threshold, conf_level, wpm));
new cw_to_symbol_impl (sampling_rate, threshold, conf_level, wpm,
hysteresis));
}
/*
* The private constructor
*/
cw_to_symbol_impl::cw_to_symbol_impl (double sampling_rate, float threshold,
float conf_level, size_t wpm) :
float conf_level, size_t wpm,
size_t hysteresis) :
gr::sync_block ("cw_to_symbol",
gr::io_signature::make (1, 1, sizeof(float)),
gr::io_signature::make (0, 0, 0)),
@ -64,13 +66,13 @@ namespace gr
d_dot_samples ((1.2 / wpm) * sampling_rate),
d_window_size (0),
d_window_cnt (0),
d_idle_cnt (0),
d_dot_windows_num (0),
d_dec_state (NO_SYNC),
d_prev_space_symbol (true)
{
if (wpm < MIN_WPM) {
throw std::invalid_argument (
"Decoder can not handle such low WPM setting");
throw std::invalid_argument ("Decoder can not handle such low WPM setting");
}
if (wpm > MAX_WPM) {
@ -83,6 +85,10 @@ namespace gr
"Confidence level should be in the range [0.5, 1.0]");
}
if(hysteresis > d_dot_samples / 4) {
throw std::invalid_argument ("Too large hysteresis value");
}
message_port_register_in (pmt::mp ("act_threshold"));
message_port_register_out (pmt::mp ("out"));
@ -92,6 +98,13 @@ namespace gr
boost::bind (&cw_to_symbol_impl::set_act_threshold_msg_handler, this,
_1));
/*
* Reconsider the dot oulse duration based on the confidence level
* and hysteresis
*/
d_dot_samples = d_dot_samples - 2 * (hysteresis * conf_level);
/*
* Try to split the CW pulses in smaller windows for detecting faster
* a false alarm. As we use the window size for setting the history
@ -109,8 +122,8 @@ namespace gr
d_window_size++;
}
LOG_WARN("Dot symbol samples: %lu", d_dot_samples);
LOG_WARN("Window size: %lu", d_window_size);
LOG_DEBUG("Dot symbol samples: %lu", d_dot_samples);
LOG_DEBUG("Window size: %lu", d_window_size);
/* Set the duration of each symbol in multiples of the window size */
d_dot_windows_num = d_dot_samples / d_window_size;
@ -172,6 +185,7 @@ namespace gr
{
d_dec_state = NO_SYNC;
d_window_cnt = 0;
d_idle_cnt = 0;
}
inline void
@ -230,13 +244,19 @@ namespace gr
return i + 1;
}
}
d_idle_cnt += noutput_items / d_window_size;
if(d_idle_cnt > 10 * d_long_pause_windows_num) {
send_symbol_msg (MORSE_END_MSG_SPACE);
d_idle_cnt = 0;
}
return noutput_items;
}
/* From now one, we handle the input in multiples of a window */
for (i = 0; i < (size_t) noutput_items / d_window_size; i++) {
triggered = is_triggered (in + i * d_window_size, d_window_size);
switch(d_dec_state) {
switch (d_dec_state)
{
case SEARCH_DOT:
if (triggered) {
d_window_cnt++;

3
lib/cw_to_symbol_impl.h
View File

@ -45,6 +45,7 @@ namespace gr
size_t d_dot_samples;
size_t d_window_size;
size_t d_window_cnt;
size_t d_idle_cnt;
size_t d_dot_windows_num;
size_t d_dash_windows_num;
size_t d_short_pause_windows_num;
@ -84,7 +85,7 @@ namespace gr
public:
cw_to_symbol_impl (double sampling_rate, float threshold,
float conf_level, size_t wpm);
float conf_level, size_t wpm, size_t hysteresis);
~cw_to_symbol_impl ();
// Where all the action really happens

23
lib/morse_decoder_impl.cc
View File

@ -42,7 +42,6 @@ namespace gr
morse_decoder_impl::symbol_msg_handler (pmt::pmt_t msg)
{
bool res = false;
std::string str;
morse_symbol_t s;
s = (morse_symbol_t) pmt::to_long (msg);
@ -68,16 +67,21 @@ namespace gr
res = true;
break;
}
str = d_morse_tree.get_word ();
if (str.length () > d_min_frame_len) {
d_str = d_str.append(d_morse_tree.get_word ());
d_str = d_str.append(" ");
d_morse_tree.reset ();
message_port_pub (pmt::mp ("out"),
pmt::make_blob (str.c_str (), str.length ()));
}
break;
case MORSE_INTRA_SPACE:
/*Ignore it */
break;
case MORSE_END_MSG_SPACE:
if (d_str.length () > d_min_frame_len) {
d_morse_tree.reset ();
message_port_pub (pmt::mp ("out"),
pmt::make_blob (d_str.c_str (), d_str.length ()));
d_str = "";
}
break;
default:
LOG_ERROR("Unknown Morse symbol");
return;
@ -89,10 +93,10 @@ namespace gr
*/
if (!res) {
if (d_morse_tree.get_max_word_len () == d_morse_tree.get_word_len ()) {
str = d_morse_tree.get_word ();
d_str = d_morse_tree.get_word ();
d_morse_tree.reset ();
message_port_pub (pmt::mp ("out"),
pmt::make_blob (str.c_str (), str.length ()));
pmt::make_blob (d_str.c_str (), d_str.length ()));
}
}
}
@ -105,7 +109,8 @@ namespace gr
gr::block ("morse_decoder", gr::io_signature::make (0, 0, 0),
gr::io_signature::make (0, 0, 0)),
d_morse_tree (unrecognized_char),
d_min_frame_len (min_frame_len)
d_min_frame_len (min_frame_len),
d_str("")
{
/* Register the input and output msg handler */

19
lib/morse_decoder_impl.h
View File

@ -24,21 +24,24 @@
#include <satnogs/morse_decoder.h>
#include <satnogs/morse_tree.h>
namespace gr {
namespace satnogs {
namespace gr
{
namespace satnogs
{
class morse_decoder_impl : public morse_decoder
{
private:
morse_tree d_morse_tree;
size_t d_min_frame_len;
void
symbol_msg_handler(pmt::pmt_t msg);
public:
morse_decoder_impl (char unrecognized_char, size_t min_frame_len);
private:
morse_tree d_morse_tree;
size_t d_min_frame_len;
std::string d_str;
void
symbol_msg_handler (pmt::pmt_t msg);
};
} // namespace satnogs