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demod_morse.c
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demod_morse.c
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/*-----------------------------------------------------------------------
*
* demod_morse.c -- Morse/CW decoder
*
* Written and placed into the public domain by
* Elias Önal <morse@eliasoenal.com>
*
*-----------------------------------------------------------------------*/
#include "multimon.h"
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#define FREQ_SAMP 22050
#define SMOOTHING_MAGNITUDE 9
#define GAIN 1
#define SQUELCH 500
#define HOLDOFF_MS 10 // Compensate for ringing
#define AUTO_THRESHOLD_MULT 2/3
//#define AUTO_THRESHOLD_MULT 1/2
#define DEBUG 0
#define SHOW_FAILED_DECODES 1
#define SPAM_SAMPLES 0
#define SPAM_STATE 0
#define LOW 0
#define HIGH 1
#define DIT 0x1 //0b01 .
#define DAH 0x2 //0b10 -
#define NUM_ELEMENTS(x) (sizeof(x)/sizeof(x[0]))
// Threshold between: DITs and DAHs is 2*cw_dit_length
// GAPS and EOC is 2*cw_gap_length
// EOC and EOW is 5*cw_gap_length
int cw_dit_length = 50;
int cw_gap_length = 50;
int cw_threshold = 500;
bool cw_disable_auto_threshold = false;
bool cw_disable_auto_timing = false;
static const struct morse_codes
{
const uint64_t sequence;
const char* character;
} morse_codes[] =
{
// DITs are 0b01 and DAHs are 0b10
// List is sorted for binary search
// HexValue Character BinValue MORSE/CW
{0x0000, "<NULL>"}, // 0b0
{0x0001, "E"}, // 0b01 .
{0x0002, "T"}, // 0b10 -
{0x0005, "I"}, // 0b0101 ..
{0x0006, "A"}, // 0b0110 .-
{0x0009, "N"}, // 0b1001 -.
{0x000A, "M"}, // 0b1010 --
{0x0015, "S"}, // 0b010101 ...
{0x0016, "U"}, // 0b010110 ..-
{0x0019, "R"}, // 0b011001 .-.
{0x001A, "W"}, // 0b011010 .--
{0x0025, "D"}, // 0b100101 -..
{0x0026, "K"}, // 0b100110 -.-
{0x0029, "G"}, // 0b101001 --.
{0x002A, "O"}, // 0b101010 ---
{0x0055, "H"}, // 0b01010101 ....
{0x0056, "V"}, // 0b01010110 ...-
{0x0059, "F"}, // 0b01011001 ..-.
{0x005A, "Ü"}, // 0b01011010 ..-- wrong? *?
{0x0065, "L"}, // 0b01100101 .-..
{0x0066, "Ä"}, // 0b01100110 .-.-
{0x0069, "P"}, // 0b01101001 .--.
{0x006A, "J"}, // 0b01101010 .---
{0x0095, "B"}, // 0b10010101 -...
{0x0096, "X"}, // 0b10010110 -..-
{0x0099, "C"}, // 0b10011001 -.-.
{0x009A, "Y"}, // 0b10011010 -.--
{0x00A5, "Z"}, // 0b10100101 --..
{0x00A6, "Q"}, // 0b10100110 --.-
{0x00A9, "Ö"}, // 0b10101001 ---.
{0x00AA, "CH"}, // 0b10101010 ----
{0x0155, "5"}, // 0b0101010101 .....
{0x0156, "4"}, // 0b0101010110 ....-
{0x0159, "<SN>"}, // 0b0101011001 ...-.
{0x015A, "3"}, // 0b0101011010 ...--
{0x0166, "/"}, // 0b0101100110 ..-.-
{0x016A, "2"}, // 0b0101101010 ..---
{0x0195, "&"}, // 0b0110010101 .-...
{0x0199, "+"}, // 0b0110011001 .-.-.
{0x01AA, "1"}, // 0b0110101010 .----
{0x0255, "6"}, // 0b1001010101 -....
{0x0256, "="}, // 0b1001010110 -...-
{0x0266, "<CT>"}, // 0b1001100110 -.-.-
{0x0259, "/"}, // 0b1001011001 -..-. wrong?
{0x0269, "("}, // 0b1001101001 -.--.
{0x0295, "7"}, // 0b1010010101 --...
{0x02A5, "8"}, // 0b1010100101 ---..
{0x02A9, "9"}, // 0b1010101001 ----.
{0x02AA, "0"}, // 0b1010101010 -----
{0x0555, "<ERR_6>"}, // 0b010101010101 ......
{0x0566, "<SK>"}, // 0b010101100110 ...-.-
{0x05A5, "?"}, // 0b010110100101 ..--..
{0x05A6, "_"}, // 0b010110100110 ..--.-
{0x0659, "\""}, // 0b011001011001 .-..-.
{0x0666, "."}, // 0b011001100110 .-.-.-
{0x0699, "@"}, // 0b011010011001 .--.-.
{0x06A9, "'"}, // 0b011010101001 .----.
{0x0956, "-"}, // 0b100101010110 -....-
{0x096A, "<DO>"}, // 0b100101101010 -..---
{0x0999, ";"}, // 0b100110011001 -.-.-.
{0x099A, "!"}, // 0b100110011010 -.-.--
{0x09A6, ")"}, // 0b100110100110 -.--.-
{0x0A5A, ","}, // 0b101001011010 --..--
{0x0A95, ":"}, // 0b101010010101 ---...
{0x1555, "<ERR_7>"}, // 0b01010101010101 .......
{0x1596, "$"}, // 0b01010110010110 ...-..-
{0x2566, "<BK>"}, // 0b10010101100110 -...-.-
{0x5555, "<ERR_8>"}, // 0b0101010101010101 ........
{0x9965, "<CL>"}, // 0b1001100101100101 -.-..-..
{0x15555, "<ERR_9>"}, // 0b010101010101010101 .........
{0x15A95, "<SOS>"}, // 0b010101101010010101 ...---...
{0x55555, "<ERR_10>"},// 0b01010101010101010101 ..........
{0x155555, "<ERR_11>"},// 0b0101010101010101010101 ...........
{0x555555, "<ERR_12>"},// 0b0101010101010101(...) ......(...)
{0x1555555, "<ERR_13>"},// 0b0101010101010101(...) ......(...)
{0x5555555, "<ERR_14>"},// 0b0101010101010101(...) ......(...)
{0x15555555, "<ERR_15>"},// 0b0101010101010101(...) ......(...)
{0x55555555, "<ERR_16>"},// 0b0101010101010101(...) ......(...)
{0x155555555, "<ERR_17>"},// 0b0101010101010101(...) ......(...)
{0x555555555, "<ERR_18>"},// 0b0101010101010101(...) ......(...)
{0x1555555555, "<ERR_19>"},// 0b0101010101010101(...) ......(...)
{0x5555555555, "<ERR_20>"},// 0b0101010101010101(...) ......(...)
{0x15555555555, "<ERR_21>"},// 0b0101010101010101(...) ......(...)
{0x55555555555, "<ERR_22>"},// 0b0101010101010101(...) ......(...)
{0x155555555555, "<ERR_23>"},// 0b0101010101010101(...) ......(...)
{0x555555555555, "<ERR_24>"},// 0b0101010101010101(...) ......(...)
{0x1555555555555, "<ERR_25>"},// 0b0101010101010101(...) ......(...)
{0x5555555555555, "<ERR_26>"},// 0b0101010101010101(...) ......(...)
{0x15555555555555, "<ERR_27>"},// 0b0101010101010101(...) ......(...)
{0x55555555555555, "<ERR_28>"},// 0b0101010101010101(...) ......(...)
{0x155555555555555, "<ERR_29>"},// 0b0101010101010101(...) ......(...)
{0x555555555555555, "<ERR_30>"},// 0b0101010101010101(...) ......(...)
{0x1555555555555555,"<ERR_31>"},// 0b0101010101010101(...) ......(...)
{0x5555555555555555,"<ERR_32>"},// 0b0101010101010101(...) ......(...)
// Sequences longer than 32 DITs will overflow and show up as <ERR_32> as well.
};
typedef struct dec_ret_t
{
char* restrict string_ptr;
char string[32 + 3]; //32 dit/dahs + 2 brackets and 0
bool status;
} dec_ret_t;
// Binary search is crazy fast! 0.01% of our CPU time. O(log n) ftw!
static inline dec_ret_t decode_character(const struct demod_state * restrict const s)
{
int_fast16_t min = 0;
int_fast16_t max = NUM_ELEMENTS(morse_codes) - 1;
uint64_t sequence = s->l1.morse.current_sequence;
while (max >= min) // Search
{
int_fast16_t mid = (min + max) / 2;
if(morse_codes[mid].sequence > sequence) max = mid - 1;
else if(morse_codes[mid].sequence < sequence) min = mid + 1;
else{dec_ret_t rtn = {(char*)morse_codes[mid].character,"",true};
return rtn;}
}
// Build ASCII art from sequence
dec_ret_t rtn = {rtn.string,"",false};
*(rtn.string_ptr++) = '<';
char symbol;
for(int i = 0; i < (int)sizeof(sequence) * 8; i+=2)
if((symbol = (sequence >> (sizeof(sequence) - 2 - i)) & (0x3)))
*(rtn.string_ptr++) = (symbol == DIT)?'.':'_';
*(rtn.string_ptr++) = '>';
*rtn.string_ptr = '\0';
rtn.string_ptr = rtn.string;
return rtn;
}
// Low pass filter - eats 19.4% of the CPU time according to profiling
// It's a basic IIR filter optimized for integer operation while
// minimizing the rounding error.
static inline int_fast32_t low_pass(const int_fast32_t last_filtered,
const int_fast32_t new_sample,
const int_fast16_t strength)
{
return ((last_filtered << strength) +
new_sample - last_filtered) >> strength;
}
// Probably a lot room for improvements here
// Another 19.5% of our precious CPU time. It's optional though.
static inline void auto_threshold(struct demod_state * restrict const s)
{
// Hackish solution in order to have the threshold adjust.
// The highest known amplitude bleeds 20 times 0.1%, per second.
s->l1.morse.threshold_ctr = (s->l1.morse.threshold_ctr+1) % (FREQ_SAMP / 20);
if(!s->l1.morse.threshold_ctr && s->l1.morse.signal_max > 0)
{
s->l1.morse.signal_max = s->l1.morse.signal_max * 999 / 1000;
s->l1.morse.detection_threshold = s->l1.morse.signal_max*AUTO_THRESHOLD_MULT;
}
// Check for a higher upper limit
if(s->l1.morse.filtered > s->l1.morse.signal_max)
{
s->l1.morse.signal_max = s->l1.morse.filtered;
s->l1.morse.detection_threshold = s->l1.morse.signal_max*AUTO_THRESHOLD_MULT;
}
// Prevent threshold from dropping below SQUELCH
if(s->l1.morse.detection_threshold < SQUELCH)
s->l1.morse.detection_threshold = SQUELCH;
}
// TODO: Come up with a more fancy solution!
static inline void auto_timing(const bool state, struct demod_state * restrict const s)
{
if(s->l1.morse.samples_since_change < FREQ_SAMP / (1000 / 120)) //120ms
{
if(state == LOW)
{
if(s->l1.morse.time_unit_gaps_samples > s->l1.morse.samples_since_change)
s->l1.morse.time_unit_gaps_samples -= 50;
else s->l1.morse.time_unit_gaps_samples += 50;
}
else
{
if(s->l1.morse.time_unit_dit_dah_samples > s->l1.morse.samples_since_change)
s->l1.morse.time_unit_dit_dah_samples -= 50;
else s->l1.morse.time_unit_dit_dah_samples += 50;
}
}
}
// This one gets about 60% of our cycles.
static void morse_demod(struct demod_state * restrict const s,
const buffer_t buffer, const int length)
{
for(int i = 0; i < length; i++)
{
// A low-pass is nice, though we could add a high-pass in order to get a band-pass :)
// abs() when combined with the low-pass works as a peak detector
s->l1.morse.filtered = low_pass(s->l1.morse.filtered, (int_fast32_t)abs(buffer.sbuffer[i]) * GAIN,
s->l1.morse.lowpass_strength);
// Don't count too far
if(s->l1.morse.samples_since_change < INT_FAST32_MAX/1000)
s->l1.morse.samples_since_change++;
if(!cw_disable_auto_threshold) auto_threshold(s);
int_fast8_t oldstate = s->l1.morse.current_state;
// Reject change for holdoff period
if(s->l1.morse.samples_since_change > s->l1.morse.holdoff_samples)
s->l1.morse.current_state = s->l1.morse.filtered > s->l1.morse.detection_threshold;
if(SPAM_SAMPLES) verbprintf(0, " %d", s->l1.morse.filtered);
if(SPAM_STATE) verbprintf(0, " %s", s->l1.morse.current_state?"#":".");
int_fast8_t statechange = oldstate != s->l1.morse.current_state;
int_fast8_t timeout = s->l1.morse.samples_since_change == 5*s->l1.morse.time_unit_gaps_samples;
// Enter on state transition or timeout
if(statechange || timeout)
{
// Ignore glitches only lasting the holdoff period
if(s->l1.morse.samples_since_change == s->l1.morse.holdoff_samples+1)
{
if(DEBUG) verbprintf(0, "<GLITCH %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
s->l1.morse.glitches++;
goto reset_samples;
}
if(oldstate == LOW)
{
// Check whether it was just a inter DIT/DAH gap, else decode
if(s->l1.morse.samples_since_change >= 2*s->l1.morse.time_unit_gaps_samples)
{
dec_ret_t rtn = {NULL,"",false};
if(s->l1.morse.current_sequence)
{
rtn = decode_character(s);
if(SHOW_FAILED_DECODES) verbprintf(0, "%s", rtn.string_ptr);
else if(rtn.status) verbprintf(0, "%s", rtn.string_ptr);
if(rtn.status) s->l1.morse.decoded_chars++;
else s->l1.morse.erroneous_chars++;
s->l1.morse.current_sequence = 0; // Start a new sequence
}
if(s->l1.morse.samples_since_change < 5*s->l1.morse.time_unit_gaps_samples) // End of Char
{
if(DEBUG) verbprintf(0, "<EOC %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
}
else if(timeout) // End of word - timeout
{
if(rtn.status)
verbprintf(0," "); //Don't print additional spaces if last character failed to decode
if(DEBUG) verbprintf(0, "<EOW %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
goto end; // Don't reset samples, since there wasn't any change in state.
}
} // It was just a inter DIT/DAH gap
else if(DEBUG) verbprintf(0, "<GAP %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
}
else // Last state was either DIT or DAH
{
if(s->l1.morse.samples_since_change < 2*s->l1.morse.time_unit_dit_dah_samples)
{
s->l1.morse.current_sequence = (s->l1.morse.current_sequence << 2) | DIT;
if(DEBUG) verbprintf(0, "<DIT %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
}
else
{
s->l1.morse.current_sequence = (s->l1.morse.current_sequence << 2) | DAH;
if(DEBUG) verbprintf(0, "<DAH %dms>", s->l1.morse.samples_since_change * 1000 / FREQ_SAMP);
}
}
if(!cw_disable_auto_timing) auto_timing(oldstate, s);
reset_samples:
s->l1.morse.samples_since_change = 0; // State has changed, restart counting
end:;
}
}
}
static void morse_init(struct demod_state * restrict s)
{
memset(&s->l1.morse, 0, sizeof(s->l1.morse));
s->l1.morse.time_unit_dit_dah_samples = FREQ_SAMP / (1000 / cw_dit_length);
s->l1.morse.time_unit_gaps_samples = FREQ_SAMP / (1000 / cw_gap_length);
s->l1.morse.detection_threshold = cw_threshold;
s->l1.morse.lowpass_strength = SMOOTHING_MAGNITUDE;
if(HOLDOFF_MS) s->l1.morse.holdoff_samples = FREQ_SAMP / (1000 / HOLDOFF_MS);
s->l1.morse.signal_max = SQUELCH;
}
static void morse_deinit(struct demod_state * const restrict s)
{
verbprintf(1, "\nMAX: %d THRESHOLD: %d GLITCHES: %d FAILED: %d "
"DECODED: %d TIMING_GAP: %d TIMING_DIT: %d",
s->l1.morse.signal_max,
s->l1.morse.detection_threshold,
s->l1.morse.glitches,
s->l1.morse.erroneous_chars,
s->l1.morse.decoded_chars,
s->l1.morse.time_unit_gaps_samples * 1000 / FREQ_SAMP,
s->l1.morse.time_unit_dit_dah_samples * 1000 / FREQ_SAMP);
verbprintf(0, "\n");
}
const struct demod_param demod_morse = {
"MORSE_CW", false, FREQ_SAMP, 0, morse_init, morse_demod, morse_deinit
};