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demod_flex.c
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/*
* demod_flex.c
*
* Copyright (C) 2015 Craig Shelley (craig@microtron.org.uk)
*
* FLEX Radio Paging Decoder - Adapted from GNURadio for use with Multimon
*
* 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* Version 0.8.5v (08 Sep 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - Issue #78 - Found a problem in the length detection sequence, modified the if statement to ensure the message length is
* only checked for Aplha messages, the other types calculate thier length while decoding
* Version 0.8.4v (05 Sep 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - Found a bug in the code that was not handling multiple group messages within the same frame,
* and the long address bit was being miss treated in the same cases. Both issue have been fixed but further testing will help.
* Version 0.8.3v (22 Jun 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - I had previously tagged Group Messages as GPN message types,
* this was my own identification rather than a Flex standard type.
* Now that I have cleaned up all identified (so far) issues I have changed back to the correct Flex message type of ALN (Alpha).
* Version 0.8.2v (21 Jun 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - Fixed group messaging capcode issue - modified the Capcode Array to be int64_t rather than int (I was incorrectly casting the long to an int)
* Version 0.8.1v (16 Jun 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - Added Debugging to help track the group messaging issues
* - Improved Alpha output and removed several loops to improve CPU cycles
* Version 0.8v (08 Jun 2017)
* Modification made by Bruce Quinton (Zanoroy@gmail.com)
* - Added Group Messaging
* - Fixed Phase adjustments (phasing as part of Symbol identification)
* - Fixed Alpha numeric length adjustments to stop "Invalid Vector" errors
* - Fixed numeric message treatment
* - Fixed invalid identification of "unknown" messages
* - Added 3200 2 fsk identification to all more message types to be processed (this was a big deal for NZ)
* - Changed uint to int variables
*
*/
/* ---------------------------------------------------------------------- */
#include "multimon.h"
#include "filter.h"
#include "BCHCode.h"
#include <math.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
/* ---------------------------------------------------------------------- */
#define FREQ_SAMP 22050
#define FILTLEN 1
#define FLEX_SYNC_MARKER 0xA6C6AAAAul // Synchronisation code marker for FLEX
#define SLICE_THRESHOLD 0.667 // For 4 level code, levels 0 and 3 have 3 times the amplitude of levels 1 and 2, so quantise at 2/3
#define DC_OFFSET_FILTER 0.010 // DC Offset removal IIR filter response (seconds)
#define PHASE_LOCKED_RATE 0.150 // Correction factor for locked state
#define PHASE_UNLOCKED_RATE 0.150 // Correction factor for unlocked state
#define LOCK_LEN 24 // Number of symbols to check for phase locking (max 32)
#define IDLE_THRESHOLD 0 // Number of idle codewords allowed in data section
#define CAPCODES_INDEX 0
enum Flex_PageTypeEnum {
FLEX_PAGETYPE_SECURE,
FLEX_PAGETYPE_SHORT_INSTRUCTION,
FLEX_PAGETYPE_TONE,
FLEX_PAGETYPE_STANDARD_NUMERIC,
FLEX_PAGETYPE_SPECIAL_NUMERIC,
FLEX_PAGETYPE_ALPHANUMERIC,
FLEX_PAGETYPE_BINARY,
FLEX_PAGETYPE_NUMBERED_NUMERIC
};
enum Flex_StateEnum {
FLEX_STATE_SYNC1,
FLEX_STATE_FIW,
FLEX_STATE_SYNC2,
FLEX_STATE_DATA
};
struct Flex_Demodulator {
unsigned int sample_freq;
double sample_last;
int locked;
int phase;
unsigned int sample_count;
unsigned int symbol_count;
double envelope_sum;
int envelope_count;
uint64_t lock_buf;
int symcount[4];
int timeout;
int nonconsec;
unsigned int baud; // Current baud rate
};
struct Flex_GroupHandler {
int64_t aGroupCodes[17][1000];
int GroupFrame[17];
};
struct Flex_Modulation {
double symbol_rate;
double envelope;
double zero;
};
struct Flex_State {
unsigned int sync2_count;
unsigned int data_count;
unsigned int fiwcount;
enum Flex_StateEnum Current;
enum Flex_StateEnum Previous;
};
struct Flex_Sync {
unsigned int sync; // Outer synchronization code
unsigned int baud; // Baudrate of SYNC2 and DATA
unsigned int levels; // FSK encoding of SYNC2 and DATA
unsigned int polarity; // 0=Positive (Normal) 1=Negative (Inverted)
uint64_t syncbuf;
};
struct Flex_FIW {
unsigned int rawdata;
unsigned int checksum;
unsigned int cycleno;
unsigned int frameno;
unsigned int fix3;
};
struct Flex_Phase {
unsigned int buf[88];
int idle_count;
};
struct Flex_Data {
int phase_toggle;
unsigned int data_bit_counter;
struct Flex_Phase PhaseA;
struct Flex_Phase PhaseB;
struct Flex_Phase PhaseC;
struct Flex_Phase PhaseD;
};
struct Flex_Decode {
enum Flex_PageTypeEnum type;
int long_address;
int64_t capcode;
struct BCHCode * BCHCode;
};
struct Flex {
struct Flex_Demodulator Demodulator;
struct Flex_Modulation Modulation;
struct Flex_State State;
struct Flex_Sync Sync;
struct Flex_FIW FIW;
struct Flex_Data Data;
struct Flex_Decode Decode;
struct Flex_GroupHandler GroupHandler;
};
int is_alphanumeric_page(struct Flex * flex) {
if (flex==NULL) return 0;
return (flex->Decode.type == FLEX_PAGETYPE_ALPHANUMERIC ||
flex->Decode.type == FLEX_PAGETYPE_SECURE);
}
int is_numeric_page(struct Flex * flex) {
if (flex==NULL) return 0;
return (flex->Decode.type == FLEX_PAGETYPE_STANDARD_NUMERIC ||
flex->Decode.type == FLEX_PAGETYPE_SPECIAL_NUMERIC ||
flex->Decode.type == FLEX_PAGETYPE_NUMBERED_NUMERIC);
}
int is_tone_page(struct Flex * flex) {
if (flex==NULL) return 0;
return (flex->Decode.type == FLEX_PAGETYPE_TONE);
}
unsigned int count_bits(struct Flex * flex, unsigned int data) {
if (flex==NULL) return 0;
#ifdef USE_BUILTIN_POPCOUNT
return __builtin_popcount(data);
#else
unsigned int n = (data >> 1) & 0x77777777;
data = data - n;
n = (n >> 1) & 0x77777777;
data = data - n;
n = (n >> 1) & 0x77777777;
data = data - n;
data = (data + (data >> 4)) & 0x0f0f0f0f;
data = data * 0x01010101;
return data >> 24;
#endif
}
static int bch3121_fix_errors(struct Flex * flex, uint32_t * data_to_fix, char PhaseNo) {
if (flex==NULL) return -1;
int i=0;
int recd[31];
/*Convert the data pattern into an array of coefficients*/
unsigned int data=*data_to_fix;
for (i=0; i<31; i++) {
recd[i] = (data>>30)&1;
data<<=1;
}
/*Decode and correct the coefficients*/
int decode_error=BCHCode_Decode(flex->Decode.BCHCode, recd);
/*Decode successful?*/
if (!decode_error) {
/*Convert the coefficient array back to a bit pattern*/
data=0;
for (i=0; i<31; i++) {
data<<=1;
data|=recd[i];
}
/*Count the number of fixed errors*/
int fixed=count_bits(flex, (*data_to_fix & 0x7FFFFFFF) ^ data);
if (fixed>0) {
verbprintf(3, "FLEX: Phase %c Fixed %i errors @ 0x%08x (0x%08x -> 0x%08x)\n", PhaseNo, fixed, (*data_to_fix&0x7FFFFFFF) ^ data, (*data_to_fix&0x7FFFFFFF), data );
}
/*Write the fixed data back to the caller*/
*data_to_fix=data;
} else {
verbprintf(3, "FLEX: Phase %c Data corruption - Unable to fix errors.\n", PhaseNo);
}
return decode_error;
}
static unsigned int flex_sync_check(struct Flex * flex, uint64_t buf) {
if (flex==NULL) return 0;
// 64-bit FLEX sync code:
// AAAA:BBBBBBBB:CCCC
//
// Where BBBBBBBB is always 0xA6C6AAAA
// and AAAA^CCCC is 0xFFFF
//
// Specific values of AAAA determine what bps and encoding the
// packet is beyond the frame information word
//
// First we match on the marker field with a hamming distance < 4
// Then we match on the outer code with a hamming distance < 4
unsigned int marker = (buf & 0x0000FFFFFFFF0000ULL) >> 16;
unsigned short codehigh = (buf & 0xFFFF000000000000ULL) >> 48;
unsigned short codelow = ~(buf & 0x000000000000FFFFULL);
int retval=0;
if (count_bits(flex, marker ^ FLEX_SYNC_MARKER) < 4 && count_bits(flex, codelow ^ codehigh) < 4 ) {
retval=codehigh;
} else {
retval=0;
}
return retval;
}
static unsigned int flex_sync(struct Flex * flex, unsigned char sym) {
if (flex==NULL) return 0;
int retval=0;
flex->Sync.syncbuf = (flex->Sync.syncbuf << 1) | ((sym < 2)?1:0);
retval=flex_sync_check(flex, flex->Sync.syncbuf);
if (retval!=0) {
flex->Sync.polarity=0;
} else {
/*If a positive sync pattern was not found, look for a negative (inverted) one*/
retval=flex_sync_check(flex, ~flex->Sync.syncbuf);
if (retval!=0) {
flex->Sync.polarity=1;
}
}
return retval;
}
static void decode_mode(struct Flex * flex, unsigned int sync_code) {
if (flex==NULL) return;
struct {
int sync;
unsigned int baud;
unsigned int levels;
} flex_modes[] = {
{ 0x870C, 1600, 2 },
{ 0xB068, 1600, 4 },
{ 0x7B18, 3200, 2 },
{ 0xDEA0, 3200, 4 },
{ 0x4C7C, 3200, 4 },
{0,0,0}
};
int x=0;
int i=0;
for (i=0; flex_modes[i].sync!=0; i++) {
if (count_bits(flex, flex_modes[i].sync ^ sync_code) < 4) {
flex->Sync.sync = sync_code;
flex->Sync.baud = flex_modes[i].baud;
flex->Sync.levels = flex_modes[i].levels;
x = 1;
break;
}
}
if(x==0){
verbprintf(3, "FLEX: Sync Code not found, defaulting to 1600bps 2FSK\n");
}
}
static void read_2fsk(struct Flex * flex, unsigned int sym, unsigned int * dat) {
if (flex==NULL) return;
*dat = (*dat >> 1) | ((sym > 1)?0x80000000:0);
}
static int decode_fiw(struct Flex * flex) {
if (flex==NULL) return -1;
unsigned int fiw = flex->FIW.rawdata;
int decode_error = bch3121_fix_errors(flex, &fiw, 'F');
if (decode_error) {
verbprintf(3, "FLEX: Unable to decode FIW, too much data corruption\n");
return 1;
}
// The only relevant bits in the FIW word for the purpose of this function
// are those masked by 0x001FFFFF.
flex->FIW.checksum = fiw & 0xF;
flex->FIW.cycleno = (fiw >> 4) & 0xF;
flex->FIW.frameno = (fiw >> 8) & 0x7F;
flex->FIW.fix3 = (fiw >> 15) & 0x3F;
unsigned int checksum = (fiw & 0xF);
checksum += ((fiw >> 4) & 0xF);
checksum += ((fiw >> 8) & 0xF);
checksum += ((fiw >> 12) & 0xF);
checksum += ((fiw >> 16) & 0xF);
checksum += ((fiw >> 20) & 0x01);
checksum &= 0xF;
if (checksum == 0xF) {
int timeseconds = flex->FIW.cycleno*4*60 + flex->FIW.frameno*4*60/128;
verbprintf(2, "FLEX: FrameInfoWord: cycleno=%02i frameno=%03i fix3=0x%02x time=%02i:%02i\n",
flex->FIW.cycleno,
flex->FIW.frameno,
flex->FIW.fix3,
timeseconds/60,
timeseconds%60);
return 0;
} else {
verbprintf(3, "FLEX: Bad Checksum 0x%x\n", checksum);
return 1;
}
}
static char* append_alphanumeric(char* buf, unsigned int dw) {
int i;
for (i = 0; i < 3; i++) {
unsigned char ch = (dw >> (i * 7)) & 0x7F;
if (ch && ch != 0x03) {
*buf = ch;
buf++;
}
}
return buf;
}
// static void parse_alphanumeric(struct Flex * flex, unsigned int * phaseptr, char PhaseNo, int mw1, int mw2, int j, int flex_groupmessage) {
static void parse_alphanumeric(struct Flex * flex, unsigned int * phaseptr, char PhaseNo, int mw1, int mw2, int flex_groupmessage) {
if (flex==NULL) return;
verbprintf(3, "FLEX: Parse Alpha Numeric\n");
int i;
time_t now=time(NULL);
struct tm * gmt=gmtime(&now);
char buf[1024], *message;
int frag = (phaseptr[mw1] >> 11) & 0x03;
if (frag == 0x3) {
// fragment shifts the message data up by one word
message = buf;
mw2++;
} else {
// ignore control data in first byte
message = append_alphanumeric(buf, phaseptr[mw1] & ~0x7F);
}
for (i = mw1+1; i < mw2; i++) {
message = append_alphanumeric(message, phaseptr[i]);
}
*message = '\0';
message = buf;
if (frag == 0x3) {
message++;
}
verbprintf(0, "FLEX: %04i-%02i-%02i %02i:%02i:%02i %i/%i/%c %02i.%03i [%09lld] ALN ", gmt->tm_year+1900, gmt->tm_mon+1, gmt->tm_mday, gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
flex->Sync.baud, flex->Sync.levels, PhaseNo, flex->FIW.cycleno, flex->FIW.frameno, flex->Decode.capcode);
verbprintf(0, "%s\n", message);
if(flex_groupmessage == 1) {
int groupbit = flex->Decode.capcode-2029568;
if(groupbit < 0) return;
int endpoint = flex->GroupHandler.aGroupCodes[groupbit][CAPCODES_INDEX];
for(int g = 1; g <= endpoint;g++)
{
verbprintf(1, "FLEX Group message output: Groupbit: %i Total Capcodes; %i; index %i; Capcode: [%09lld]\n", groupbit, endpoint, g, flex->GroupHandler.aGroupCodes[groupbit][g]);
verbprintf(0, "FLEX: %04i-%02i-%02i %02i:%02i:%02i %i/%i/%c %02i.%03i [%09lld] ALN ", gmt->tm_year+1900, gmt->tm_mon+1, gmt->tm_mday, gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
flex->Sync.baud, flex->Sync.levels, PhaseNo, flex->FIW.cycleno, flex->FIW.frameno, flex->GroupHandler.aGroupCodes[groupbit][g]);
verbprintf(0, "%s\n", message);
}
// reset the value
flex->GroupHandler.aGroupCodes[groupbit][CAPCODES_INDEX] = 0;
}
}
static void parse_numeric(struct Flex * flex, unsigned int * phaseptr, char PhaseNo, int j) {
if (flex==NULL) return;
unsigned const char flex_bcd[17] = "0123456789 U -][";
int w1 = phaseptr[j] >> 7;
int w2 = w1 >> 7;
w1 = w1 & 0x7f;
w2 = (w2 & 0x07) + w1; // numeric message is 7 words max
time_t now=time(NULL);
struct tm * gmt=gmtime(&now);
verbprintf(0, "FLEX: %04i-%02i-%02i %02i:%02i:%02i %i/%i/%c %02i.%03i [%09lld] NUM ", gmt->tm_year+1900, gmt->tm_mon+1, gmt->tm_mday, gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
flex->Sync.baud, flex->Sync.levels, PhaseNo, flex->FIW.cycleno, flex->FIW.frameno, flex->Decode.capcode);
// Get first dataword from message field or from second
// vector word if long address
int dw;
if(!flex->Decode.long_address) {
dw = phaseptr[w1];
w1++;
w2++;
} else {
dw = phaseptr[j+1];
}
unsigned char digit = 0;
int count = 4;
if(flex->Decode.type == FLEX_PAGETYPE_NUMBERED_NUMERIC) {
count += 10; // Skip 10 header bits for numbered numeric pages
} else {
count += 2; // Otherwise skip 2
}
int i;
for(i = w1; i <= w2; i++) {
int k;
for(k = 0; k < 21; k++) {
// Shift LSB from data word into digit
digit = (digit >> 1) & 0x0F;
if(dw & 0x01) {
digit ^= 0x08;
}
dw >>= 1;
if(--count == 0) {
if(digit != 0x0C) {// Fill
verbprintf(0, "%c", flex_bcd[digit]);
}
count = 4;
}
}
dw = phaseptr[i];
}
verbprintf(0, "\n");
}
static void parse_tone_only(struct Flex * flex, char PhaseNo) {
if (flex==NULL) return;
time_t now=time(NULL);
struct tm * gmt=gmtime(&now);
verbprintf(0, "FLEX: %04i-%02i-%02i %02i:%02i:%02i %i/%i/%c %02i.%03i [%09lld] TON\n", gmt->tm_year+1900, gmt->tm_mon+1, gmt->tm_mday, gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
flex->Sync.baud, flex->Sync.levels, PhaseNo, flex->FIW.cycleno, flex->FIW.frameno, flex->Decode.capcode);
}
static void parse_unknown(struct Flex * flex, unsigned int * phaseptr, char PhaseNo, int mw1, int mw2) {
if (flex==NULL) return;
time_t now=time(NULL);
struct tm * gmt=gmtime(&now);
verbprintf(0, "FLEX: %04i-%02i-%02i %02i:%02i:%02i %i/%i/%c %02i.%03i [%09lld] UNK", gmt->tm_year+1900, gmt->tm_mon+1, gmt->tm_mday, gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
flex->Sync.baud, flex->Sync.levels, PhaseNo, flex->FIW.cycleno, flex->FIW.frameno, flex->Decode.capcode);
int i;
for (i = mw1; i <= mw2; i++) {
verbprintf(0, " %08x", phaseptr[i]);
}
verbprintf(0, "\n");
}
//static void parse_capcode(struct Flex * flex, uint32_t aw1, uint32_t aw2) {
static void parse_capcode(struct Flex * flex, uint32_t aw1) {
if (flex==NULL) return;
flex->Decode.long_address = (aw1 < 0x008001L) ||
(aw1 > 0x1E0000L) ||
(aw1 > 0x1E7FFEL);
///if (flex->Decode.long_address)
// flex->Decode.capcode = (int64_t)aw1+((int64_t)(aw2^0x001FFFFFul)<<15)+0x1F9000ull; // Don't ask
//else
flex->Decode.capcode = aw1-0x8000;
}
static void decode_phase(struct Flex * flex, char PhaseNo) {
if (flex==NULL) return;
uint32_t *phaseptr=NULL;
int i, j;
switch (PhaseNo) {
case 'A': phaseptr=flex->Data.PhaseA.buf; break;
case 'B': phaseptr=flex->Data.PhaseB.buf; break;
case 'C': phaseptr=flex->Data.PhaseC.buf; break;
case 'D': phaseptr=flex->Data.PhaseD.buf; break;
}
for (i=0; i<88; i++) {
int decode_error=bch3121_fix_errors(flex, &phaseptr[i], PhaseNo);
if (decode_error) {
verbprintf(3, "FLEX: Garbled message at block %i\n", i);
return;
}
/*Extract just the message bits*/
phaseptr[i]&=0x001FFFFF;
}
// Block information word is the first data word in frame
uint32_t biw = phaseptr[0];
// Nothing to see here, please move along
if (biw == 0 || biw == 0x001FFFFF) {
verbprintf(3, "FLEX: Nothing to see here, please move along\n");
return;
}
// Vector start index is bits 15-10
// Address start address is bits 9-8, plus one for offset
int voffset = (biw >> 10) & 0x3f;
int aoffset = ((biw >> 8) & 0x03) + 1;
verbprintf(3, "FLEX: BlockInfoWord: (Phase %c) BIW:%08X AW:%02i-%02i (%i pages)\n", PhaseNo, biw, aoffset, voffset, voffset-aoffset);
int flex_groupmessage = 0;
// Iterate through pages and dispatch to appropriate handler
for (i = aoffset; i < voffset; i++) {
j = voffset+i-aoffset; // Start of vector field for address @ i
if (phaseptr[i] == 0x00000000 ||
phaseptr[i] == 0x001FFFFF) {
verbprintf(3, "FLEX: Idle codewords, invalid address\n");
continue; // Idle codewords, invalid address
}
parse_capcode(flex, phaseptr[i]);
// parse_capcode(flex, phaseptr[i], phaseptr[i+1]); // Older version maybe still needed so I'm not removing it (yet)
if (flex->Decode.long_address)
{
verbprintf(4, "FLEX: Found 'Long Address' bit, ignoring as I think this is handled incorrectly at the moment issue#79\n");
// i++;
}
if ((flex->Decode.capcode >= 2029568) && (flex->Decode.capcode <= 2029583)) {
flex_groupmessage = 1;
}
if (flex->Decode.capcode > 4297068542ll || flex->Decode.capcode < 0) { // Invalid address (by spec, maximum address)
verbprintf(3, "FLEX: Invalid address\n");
continue;
}
verbprintf(3, "FLEX: CAPCODE:%016lx\n", flex->Decode.capcode);
// Parse vector information word for address @ offset 'i'
uint32_t viw = phaseptr[j];
flex->Decode.type = ((viw >> 4) & 0x00000007);
int mw1 = (viw >> 7) & 0x00000007F;
int len = (viw >> 14) & 0x0000007F;
int w1 = (int)(viw >> 7);
int w2 = w1 >> 7;
w1 = w1 & 0x7f;
w2 = (w2 & 0x7f) + w1 - 1;
// int wL = w2 - w1;
if (flex->Decode.type == FLEX_PAGETYPE_SHORT_INSTRUCTION)
{
// if (flex_groupmessage == 1) continue;
int iAssignedFrame = (int)((viw >> 10) & 0x7f); // Frame with groupmessage
int groupbit = (int)((viw >> 17) & 0x7f); // Listen to this groupcode
flex->GroupHandler.aGroupCodes[groupbit][CAPCODES_INDEX]++;
int CapcodePlacement = flex->GroupHandler.aGroupCodes[groupbit][CAPCODES_INDEX];
verbprintf(1, "FLEX: Found Short Instruction, Group bit: %i capcodes in group so far %i, adding Capcode: [%09lld]\n", groupbit, CapcodePlacement, flex->Decode.capcode);
flex->GroupHandler.aGroupCodes[groupbit][CapcodePlacement] = flex->Decode.capcode;
flex->GroupHandler.GroupFrame[groupbit] = iAssignedFrame;
// Nothing else to do with this word.. move on!!
continue;
}
int mw2 = mw1+(len - 1);
if (mw1 == 0 && mw2 == 0){
verbprintf(3, "FLEX: Invalid VIW\n");
continue; // Invalid VIW
}
if (is_tone_page(flex))
mw1 = mw2 = 0;
// Check if this is an alpha message
if (is_alphanumeric_page(flex)) {
if (mw1 > 87 || mw2 > 87){
verbprintf(3, "FLEX: Invalid Offsets\n");
continue; // Invalid offsets
}
parse_alphanumeric(flex, phaseptr, PhaseNo, mw1, mw2, flex_groupmessage);
}
else if (is_numeric_page(flex))
parse_numeric(flex, phaseptr, PhaseNo, j);
else if (is_tone_page(flex))
parse_tone_only(flex, PhaseNo);
else
parse_unknown(flex, phaseptr, PhaseNo, mw1, mw2);
}
}
static void clear_phase_data(struct Flex * flex) {
if (flex==NULL) return;
int i;
for (i=0; i<88; i++) {
flex->Data.PhaseA.buf[i]=0;
flex->Data.PhaseB.buf[i]=0;
flex->Data.PhaseC.buf[i]=0;
flex->Data.PhaseD.buf[i]=0;
}
flex->Data.PhaseA.idle_count=0;
flex->Data.PhaseB.idle_count=0;
flex->Data.PhaseC.idle_count=0;
flex->Data.PhaseD.idle_count=0;
flex->Data.phase_toggle=0;
flex->Data.data_bit_counter=0;
}
static void decode_data(struct Flex * flex) {
if (flex==NULL) return;
if (flex->Sync.baud == 1600) {
if (flex->Sync.levels==2) {
decode_phase(flex, 'A');
} else {
decode_phase(flex, 'A');
decode_phase(flex, 'B');
}
} else {
if (flex->Sync.levels==2) {
decode_phase(flex, 'A');
decode_phase(flex, 'C');
} else {
decode_phase(flex, 'A');
decode_phase(flex, 'B');
decode_phase(flex, 'C');
decode_phase(flex, 'D');
}
}
}
static int read_data(struct Flex * flex, unsigned char sym) {
if (flex==NULL) return -1;
// Here is where we output a 1 or 0 on each phase according
// to current FLEX mode and symbol value. Unassigned phases
// are zero from the enter_idle() initialization.
//
// FLEX can transmit the data portion of the frame at either
// 1600 bps or 3200 bps, and can use either two- or four-level
// FSK encoding.
//
// At 1600 bps, 2-level, a single "phase" is transmitted with bit
// value '0' using level '3' and bit value '1' using level '0'.
//
// At 1600 bps, 4-level, a second "phase" is transmitted, and the
// di-bits are encoded with a gray code:
//
// Symbol Phase 1 Phase 2
// ------ ------- -------
// 0 1 1
// 1 1 0
// 2 0 0
// 3 0 1
//
// At 1600 bps, 4-level, these are called PHASE A and PHASE B.
//
// At 3200 bps, the same 1 or 2 bit encoding occurs, except that
// additionally two streams are interleaved on alternating symbols.
// Thus, PHASE A (and PHASE B if 4-level) are decoded on one symbol,
// then PHASE C (and PHASE D if 4-level) are decoded on the next.
int bit_a=0; //Received data bit for Phase A
int bit_b=0; //Received data bit for Phase B
bit_a = (sym > 1);
if (flex->Sync.levels == 4) {
bit_b = (sym == 1) || (sym == 2);
}
if (flex->Sync.baud == 1600) {
flex->Data.phase_toggle=0;
}
//By making the index scan the data words in this way, the data is deinterlaced
//Bits 0, 1, and 2 map straight through to give a 0-7 sequence that repeats 32 times before moving to 8-15 repeating 32 times
unsigned int idx= ((flex->Data.data_bit_counter>>5)&0xFFF8) | (flex->Data.data_bit_counter&0x0007);
if (flex->Data.phase_toggle==0) {
flex->Data.PhaseA.buf[idx] = (flex->Data.PhaseA.buf[idx]>>1) | (bit_a?(0x80000000):0);
flex->Data.PhaseB.buf[idx] = (flex->Data.PhaseB.buf[idx]>>1) | (bit_b?(0x80000000):0);
flex->Data.phase_toggle=1;
if ((flex->Data.data_bit_counter & 0xFF) == 0xFF) {
if (flex->Data.PhaseA.buf[idx] == 0x00000000 || flex->Data.PhaseA.buf[idx] == 0xffffffff) flex->Data.PhaseA.idle_count++;
if (flex->Data.PhaseB.buf[idx] == 0x00000000 || flex->Data.PhaseB.buf[idx] == 0xffffffff) flex->Data.PhaseB.idle_count++;
}
} else {
flex->Data.PhaseC.buf[idx] = (flex->Data.PhaseC.buf[idx]>>1) | (bit_a?(0x80000000):0);
flex->Data.PhaseD.buf[idx] = (flex->Data.PhaseD.buf[idx]>>1) | (bit_b?(0x80000000):0);
flex->Data.phase_toggle=0;
if ((flex->Data.data_bit_counter & 0xFF) == 0xFF) {
if (flex->Data.PhaseC.buf[idx] == 0x00000000 || flex->Data.PhaseC.buf[idx] == 0xffffffff) flex->Data.PhaseC.idle_count++;
if (flex->Data.PhaseD.buf[idx] == 0x00000000 || flex->Data.PhaseD.buf[idx] == 0xffffffff) flex->Data.PhaseD.idle_count++;
}
}
if (flex->Sync.baud == 1600 || flex->Data.phase_toggle==0) {
flex->Data.data_bit_counter++;
}
/*Report if all active phases have gone idle*/
int idle=0;
if (flex->Sync.baud == 1600) {
if (flex->Sync.levels==2) {
idle=(flex->Data.PhaseA.idle_count>IDLE_THRESHOLD);
} else {
idle=((flex->Data.PhaseA.idle_count>IDLE_THRESHOLD) && (flex->Data.PhaseB.idle_count>IDLE_THRESHOLD));
}
} else {
if (flex->Sync.levels==2) {
idle=((flex->Data.PhaseA.idle_count>IDLE_THRESHOLD) && (flex->Data.PhaseC.idle_count>IDLE_THRESHOLD));
} else {
idle=((flex->Data.PhaseA.idle_count>IDLE_THRESHOLD) && (flex->Data.PhaseB.idle_count>IDLE_THRESHOLD) && (flex->Data.PhaseC.idle_count>IDLE_THRESHOLD) && (flex->Data.PhaseD.idle_count>IDLE_THRESHOLD));
}
}
return idle;
}
static void report_state(struct Flex * flex) {
if (flex->State.Current != flex->State.Previous) {
flex->State.Previous = flex->State.Current;
char * state="Unknown";
switch (flex->State.Current) {
case FLEX_STATE_SYNC1:
state="SYNC1";
break;
case FLEX_STATE_FIW:
state="FIW";
break;
case FLEX_STATE_SYNC2:
state="SYNC2";
break;
case FLEX_STATE_DATA:
state="DATA";
break;
default:
break;
}
verbprintf(1, "FLEX: State: %s\n", state);
}
}
//Called for each received symbol
static void flex_sym(struct Flex * flex, unsigned char sym) {
if (flex==NULL) return;
/*If the signal has a negative polarity, the symbols must be inverted*/
/*Polarity is determined during the IDLE/sync word checking phase*/
unsigned char sym_rectified;
if (flex->Sync.polarity) {
sym_rectified=3-sym;
} else {
sym_rectified=sym;
}
switch (flex->State.Current) {
case FLEX_STATE_SYNC1:
{
// Continually compare the received symbol stream
// against the known FLEX sync words.
unsigned int sync_code=flex_sync(flex, sym); //Unrectified version of the symbol must be used here
if (sync_code!=0) {
decode_mode(flex,sync_code);
if (flex->Sync.baud!=0 && flex->Sync.levels!=0) {
flex->State.Current=FLEX_STATE_FIW;
verbprintf(2, "FLEX: SyncInfoWord: sync_code=0x%04x baud=%i levels=%i polarity=%s zero=%f envelope=%f symrate=%f\n",
sync_code, flex->Sync.baud, flex->Sync.levels, flex->Sync.polarity?"NEG":"POS", flex->Modulation.zero, flex->Modulation.envelope, flex->Modulation.symbol_rate);
} else {
verbprintf(2, "FLEX: Unknown Sync code = 0x%04x\n", sync_code);
flex->State.Current=FLEX_STATE_SYNC1;
}
} else {
flex->State.Current=FLEX_STATE_SYNC1;
}
flex->State.fiwcount=0;
flex->FIW.rawdata=0;
break;
}
case FLEX_STATE_FIW:
{
// Skip 16 bits of dotting, then accumulate 32 bits
// of Frame Information Word.
// FIW is accumulated, call BCH to error correct it
flex->State.fiwcount++;
if (flex->State.fiwcount>=16) {
read_2fsk(flex, sym_rectified, &flex->FIW.rawdata);
}
if (flex->State.fiwcount==48) {
if (decode_fiw(flex)==0) {
flex->State.sync2_count=0;
flex->Demodulator.baud = flex->Sync.baud;
flex->State.Current=FLEX_STATE_SYNC2;
} else {
flex->State.Current=FLEX_STATE_SYNC1;
}
}
break;
}
case FLEX_STATE_SYNC2:
{
// This part and the remainder of the frame are transmitted
// at either 1600 bps or 3200 bps based on the received
// FLEX sync word. The second SYNC header is 25ms of idle bits
// at either speed.
// Skip 25 ms = 40 bits @ 1600 bps, 80 @ 3200 bps
if (++flex->State.sync2_count == flex->Sync.baud*25/1000) {
flex->State.data_count=0;
clear_phase_data(flex);
flex->State.Current=FLEX_STATE_DATA;
}
break;
}
case FLEX_STATE_DATA:
{
// The data portion of the frame is 1760 ms long at either
// baudrate. This is 2816 bits @ 1600 bps and 5632 bits @ 3200 bps.
// The output_symbol() routine decodes and doles out the bits
// to each of the four transmitted phases of FLEX interleaved codes.
int idle=read_data(flex, sym_rectified);
if (++flex->State.data_count == flex->Sync.baud*1760/1000 || idle) {
decode_data(flex);
flex->Demodulator.baud = 1600;
flex->State.Current=FLEX_STATE_SYNC1;
flex->State.data_count=0;
}
break;
}
}
}
int buildSymbol(struct Flex * flex, double sample) {
if (flex == NULL) return 0;
const int64_t phase_max = 100 * flex->Demodulator.sample_freq; // Maximum value for phase (calculated to divide by sample frequency without remainder)
const int64_t phase_rate = phase_max*flex->Demodulator.baud / flex->Demodulator.sample_freq; // Increment per baseband sample
const double phasepercent = 100.0 * flex->Demodulator.phase / phase_max;
/*Update the sample counter*/
flex->Demodulator.sample_count++;
/*Remove DC offset (FIR filter)*/
if (flex->State.Current == FLEX_STATE_SYNC1) {
flex->Modulation.zero = (flex->Modulation.zero*(FREQ_SAMP*DC_OFFSET_FILTER) + sample) / ((FREQ_SAMP*DC_OFFSET_FILTER) + 1);
}
sample -= flex->Modulation.zero;
if (flex->Demodulator.locked) {
/*During the synchronisation period, establish the envelope of the signal*/
if (flex->State.Current == FLEX_STATE_SYNC1) {
flex->Demodulator.envelope_sum += fabs(sample);
flex->Demodulator.envelope_count++;
flex->Modulation.envelope = flex->Demodulator.envelope_sum / flex->Demodulator.envelope_count;
}
}
else {
/*Reset and hold in initial state*/
flex->Modulation.envelope = 0;
flex->Demodulator.envelope_sum = 0;
flex->Demodulator.envelope_count = 0;
flex->Demodulator.baud = 1600;
flex->Demodulator.timeout = 0;
flex->Demodulator.nonconsec = 0;
flex->State.Current = FLEX_STATE_SYNC1;
}
/* MID 80% SYMBOL PERIOD */
if (phasepercent > 10 && phasepercent <90) {
/*Count the number of occurrences of each symbol value for analysis at end of symbol period*/
if (sample > 0) {
if (sample > flex->Modulation.envelope*SLICE_THRESHOLD)
flex->Demodulator.symcount[3]++;
else
flex->Demodulator.symcount[2]++;
}
else {
if (sample < -flex->Modulation.envelope*SLICE_THRESHOLD)
flex->Demodulator.symcount[0]++;
else
flex->Demodulator.symcount[1]++;
}
}
/* ZERO CROSSING */
if ((flex->Demodulator.sample_last<0 && sample >= 0) || (flex->Demodulator.sample_last >= 0 && sample<0)) {
/*The phase error has a direction towards the closest symbol boundary*/
double phase_error = 0.0;
if (phasepercent<50) {
phase_error = flex->Demodulator.phase;
}