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Call new error correction code. Instead of bit positions record no. of corrected bits.

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This commit is contained in:
Ulrich Kuehn 2013-05-12 17:57:26 +02:00
parent 6d5d7a4244
commit feab602088
1 changed files with 23 additions and 29 deletions
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52
dump1090.c
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@ -286,7 +286,7 @@ struct modesMessage {
int msgtype; // Downlink format # int msgtype; // Downlink format #
int crcok; // True if CRC was valid int crcok; // True if CRC was valid
uint32_t crc; // Message CRC uint32_t crc; // Message CRC
int errorbit; // Bit corrected. -1 if no bit corrected int correctedbits; // No. of bits corrected
uint32_t addr; // ICAO Address from bytes 1 2 and 3 uint32_t addr; // ICAO Address from bytes 1 2 and 3
int phase_corrected; // True if phase correction was applied int phase_corrected; // True if phase correction was applied
uint64_t timestampMsg; // Timestamp of the message uint64_t timestampMsg; // Timestamp of the message
@ -657,12 +657,7 @@ void dumpRawMessageJS(char *descr, unsigned char *msg,
int start = offset - padding; int start = offset - padding;
int end = offset + (MODES_PREAMBLE_SAMPLES)+(MODES_LONG_MSG_SAMPLES) - 1; int end = offset + (MODES_PREAMBLE_SAMPLES)+(MODES_LONG_MSG_SAMPLES) - 1;
FILE *fp; FILE *fp;
int j, fix1 = -1, fix2 = -1; int j;
if (fixable != -1) {
fix1 = fixable & 0xff;
if (fixable > 255) fix2 = fixable >> 8;
}
if ((fp = fopen("frames.js","a")) == NULL) { if ((fp = fopen("frames.js","a")) == NULL) {
fprintf(stderr, "Error opening frames.js: %s\n", strerror(errno)); fprintf(stderr, "Error opening frames.js: %s\n", strerror(errno));
@ -674,8 +669,8 @@ void dumpRawMessageJS(char *descr, unsigned char *msg,
fprintf(fp,"%d", j < 0 ? 0 : m[j]); fprintf(fp,"%d", j < 0 ? 0 : m[j]);
if (j != end) fprintf(fp,","); if (j != end) fprintf(fp,",");
} }
fprintf(fp,"], \"fix1\": %d, \"fix2\": %d, \"bits\": %d, \"hex\": \"", fprintf(fp,"], \"fixed\": %d, \"bits\": %d, \"hex\": \"",
fix1, fix2, modesMessageLenByType(msg[0]>>3)); fixable, modesMessageLenByType(msg[0]>>3));
for (j = 0; j < MODES_LONG_MSG_BYTES; j++) for (j = 0; j < MODES_LONG_MSG_BYTES; j++)
fprintf(fp,"\\x%02x",msg[j]); fprintf(fp,"\\x%02x",msg[j]);
fprintf(fp,"\"});\n"); fprintf(fp,"\"});\n");
@ -699,12 +694,10 @@ void dumpRawMessage(char *descr, unsigned char *msg,
{ {
int j; int j;
int msgtype = msg[0] >> 3; int msgtype = msg[0] >> 3;
int fixable = -1; int fixable = 0;
if (msgtype == 17) { if (msgtype == 17) {
fixable = fixSingleBitErrors(msg, MODES_LONG_MSG_BITS); fixable = fixBitErrors(msg, MODES_LONG_MSG_BITS);
if (fixable == -1)
fixable = fixTwoBitsErrors(msg, MODES_LONG_MSG_BITS);
} }
if (Modes.debug & MODES_DEBUG_JS) { if (Modes.debug & MODES_DEBUG_JS) {
@ -1067,7 +1060,7 @@ void decodeModeAMessage(struct modesMessage *mm, int ModeA)
// Not much else we can tell from a Mode A/C reply. // Not much else we can tell from a Mode A/C reply.
// Just fudge up a few bits to keep other code happy // Just fudge up a few bits to keep other code happy
mm->crcok = 1; mm->crcok = 1;
mm->errorbit = -1; mm->correctedbits = 0;
} }
/* ===================== Mode S detection and decoding ===================== */ /* ===================== Mode S detection and decoding ===================== */
@ -1712,7 +1705,7 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
// Get the message type ASAP as other operations depend on this // Get the message type ASAP as other operations depend on this
mm->msgtype = msg[0] >> 3; // Downlink Format mm->msgtype = msg[0] >> 3; // Downlink Format
mm->msgbits = modesMessageLenByType(mm->msgtype); mm->msgbits = modesMessageLenByType(mm->msgtype);
mm->errorbit = -1; // No errors fixed mm->correctedbits = 0; // No errors fixed
mm->phase_corrected = 0; mm->phase_corrected = 0;
mm->crc = modesChecksum(msg, mm->msgbits); mm->crc = modesChecksum(msg, mm->msgbits);
@ -1728,10 +1721,10 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
// using the results. Perhaps check the ICAO against known aircraft, and check // using the results. Perhaps check the ICAO against known aircraft, and check
// IID against known good IID's. That's a TODO. // IID against known good IID's. That's a TODO.
// //
mm->errorbit = fixSingleBitErrors(msg, mm->msgbits); mm->correctedbits = fixBitErrors(msg, mm->msgbits);
if ((mm->errorbit == -1) && (Modes.aggressive)) { //if ((mm->errorbit == -1) && (Modes.aggressive)) {
mm->errorbit = fixTwoBitsErrors(msg, mm->msgbits); // mm->errorbit = fixTwoBitsErrors(msg, mm->msgbits);
} //}
} }
// //
// Note that most of the other computation happens *after* we fix the // Note that most of the other computation happens *after* we fix the
@ -1751,7 +1744,7 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
mm->crcok = (mm->crc == 0); mm->crcok = (mm->crc == 0);
mm->addr = (msg[1] << 16) | (msg[2] << 8) | (msg[3]); mm->addr = (msg[1] << 16) | (msg[2] << 8) | (msg[3]);
if (-1 != mm->errorbit) { if (0 != mm->correctedbits) {
// DF 17 : if (error corrected) force crc = 0 but do not try to add this address // DF 17 : if (error corrected) force crc = 0 but do not try to add this address
// to the whitelist of recently seen ICAO addresses. // to the whitelist of recently seen ICAO addresses.
mm->crc = 0; mm->crc = 0;
@ -1997,8 +1990,8 @@ void displayModesMessage(struct modesMessage *mm) {
if (mm->msgtype < 32) if (mm->msgtype < 32)
printf("CRC: %06x (%s)\n", (int)mm->crc, mm->crcok ? "ok" : "wrong"); printf("CRC: %06x (%s)\n", (int)mm->crc, mm->crcok ? "ok" : "wrong");
if (mm->errorbit != -1) if (mm->correctedbits != 0)
printf("Single bit error fixed, bit %d\n", mm->errorbit); printf("No. of bit errors fixed: %d\n", mm->correctedbits);
if (mm->msgtype == 0) { // DF 0 if (mm->msgtype == 0) { // DF 0
printf("DF 0: Short Air-Air Surveillance.\n"); printf("DF 0: Short Air-Air Surveillance.\n");
@ -2470,16 +2463,17 @@ void detectModeS(uint16_t *m, uint32_t mlen) {
if (Modes.stats) { if (Modes.stats) {
if (mm.crcok || use_correction) { if (mm.crcok || use_correction) {
if (errors == 0) Modes.stat_demodulated++; if (errors == 0) Modes.stat_demodulated++;
if (mm.errorbit == -1) { if (mm.correctedbits == 0) {
if (mm.crcok) {Modes.stat_goodcrc++;} if (mm.crcok) {Modes.stat_goodcrc++;}
else {Modes.stat_badcrc++;} else {Modes.stat_badcrc++;}
} else { } else {
Modes.stat_badcrc++; Modes.stat_badcrc++;
Modes.stat_fixed++; Modes.stat_fixed++;
if (mm.errorbit < MODES_LONG_MSG_BITS) if (mm.correctedbits == 1) {
{Modes.stat_single_bit_fix++;} Modes.stat_single_bit_fix++;
else } else if (mm.correctedbits == 2) {
{Modes.stat_two_bits_fix++;} Modes.stat_two_bits_fix++;
}
} }
} }
} }
@ -2490,10 +2484,10 @@ void detectModeS(uint16_t *m, uint32_t mlen) {
dumpRawMessage("Demodulated with 0 errors", msg, m, j); dumpRawMessage("Demodulated with 0 errors", msg, m, j);
else if (Modes.debug & MODES_DEBUG_BADCRC && else if (Modes.debug & MODES_DEBUG_BADCRC &&
mm.msgtype == 17 && mm.msgtype == 17 &&
(!mm.crcok || mm.errorbit != -1)) (!mm.crcok || mm.correctedbits != 0))
dumpRawMessage("Decoded with bad CRC", msg, m, j); dumpRawMessage("Decoded with bad CRC", msg, m, j);
else if (Modes.debug & MODES_DEBUG_GOODCRC && mm.crcok && else if (Modes.debug & MODES_DEBUG_GOODCRC && mm.crcok &&
mm.errorbit == -1) mm.correctedbits == 0)
dumpRawMessage("Decoded with good CRC", msg, m, j); dumpRawMessage("Decoded with good CRC", msg, m, j);
} }