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Be more selective about what is flagged as TIS-B.

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This commit is contained in:
Oliver Jowett 2016-01-24 19:09:30 +00:00
parent 2b466535de
commit 2a07897354
1 changed files with 11 additions and 7 deletions
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18
mode_s.c
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@ -714,32 +714,36 @@ static void decodeExtendedSquitter(struct modesMessage *mm)
// Check CF on DF18 to work out the format of the ES and whether we need to look for an IMF bit // Check CF on DF18 to work out the format of the ES and whether we need to look for an IMF bit
if (mm->msgtype == 18) { if (mm->msgtype == 18) {
/* we just globally tag any DF18 as TIS-B,
* which is not strictly true but close enough
*/
mm->bFlags |= MODES_ACFLAGS_FROM_TISB;
switch (mm->cf) { switch (mm->cf) {
case 0: // ADS-B ES/NT devices that report the ICAO 24-bit address in the AA field case 0: // ADS-B ES/NT devices that report the ICAO 24-bit address in the AA field
break; break;
case 1: // Reserved for ADS-B for ES/NT devices that use other addressing techniques in the AA field case 1: // Reserved for ADS-B for ES/NT devices that use other addressing techniques in the AA field
case 5: // TIS-B messages that relay ADS-B Messages using anonymous 24-bit addresses (format not explicitly defined, but it seems to follow DF17)
mm->addr |= MODES_NON_ICAO_ADDRESS; mm->addr |= MODES_NON_ICAO_ADDRESS;
break; break;
case 2: // Fine TIS-B message (formats are close enough to DF17 for our purposes) case 2: // Fine TIS-B message (formats are close enough to DF17 for our purposes)
case 6: // ADS-B rebroadcast using the same type codes and message formats as defined for DF = 17 ADS-B messages mm->bFlags |= MODES_ACFLAGS_FROM_TISB;
check_imf = 1; check_imf = 1;
break; break;
case 3: // Coarse TIS-B airborne position and velocity. case 3: // Coarse TIS-B airborne position and velocity.
// TODO: decode me. // TODO: decode me.
// For now we only look at the IMF bit. // For now we only look at the IMF bit.
mm->bFlags |= MODES_ACFLAGS_FROM_TISB;
if (msg[4] & 0x80) if (msg[4] & 0x80)
mm->addr |= MODES_NON_ICAO_ADDRESS; mm->addr |= MODES_NON_ICAO_ADDRESS;
return; return;
case 5: // TIS-B messages that relay ADS-B Messages using anonymous 24-bit addresses (format not explicitly defined, but it seems to follow DF17)
mm->bFlags |= MODES_ACFLAGS_FROM_TISB;
mm->addr |= MODES_NON_ICAO_ADDRESS;
break;
case 6: // ADS-B rebroadcast using the same type codes and message formats as defined for DF = 17 ADS-B messages
check_imf = 1;
break;
default: // All others, we don't know the format. default: // All others, we don't know the format.
mm->addr |= MODES_NON_ICAO_ADDRESS; // assume non-ICAO mm->addr |= MODES_NON_ICAO_ADDRESS; // assume non-ICAO
return; return;